Butler’s Gartersnake recovery strategy

About the Ontario recovery strategy series

This series presents the collection of recovery strategies that are prepared or adopted as advice to the Province of Ontario on the recommended approach to recover species at risk. The Province ensures the preparation of recovery strategies to meet its commitments to recover species at risk under the Endangered Species Act, 2007 (ESA) and the Accord for the Protection of Species at Risk in Canada.

What is recovery?

Recovery of species at risk is the process by which the decline of an endangered, threatened, or extirpated species is arrested or reversed, and threats are removed or reduced to improve the likelihood of a species’ persistence in the wild.

What is a recovery strategy?

Under the ESA a recovery strategy provides the best available scientific knowledge on what is required to achieve recovery of a species. A recovery strategy outlines the habitat needs and the threats to the survival and recovery of the species. It also makes recommendations on the objectives for protection and recovery, the approaches to achieve those objectives, and the area that should be considered in the development of a habitat regulation. Sections 11 to 15 of the ESA outline the required content and timelines for developing recovery strategies published in this series.

Recovery strategies are required to be prepared for endangered and threatened species within one or two years respectively of the species being added to the Species at Risk in Ontario list. Recovery strategies are required to be prepared for extirpated species only if reintroduction is considered feasible.

What’s next?

Nine months after the completion of a recovery strategy a government response statement will be published which summarizes the actions that the Government of Ontario intends to take in response to the strategy. The implementation of recovery strategies depends on the continued cooperation and actions of government agencies, individuals, communities, land users, and conservationists.

For more information

To learn more about species at risk recovery in Ontario, please visit the Ministry of the Environment, Conservation and Parks Species at Risk webpage.

Recommended citation

Ministry of the Environment, Conservation and Parks. 2019. Recovery Strategy for the Butler’s Gartersnake (Thamnophis butleri) in Ontario. Ontario Recovery Strategy Series. Prepared by the Ministry of the Environment, Conservation and Parks, Peterborough, Ontario. iv + 6 pp. + Appendix. Adoption of the Recovery Strategy for the Butler’s Gartersnake (Thamnophis butleri) in Canada (Environment Canada 2018).

ISBN 978-1-4868-3506-5 (HTML)
ISBN 978-1-4868-3507-2 (PDF)

Content (excluding illustrations) may be used without permission with appropriate credit to the source, except where use of an image or other item is prohibited in the content use statement of the adopted federal recovery strategy.

Cette publication hautement spécialisée « Recovery strategies prepared under the Endangered Species Act, 2007 », n’est disponible qu’en anglais en vertu du Règlement 411/97 qui en exempte l’application de la Loi sur les services en français. Pour obtenir de l’aide en français, veuillez communiquer avec recovery.planning@ontario.ca.

Declaration

The recovery strategy for the Butler’s Gartersnake (Thamnophis butleri) was developed in accordance with the requirements of the Endangered Species Act, 2007 (ESA). This recovery strategy has been prepared as advice to the Government of Ontario, other responsible jurisdictions and the many different constituencies that may be involved in recovering the species.

The recovery strategy does not necessarily represent the views of all of the individuals who provided advice or contributed to its preparation, or the official positions of the organizations with which the individuals are associated.

The recommended goals, objectives and recovery approaches identified in the strategy are based on the best available knowledge and are subject to revision as new information becomes available. Implementation of this strategy is subject to appropriations, priorities and budgetary constraints of the participating jurisdictions and organizations.

Success in the recovery of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy.

Responsible jurisdictions

Ministry of the Environment, Conservation and Parks
Environment and Climate Change Canada – Canadian Wildlife Service, Ontario

Executive summary

The Endangered Species Act, 2007 (ESA) requires the Minister of the Environment, Conservation and Parks to ensure recovery strategies are prepared for all species listed as endangered or threatened on the Species at Risk in Ontario (SARO) List. Under the ESA, a recovery strategy may incorporate all or part of an existing plan that relates to the species.

Butler's Gartersnake (Thamnophis butleri) is listed as endangered on the SARO List. The species is also listed as endangered under the federal Species at Risk Act (SARA). Environment and Climate Change Canada prepared the Recovery Strategy for the Butler's Gartersnake (Thamnophis butleri) in Canada in 2018 to meet its requirements under the SARA. This recovery strategy is hereby adopted under the ESA. With the additions indicated below, the enclosed strategy meets all of the content requirements outlined in the ESA.

This addendum includes updated information about snake fungal disease (SFD) in Ontario and the potential risk that it poses to Butler’s Gartersnake. The Canadian Wildlife Health Cooperative (CWHC), in collaboration with multiple partners, has been conducting surveillance for SFD in Ontario, and this work has demonstrated that the fungus that causes SFD is now relatively widespread in southern Ontario. In 2017, the CWHC published the “Snake Fungal Disease in Canada Rapid Threat Assessment”. The threat assessment concluded that while there is still considerable uncertainty about how SFD will affect Canada’s snake populations, it presents a potentially serious threat, particularly for species at risk.

The Critical Habitat section of the federal recovery strategy provides an identification of critical habitat (as defined under the SARA). Identification of critical habitat is not a component of a recovery strategy prepared under the ESA. However, it is recommended that the approach used to identify critical habitat in the federal recovery, along with any new scientific information pertaining to Butler’s Gartersnake and the areas it occupies, be considered when developing a habitat regulation under the ESA.

1.0 Adoption of federal recovery strategy

The Endangered Species Act, 2007 (ESA) requires the Minister of the Environment, Conservation and Parks to ensure recovery strategies are prepared for all species listed as endangered or threatened on the Species at Risk in Ontario (SARO) List. Under the ESA, a recovery strategy may incorporate all or part of an existing plan that relates to the species.

Butler’s Gartersnake (Thamnophis butleri) is listed as endangered on the SARO List. The species is also listed as endangered under the federal Species at Risk Act (SARA). Environment and Climate Change Canada prepared the Recovery Strategy for the Butler’s Gartersnake (Thamnophis butleri) in Canada in 2018 to meet its requirements under the SARA. This recovery strategy is hereby adopted under the ESA. With the additions indicated below, the enclosed strategy meets all of the content requirements outlined in the ESA.

1.1 Species assessment and classification

The following list is assessment and classification information for the Butler’s Gartersnake (Thamnophis butleri). Note: The glossary provides definitions for abbreviations and technical terms in this document.

• SARO List Classification: Endangered
• SARO List History: Endangered (2011), Threatened (2004)
• COSEWIC Assessment History: Endangered (2010), Threatened (2001), Special Concern (1999)
• SARA Schedule 1: Endangered
• Conservation Status Rankings: G-rank: G4; N-rank: N2; S-rank: S2

1.2 Threats to survival and recovery

Snake Fungal Disease

Ongoing surveillance and monitoring has demonstrated that the fungus that causes snake fungal disease (SFD), Ophidiomyces ophiodiicola, is more widespread in southern Ontario than it was previously thought to be. The disease has been confirmed in Eastern Foxsnakes (Pantherophis gloydi) and Queensnakes (Regina septemvittata), and the fungus has been identified in three additional species from multiple locations across southern Ontario (CWHC 2017). In 2017, the Canadian Wildlife Health Cooperative (CWHC) published the “Snake Fungal Disease in Canada Rapid Threat Assessment” (CWHC 2017), which provides updated information about the distribution and prevalence of SFD in Canada, the risk that SFD poses to Canadian snake populations, and potential management approaches. The threat assessment concluded that there is considerable uncertainty about how SFD will affect Canada’s snake populations, but that it should be considered a serious additive stressor for snake populations, particularly for species at risk. Despite the widespread distribution of the fungus in southern Ontario, incidence of severe epidemics appear to be rare at this time (CWHC 2017). The threat assessment suggests that severe or lethal effects may be largely limited to populations that are already suffering from multiple stressors, such as habitat degradation and fragmentation. Although SFD has not yet been confirmed in Butler’s Gartersnake in Ontario, the fungus is now known to occur within the Ontario range of this species, and at least one individual has been observed with clinical signs that are consistent with SFD (CWHC 2017, S. Marks, pers. comm., 2015). Further to this, Butler’s Gartersnake – like most endangered species – are heavily impacted by multiple stressors, which may make populations particularly susceptible to SFD outbreaks.

1.3 Recovery actions completed or underway

The CWHC, in collaboration with the Ministry of Natural Resources and Forestry and several other organizations and individuals, has been conducting surveillance for Ophidiomyces ophiodiicola in snake populations in Canada. This work has provided valuable new information about the distribution and prevalence of this pathogen in the province. As noted above, the CWHC also conducted a threat assessment of SFD in Ontario (Snake Fungal Disease in Canada Rapid Threat Assessment; CWHC 2017), which provides updated information about the distribution of SFD in Ontario, as well as management recommendations, and will further inform monitoring, research and conservation efforts related to this emerging threat in Ontario.

1.4 Area for consideration in developing a habitat regulation

Under the ESA, a recovery strategy must include a recommendation to the Minister of the Environment, Conservation and Parks on the area that should be considered in developing a habitat regulation. A habitat regulation is a legal instrument that prescribes an area that will be protected as the habitat of the species. The recommendation provided below will be one of many sources considered by the Minister, including information that may become newly available following completion of the recovery strategy, when developing the habitat regulation for this species.

The Critical Habitat section of the federal recovery strategy provides an identification of critical habitat (as defined under the SARA). Identification of critical habitat is not a component of a recovery strategy prepared under the ESA. However, it is recommended that the approach used to identify critical habitat in the federal recovery strategy, along with any new scientific information pertaining to Butler’s Gartersnake (Thamnophis butleri) and the areas it occupies, be considered when developing a habitat regulation under the ESA.

Glossary

Committee on the Status of Endangered Wildlife in Canada (COSEWIC)

The committee established under section 14 of the Species at Risk Act that is responsible for assessing and classifying species at risk in Canada.

Committee on the Status of Species at Risk in Ontario (COSSARO)

The committee established under section 3 of the Endangered Species Act, 2007 that is responsible for assessing and classifying species at risk in Ontario.

Conservation status rank

A rank assigned to a species or ecological community that conveys its degree of rarity at the global (G), national (N) or subnational (S) level. These ranks, termed G-rank, N-rank and S-rank, are not legal designations. Global and National ranks are determined by NatureServe. Subnational S-ranks are determined for Ontario by the Natural Heritage Information Centre. The conservation status of a species or ecosystem is ranked from 1 to 5, preceded by the letter G, N or S which shows the geographic scale of the assessment. The numbers mean the following:

1 = critically imperilled
2 = imperilled
3 = vulnerable
4 = apparently secure
5 = secure
NR = not yet ranked

Endangered Species Act, 2007 (ESA)

The provincial legislation that provides protection to species at risk in Ontario.

Species at Risk Act (SARA)

The federal legislation that provides protection to species at risk in Canada. This act establishes Schedule 1 as the legal list of wildlife species at risk. Schedules 2 and 3 contain lists of species that at the time the Act came into force needed to be reassessed. After species on Schedule 2 and 3 are reassessed and found to be at risk, they undergo the SARA listing process to be included in Schedule 1.

Species at Risk in Ontario (SARO) List

The regulation made under section 7 of the Endangered Species Act, 2007 that provides the official status classification of species at risk in Ontario. This list was first published in 2004 as a policy and became a regulation in 2008.

List of abbreviations

COSEWIC

Committee on the Status of Endangered Wildlife in Canada

COSSARO

Committee on the Status of Species at Risk in Ontario

CWHC

Canadian Wildlife Health Cooperative

ESA

Ontario’s Endangered Species Act, 2007

ISBN

International Standard Book Number

SARA

Canada’s Species at Risk Act

SARO List

Species at Risk in Ontario List

SFD

Snake Fungal Disease

References

Canadian Wildlife Health Cooperative (CWHC). 2017. Snake Fungal Disease in Canada Rapid Threat Assessment. Available at: Canadian Wildlife Health Cooperative Website: Technical Reports

Personal communications

Marks, Steve. 2015. Email correspondence to J. Crowley. Species at risk snake biologist, AMEC Foster Wheeler, Windsor, Ontario.

Appendix 1. Recovery strategy for the Butler’s Gartersnake (Thamnophis butleri) in Canada

Butler’s Gartersnake (Thamnophis butleri): recovery strategy 2018

Official title: Recovery Strategy for the Butler’s Gartersnake (Thamnophis butleri) in Canada 2018

Species at Risk Act

Recovery strategy series

Document information

Recommended citation:

Environment and Climate Change Canada. 2018. Recovery Strategy for the Butler’s Gartersnake (Thamnophis butleri) in Canada. Species at Risk Act Recovery Strategy Series. Environment and Climate Change Canada, Ottawa. viii + 51 pp.

For copies of the recovery strategy, or for additional information on species at risk, including the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) Status Reports, residence descriptions, action plans, and other related recovery documents, please visit the Species at Risk (SAR) Public Registry^{footnote 1[1]}.

Également disponible en français sous le titre « Programme de rétablissement de la couleuvre à petite tête (Thamnophis butleri) au Canada »

© Her Majesty the Queen in Right of Canada, represented by the Minister of Environment and Climate Change, 2018. All rights reserved.

ISBN 978-0-660-25756-3
Catalogue no. En3-4/287-2018E-PDF

Content (excluding the illustrations) may be used without permission, with appropriate credit to the source.

Preface

The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996)^{footnote 2[2]} agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA) the federal competent ministers are responsible for the preparation of recovery strategies for listed Extirpated, Endangered, and Threatened species and are required to report on progress within five years.

The Minister of Environment and Climate Change is the competent minister under SARA for the Butler’s Gartersnake and has prepared this recovery strategy, as per section 37 of SARA. To the extent possible, it has been prepared in cooperation with the Province of Ontario as per section 39(1) of SARA.

Success in the recovery of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy and will not be achieved by Environment and Climate Change Canada, or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this strategy for the benefit of Butler’s Gartersnake and Canadian society as a whole.

This recovery strategy will be followed by one or more action plans that will provide information on recovery measures to be taken by Environment and Climate Change Canada and the Parks Canada Agency and other jurisdictions and/or organizations involved in the conservation of the species. Implementation of this strategy is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.

The recovery strategy sets the strategic direction to arrest or reverse the decline of the species, including identification of critical habitat to the extent possible. It provides all Canadians with information to help take action on species conservation. When critical habitat is identified, either in a recovery strategy or an action plan, SARA requires that critical habitat then be protected.

In the case of critical habitat identified for terrestrial species including migratory birds SARA requires that critical habitat identified in a federally protected area^{footnote 3[3]} be described in the Canada Gazette within 90 days after the recovery strategy or action plan that identified the critical habitat is included in the public registry. A prohibition against destruction of critical habitat under ss. 58(1) will apply 90 days after the description of the critical habitat is published in the Canada Gazette.

For critical habitat located on other federal lands, the competent minister must either make a statement on existing legal protection or make an order so that the prohibition against destruction of critical habitat applies.

If the critical habitat for a migratory bird is not within a federal protected area and is not on federal land, within the exclusive economic zone or on the continental shelf of Canada, the prohibition against destruction can only apply to those portions of the critical habitat that are habitat to which the Migratory Birds Convention Act, 1994 applies as per SARA ss. 58(5.1) and ss. 58(5.2).

For any part of critical habitat located on non-federal lands, if the competent minister forms the opinion that any portion of critical habitat is not protected by provisions in or measures under SARA or other Acts of Parliament, or the laws of the province or territory, SARA requires that the Minister recommend that the Governor in Council make an order to prohibit destruction of critical habitat. The discretion to protect critical habitat on non-federal lands that is not otherwise protected rests with the Governor in Council.

Acknowledgments

Jennifer Brownlee developed the first draft of the Butler’s Gartersnake recovery strategy under contract to Environment and Climate Change Canada, Canadian Wildlife Service – Ontario (EC, CWS-ON). The draft strategy was updated by Rebecca Carter under contract to EC, CWS-ON. Ken Tuininga led the completion of this recovery strategy with assistance from Lauren Strybos, Krista Holmes, Christina Rohe, Marie-Claude Archambault, Angela Darwin and Graham Bryan, (EC, CWS-ON) and Kari Van Allen, Megan Eplett and Madeline Austen (formerly EC, CWS-ON). Contributions from Lesley Dunn (EC, CWS-ON) are also gratefully acknowledged. Al Sandilands (Gray Owl Environmental Inc.), Daniel Noble (Macquarie University), Frederick Schueler (Bishop Mills Natural History Centre), and Jonathan Choquette (SCC Ecological) provided comments and advice during the development of this document. Joe Crowley, Jay Fitzsimmons, Leanne Jennings, Aileen Wheeldon, (Ontario Ministry of Natural Resources and Forestry (OMNRF) and Mike Oldham (Natural Heritage Information Centre, OMNRF) reviewed and provided comments and advice during the development of this document. Megan Hazell (AMEC Foster Wheeler), Wayne King (LGL Ltd.) and Barbara Macdonnell (Ministry of Transportation Ontario) also reviewed and provided comments during the development of the document and were extremely helpful in sharing data based on the extensive monitoring work completed for the requirements of the Endangered Species Act, 2007 permits for the development of the Right Honourable Herb Gray Parkway.

Acknowledgment and thanks are given to all other parties that provided advice and input used to help inform the development of this recovery strategy including various Indigenous organizations and individual citizens, and stakeholders who provided input and/or participated in consultation meetings.

Executive Summary

Butler’s Gartersnake is listed as Endangered^{footnote 4[4]} on Schedule 1 of the federal Species at Risk Act. The species is listed as Endangered in Ontario under the provincial Endangered Species Act, 2007 (ESA 2007). Butler’s Gartersnake (Thamnophis butleri) is a small gartersnake with three distinct yellow to orange longitudinal stripes running from head to tail over a brown body. A dark checkered pattern is evident running alongside its stripes. Like most other small Canadian snakes, this species has not been well studied. Butler’s Gartersnake is often confused with two other gartersnakes coexisting in its range, both belonging to the same genus, Thamnophis. These similar species are the Common Gartersnake (T. sirtalis) and the Eastern Ribbonsnake (T. sauritus). Butler’s Gartersnake is shorter in total length (38 – 51 cm), more docile and has a unique pattern and position of side stripes in comparison to these species.

In Canada, Butler’s Gartersnake is restricted to Ontario where it has recently been found in two regions: Windsor-Sarnia (Essex, Chatham-Kent, Lambton Counties and Walpole Island) and Luther Marsh (Dufferin and Wellington Counties). Further surveys are required to determine if it still exists in other areas including: Skunk’s Misery (Lambton and Middlesex Counties), Parkhill (Middlesex County) and additional locations in the Windsor-Sarnia region. In the United States, Butler’s Gartersnake is restricted to the Great Lakes Region and is found within four states: Wisconsin, Ohio, Indiana, and Michigan.

Butler’s Gartersnake is found in grasslands, old fields, disturbed sites, urban and industrial sites and tallgrass prairie where a dense cover of grasses or herbs and a heavy thatch layer are present. The species is often found in close proximity to wet areas such as small marshes (seasonally dry), swales, and small bodies of water located in vacant urban lots (industrial lands), parks and tallgrass prairie remnants. It is possible that the Butler’s Gartersnake may have been a species of wetter habitats and may have started to utilize drier areas following the introduction of earthworms to Ontario.

The major threats contributing to Butler’s Gartersnake decline are ongoing habitat loss, degradation and fragmentation, due to urban, industrial and road development as well as agricultural expansion.

There are unknowns regarding the feasibility of recovery of the Butler’s Gartersnake. The population and distribution objective for Butler’s Gartersnake is to maintain the current abundance and distribution of all extant subpopulations. Where biologically and technically feasible, the distribution and abundance of extant subpopulations should be increased and habitat connectivity between local subpopulations improved. The broad strategies to be taken to address the threats to the survival and recovery of Butler’s Gartersnake are presented in the section on Strategic Direction for Recovery (Section 6.2).

There are several locations that may still support Butler’s Gartersnake, however these locations have not been surveyed recently or adequately and/or there is a lack of certainty in the data needed to identify critical habitat. For this reason, critical habitat for Butler’s Gartersnake has only been partially identified in this recovery strategy. Critical habitat is identified for 27 extant locations in Ontario and occurs within the geographic regions of Windsor, Sarnia and Luther Marsh. The Schedule of Studies (Section 7.2) outlines the activities required to identify additional critical habitat necessary to support the population and distribution objectives for this species.

One or more action plans for Butler’s Gartersnake will be completed by December 2025.

Recovery feasibility summary

Based on the following four criteria that Environment and Climate Change Canada uses to establish recovery feasibility, there are unknowns regarding the feasibility of recovery of the Butler’s Gartersnake. In keeping with the precautionary principle, this recovery strategy has been prepared as per section 41(1) of SARA, as would be done when recovery is determined to be technically and biologically feasible. This recovery strategy addresses the unknowns surrounding the feasibility of recovery.

1. Individuals of the wildlife species that are capable of reproduction are available now or in the foreseeable future to sustain the population or improve its abundance.

Yes. There are currently 27 to 38 extant^{footnote 5[5]} locations^{footnote 6[6]} of Butler’s Gartersnake in Canada, which occur within four geographic regions. The species is frequently locally abundant where it does occur and may be the most common snake species at some locations. Most local subpopulations are small, though exact numbers may not be known, and may be threatened by negative genetic effects of small population size and demographic stochasticity as well as numerous other threats (COSEWIC 2010). However, there are several large subpopulations of this species in Ontario that are capable of maintaining the species in the province (COSEWIC 2010).

2. Sufficient suitable habitat is available to support the species or could be made available through habitat management or restoration.

Unknown. In Ontario, it is not known if sufficient suitable habitat is available to support the current population. Walpole Island contains one of the largest remnant tracts of native prairie in Ontario but the size of its Butler’s Gartersnake population is not known. This species is also found within Nature Reserves and Conservation Areas in Ontario such as Ojibway Prairie (Windsor) and Luther Marsh (north of Guelph) and it may also still exist in Skunk’s Misery, Parkhill and in additional locations in the Windsor-Sarnia region (see Figure 2). It is also possible that in some urban areas, new habitat may be created as abandoned industrial sites are allowed to naturalize (COSEWIC 2010). However, its distribution, particularly for some urban subpopulations, is limited due to habitat fragmentation and confined to a limited area of Southern Ontario. This results in subpopulations being isolated from one another, which can lead to a reduction in genetic diversity and even inbreeding. Thus, maintaining connectivity between subpopulations is crucial to the recovery of Butler’s Gartersnake.

3. The primary threats to the species or its habitat (including threats outside Canada) can be avoided or mitigated.

Unknown. The primary threats to the species are urban, industrial and road development as well as agricultural expansion. Some current and future development and agricultural expansion in suitable Butler’s Gartersnake habitat can be avoided through stewardship, co-operation with landowners, land managers and First Nations, land use management practices and policy and regulations such as the recently implemented activities for the Right Honourable Herb Gray Parkway. Snake barriers, monitoring coverboards, inspecting key habitat features and working within timing windows have reduced impacts to snakes during construction (AMEC Environment and Infrastructure, environmental consultants on behalf of the Parkway Infrastructure Constructors and Windsor Essex Mobility Group 2013). However, many local subpopulations exist in small and or isolated habitat fragments, in urban areas with established road networks where mitigation may be difficult or impossible.

4. Recovery techniques exist to achieve the population and distribution objectives or can be expected to be developed within a reasonable timeframe.

Yes. Standard techniques exist for Butler’s Gartersnake monitoring and habitat restoration, including habitat enhancement and the creation of hibernacula. Land management practices have also been developed to provide stewardship information to agricultural, urban and industrial private land owners. These include best management practices such as implementing and maintaining wildlife corridors, controlling invasive species such as European Common Reed (Phragmites australis australis), maintaining open-canopy, dense ground-layer vegetation and avoiding activities that allow the encroachment of woody vegetation (Tallgrass Ontario 2005; Savanta Inc. 2008; Ontario Ministry of Natural Resources 2011; Mifsud 2014; Wisconsin Department of Natural Resources 2014). Research on many recovery techniques specific to Butler’s Gartersnake was also carried out to fulfill the Endangered Species Act, 2007 permit requirements for the development of the Right Honourable Herb Gray Parkway. This included research that involves monitoring of Butler’s Gartersnake use of eco-passages and road culverts.

1. COSEWIC^{footnote *[*]} species assessment information

Date of Assessment: November 2010

Common Name: Butler's Gartersnake

Scientific Name: Thamnophis butleri

COSEWIC Status: Endangered

Reason for Designation: Most populations of this species occur in small, scattered habitat remnants. Most are isolated so they are threatened by the negative genetic effects of small population size and by demographic stochasticity^{footnote **[**]}. Recent surveys have not detected the species at several sites where they were formerly known. Road mortality, ongoing habitat loss and fragmentation are also threats to this small specialized snake.

Canadian Occurrence: Ontario

COSEWIC Status History: Designated Special Concern in April 1999. Status re-examined and designated Threatened in November 2001. Status re-examined and designated Endangered in November 2010.

2. Species status information

The global conservation rank for Butler’s Gartersnake (Thamnophis butleri) is Apparently Secure^{footnote 7[7]} (G4) (NatureServe 2017). In the United States, it is ranked nationally as Apparently Secure (N4), and subnationally as Critically Imperiled^{footnote 8[8]} in Indiana (S1), Vulnerable^{footnote 9[9]}/Apparently Secure in Wisconsin (S3S4), Apparently Secure in Michigan (S4), and has not been officially ranked in the state of Ohio (SNR). In Canada, Butler’s Gartersnake is ranked Imperiled both nationally (N2) and provincially (S2) in Ontario (NatureServe 2017).

Butler’s Gartersnake is currently listed as Endangered^{footnote 10[10]} on Schedule 1 of the federal Species at Risk Act (SARA) and is listed as Endangered under Ontario’s Endangered Species Act, 2007 (ESA 2007). Approximately 16% of the global range occurs in Canada (COSEWIC 2010).

3. Species information

3.1 Species description

Butler’s Gartersnake is a small snake typically ranging from 38 to 51 cm in length with a maximum recorded length of 73.7 cm (Minton 1972 as cited in Rossman et al. 1996). It has a small head only slightly broader than the neck (Rossman et al. 1996) and a tail that is generally 20 to 25% of its total length (Sandilands 2001). Bearing the characteristic striped pattern of gartersnakes, Butler’s Gartersnake has three longitudinal yellow to orange stripes, one dorsal^{footnote 11[11]} and two lateral^{footnote 12[12]} (Conant and Collins 1991; Rossman et al. 1996; Ernst and Ernst 2003). The dorsal stripe may also be white to cream in colour. The lateral stripes are centred on the 3^rd scale row and at least anteriorly, they extend onto scale rows 2 and 4 (Ernst and Barbour 1989; Ernst and Ernst 2003; COSEWIC 2010). In some regions, the lateral stripes may be centred on the third scale row and only encompass half of the second row. The whitish underbelly is divided from the lateral stripe by a broad chestnut coloured stripe along the first lateral scale row and the upper edges of the ventral^{footnote 13[13]} scales (COSEWIC 2010). The back may range from olive-brown or chestnut to black.

Butler’s Gartersnake may be confused with two other Thamnophis species occurring in Ontario, the Common Gartersnake (T. sirtalis) and the Eastern Ribbonsnake (T. sauritus) which both occur in southwestern Ontario (Sandilands 2001; COSEWIC 2010). In the case of the Eastern Ribbonsnake, the lateral stripes are on rows 3 and 4, while for the Common Gartersnake they are on rows 2 and 3. The Common Gartersnake and Eastern Ribbonsnake have larger heads and more pronounced necks than the Butler's Gartersnake. The Eastern Ribbonsnake also has a distinct white crescent in front of the eye, is more slender and has a longer tail. Further, the Eastern Ribbonsnake does not occur in most of the areas in southwestern Ontario where Butler’s Gartersnakes are found (Ontario Nature 2014).

Like many other snake species, Butler’s Gartersnake avoids mid-day sun and becomes active in the morning and evening during midsummer (Logier 1939; Catling and Freedman 1980(a); Ernst and Ernst 2003). Butler’s Gartersnakes are non-aggressive, and will quickly seek shelter in thick grass thatch if disturbed (Ernst and Barbour 1989; Ernst and Ernst 2003; COSEWIC 2010). Although Butler’s Gartersnake can move quickly in grassy areas, when travelling over hard surfaces it moves much more slowly having to slither sideways, in a “side-winding” motion (Sandilands 2001; Ontario Nature 2011). Butler’s Gartersnake also has a prehensile^{footnote 14[14]} tail allowing it to wrap around vegetation or other objects to avoid predation (Environment Canada 2014).

3.2 Species population and distribution

Butler’s Gartersnake is endemic to North America where its range is considered one of the most restricted of all snake species (Sandilands 2001); its range is limited to an area near the lower Great Lakes in the United States (south-eastern Wisconsin, Indiana, Ohio and the Lower Peninsula of Michigan) and Canada (southern Ontario) (Nature Serve 2013) (Figure 1). The global range is estimated to be between 20,000 and 200,000 km² (Nature Serve 2013). Even though Butler’s Gartersnake subpopulations are somewhat disjunctive^{footnote 15[15]} within their range, in many cases this species is locally abundant (Conant 1951; Conant and Collins 1991; Rossman et al. 1996). The species’ current disjunct distribution and affiliation with prairie and grassland habitat has been cited as support for the idea that the Butler’s Gartersnake’s current Canadian range is composed of remnant prairie patches that once formed a larger continuous prairie corridor occupied by the species (COSEWIC 2010).

The current Canadian range of Butler’s Gartersnake is restricted to four geographically isolated regions in southwestern Ontario. Two regions: Windsor-Sarnia (Essex, Chatham-Kent, and Lambton Counties) and Luther Marsh (Dufferin and Wellington Counties) contain recent occurrence observations of Butler’s Gartersnake. The species is also historically known to occur in Skunk’s Misery (Lambton and Middlesex Counties) and Parkhill (Middlesex County) (COSEWIC 2010), however, further surveys are needed to confirm the species’ presence in these two areas. The species is considered extirpated from a fifth region near Rondeau Provincial Park.

Within these regions, 48 locations of Butler’s Gartersnake have been documented (Figure 2, Appendix B). For the purposes of this report, the term ‘location’ is used synonymously with the term ‘subpopulation’. Six are considered extirpated^{footnote 16[16]} and four are considered historical (i.e., not observed in >20 years). The number of extant subpopulations is believed to be between 27 and 38. The uncertainty in the number of extant subpopulations is due to the fact that at seven locations, which were last visited in 2009 (including Walpole Island), surveyors did not find any Butler’s Gartersnakes, although suitable habitat appears to be available. An additional three locations have lost significant portions of their habitat (COSEWIC 2010, Appendix B: locations 11, 14, 40) and additional surveys are required to confirm the status at these locations.

Seven locations visited in 2009 are new locations not previously noted in the literature. New locations have not been assessed by the Natural Heritage Information Centre and in the future, the enumeration of subpopulations may better align with element occurrence information. More recently, Noble et al. (2013) suggested that Butler’s Gartersnakes in Windsor, Sarnia, and Luther Marsh consist of four to five genetically distinct clusters which are subdivided into three or four subpopulations but it is not clear how the known locations are distributed within those clusters.

Throughout its current distribution, Butler’s Gartersnakes are mainly scattered in small, fragmented locations. No snakes have been encountered at Skunk’s Misery since the late 1980’s despite several targeted searches. Only one snake is known from Parkhill (1992), and this area was not searched in 2009 when other surveys for Butler’s Gartersnake were conducted in Ontario (COSEWIC 2010). Further surveying, particularly in the spring, is required to confirm the presence/absence of the species at Skunk’s Misery, Parkhill, Walpole Island and an additional 12 locations within the Windsor-Sarnia geographic region (COSEWIC 2010; J. Choquette pers. comm. 2014).

Several effective methods for detecting this secretive species enabled reliable estimates for a few Windsor subpopulations during the Herb Gray Parkway (HGP) project.^{footnote 17[17]} Radio telemetry using specialized transmitters, passive integrated transponder (PIT) tagging, a mark-recapture program and hibernacula enclosure fences to confirm hibernacula locations and snake use were employed. Through modeling of data collected using these methods, this project produced an estimate of around 550 individuals for HGP monitored areas in 2013 (LGL 2010; AMEC Environment and Infrastructure, environmental consultants on behalf of the Parkway Infrastructure Constructors and Windsor Essex Mobility Group (AMEC) 2012, 2013, 2014).

Currently, the long term survival of Butler’s Gartersnake in Ontario is uncertain. In 2010 Butler’s Gartersnake was reassessed from Threatened to Endangered by COSEWIC due to its small overall distribution in Canada, ongoing habitat loss including fragmentation and proposed development at many locations, and the decline and downward trend in the number of known local subpopulations. Most local subpopulations exist in small and or isolated habitat fragments and may be threatened by negative genetic effects of small population size and demographic stochasticity (COSEWIC 2010).

3.3 Needs of the Butler's Gartersnake

Butler’s Gartersnake is thought to be originally associated with post-glacial prairie in the Great Lakes region over 7,000 years ago (Schmidt 1938; Smith 1957; Bleakney 1958; Environment Canada 2014) though it is possible that it may have been a species of wetter habitat, beginning to use drier areas only after earthworms were introduced to Ontario (Schueler pers. comm. 2016). This species has persisted in prairie remnants dominated by grasses including Big Bluestem (Andropogon gerardii) and Little Bluestem (Schizachyrium. scoparium) in southwestern Ontario (Sandilands 2001), though many populations now persist in highly altered human landscapes (e.g., fields, parklands, etc.). COSEWIC (2010) also indicates that all Butler’s Gartersnake locations (with the exception of Luther Marsh) coincide with remnants of tallgrass prairie and oak savanna habitats which are critically imperiled in Ontario. Only 2.4 percent of northern tallgrass prairie remains in all of North America today (Samson et al. 2004), with less than 1 percent remaining in Ontario (Bakowsky and Riley 1994; Catling and Brownell 1999; Catling 2008).

General habitat needs

Butler’s Gartersnake habitat in Ontario is characterized by open areas with dense grasses (e.g., cultural meadows, grasslands, old fields, tallgrass prairie communities) in close proximity to wet areas (i.e., small marshes, seasonal wet areas, small bodies of water) (Logier 1939; Planck and Planck 1977; Conant and Collins 1991; COSEWIC 2010). Dense grass cover with a heavy thatch layer is essential to its habitat, as the thatch layer allows Butler's Gartersnakes to move around in search of food under cover from predators (Planck and Planck 1977). In some areas, the species persists in early successional habitat where open grasslands are supporting shrubs and trees (Logier 1939). Butler’s Gartersnake is also known to occur along treed edges and in vacant lots, small parks and abandoned sites in urban areas (Ernst and Barbour 1989; Rossman et al. 1996; Ernst and Ernst 2003; AMEC 2014).

Live birthing habitat

Core use areas of Butler’s Gartersnake are typically associated with live birthing habitat or open basking habitat where females spend large amounts of time prior to giving birth (AMEC 2012; 2013). Butler’s Gartersnakes are ovoviviparous (give birth to live young rather than lay eggs) and have between 4 and 20 young by early July to mid-September (Vogt 1981; Ernst and Ernst 2003; LGL and URS 2010). During the first two weeks of July, gravid^{footnote 18[18]} females may suddenly change behaviour and move out of previous activity areas in rapid linear movements to live birthing sites (LGL 2011; AMEC 2012, 2013, 2014); sometimes travelling over 200 m outside their activity areas (LGL 2010). Others were documented, also in multiple years, basking in habitats adjacent to live birthing sites just prior to giving birth (AMEC 2012, 2013, 2014). Live birthing habitat for Butler’s Gartersnake consists of lowland areas or wet depressions surrounded by higher and drier land. Drier areas typically include shrub or tree cover along the edges of wet depressions, and may include wetland indicator plant species typically found in swamps and marshes (LGL 2011; AMEC 2012, 2013, 2014).AMEC (2012, 2013, 2014) confirmed fidelity to live birthing areas across successive years and in multiple monitoring zones, as part of the HGP monitoring, where the same live birthing areas were used by the same Butler’s Gartersnake population.

Hibernation habitat

Butler’s Gartersnakes commonly hibernate individually through the cold winter months across their range, beginning hibernation in mid-September and not emerging until early April (Conant 1951; Wright and Wright 1957; LGL 2010). Hibernacula^{footnote 19[19]} recorded in Ontario include: Devil Crayfish (Cambarus diogenes; also known as Chimney Crayfish or Meadow Crayfish) burrows, small mammal burrows, drains, log piles, and other underground sites (LGL 2010; AMEC 2012, 2013, 2014). Radio-tracked Butler’s Gartersnakes largely used crayfish burrows, often trying several burrows in the fall before settling on one for the winter (AMEC 2012, 2013, 2014). Hibernacula are usually associated with wetland habitats (open areas or more treed areas) or open water (drainage ditches), as both Chimney and Meadow Crayfish require certain water levels in areas where they create their burrows (i.e., must be able to reach ground water during periods of drought) (Bovbjerg, 1952; Hobbs 1989). To date, Butler’s Gartersnakes have not yet been observed using the artificial hibernacula created to mitigate impacts to individuals captured during construction of the HGP (AMEC 2013); though several relocated Butler’s Gartersnakes have found new hibernacula in the habitats to which they were moved, suggesting that adaptation to new habitats is possible for some individuals. The Wisconsin Department of Natural Resources (WDNR) identified several man-made structures as providing hibernacula for Butler’s Gartersnake, such as old building foundations, sink holes, and improperly capped landfills and dumps (Freedman and Catling 1978; WDNR 2005; WDNR 2014).

Foraging habitat

Butler’s Gartersnakes spend most of their time during active months, generally April to September, foraging in long grasses found in tallgrass prairie, cultural thickets, cultural meadows, and meadow marshes (Planck and Planck 1977; LGL 2010; AMEC 2012). The species’ preference for open grassland habitat with access to wetter areas may be related to its preferred prey, earthworms (Catling and Freedman 1980(a); Lyman Henley and Burghardt 1995; W. King pers. comm. 2014). However, prior to the introduction of earthworms to Ontario, Butler’s Gartersnake may have been a species of wetter habitats (Schueler pers. comm. 2016).

Thermoregulation/mating habitat

Butler’s Gartersnakes regulate their body temperature by basking and cooling throughout the day (Huey and Kingsolver 1989; Grant 1990). In order to elevate their body temperature, Butler’s Gartersnakes seek out open spaces in vegetation, edges of water, the top of logs, coverboards, grass thickets, brushpiles and clusters of vegetation up to a metre above the ground (LGL 2010; AMEC 2013). The species has also been observed basking on gravel roads on cool evenings (C. Campbell and F.W. Schueler pers. comm. 2009) and along walking/bicycle trails (S. Gillingwater pers. comm. 2010). Planck and Planck (1977) observed snakes basking on top of shingles and crawling underneath to forage for earthworms. Mating often takes place at basking areas in close proximity to their hibernation sites, thus suitable habitat during this life process consists of many of the above habitat types from open spaces in vegetation to grass thickets (Harding 1997; Holman et al. 1999). In addition to basking sites, cooling sites are used by Butler’s Gartersnake to lower body temperature during hot days in mid to late summer (LGL 2011). Cooling sites include shady areas such as the base of mature thickets, dogwood bushes, underground retreat sites, rock piles, large rocks, forest edges and shrubs, and various man-made structures (Logier 1939; LGL 2010; LGL 2011). Locations along the edges of forested areas and cultural thickets are frequently used as cooling sites or cover (LGL 2010), and underground dens may also be used as shelters or dwelling places to avoid extremely hot periods in mid-summer (Logier 1939; Carpenter 1952; Catling and Freedman 1980).

Movement (commuting and dispersal^{footnote 20[20]}) habitat

Butler’s Gartersnake populations have typically shown limited movements and high site fidelity (Carpenter 1952; COSEWIC 2010; LGL 2010; AMEC 2013). In southern Michigan, Carpenter (1952) found Butler’s Gartersnakes had an activity range of two acres (0.8 hectares). In southern Ontario the species’ activity range has been found to be slightly larger at 1.6 hectares (AMEC 2013). Carpenter (1952) found that individual snakes did not extend their movements over the entire available habitat, but limited themselves to a smaller parcel. In mark-recapture studies Butler’s Gartersnakes were frequently recaptured within 50 m of their original capture location and often under the same coverboard (recapture distance of 0 m) (AMEC 2013, 2014). LGL (2010) and AMEC (2013) found that Butler’s Gartersnakes exhibited localized movements within their activity area at certain times of the year (e.g., movements to and from live birthing sites and hibernacula). Recent work by AMEC also showed that range lengths (maximum distance moved in an active season) for non- relocated Butler’s Gartersnakes were between 150 – 380 m (AMEC 2012, 2013, 2014). Movements across roads, through residential/landscaped areas or via linear corridors such as drains were rare, and most individuals kept to the outer boundaries of forested or wooded areas. Relocated individuals exhibited larger ranges, most likely due to exploratory movements after release (AMEC 2013).

Though a clear outlier in comparison to all other recaptured snakes in the study, one snake was recaptured 1,200 m from its initial capture site in Point Edward, Ontario (adjacent to Sarnia) (J. Kamstra pers. comm. 2009). This behaviour may be a response to dry summer conditions and a lack of available food. As temporary wet areas dry up in late spring and early summer, Butler’s Gartersnakes are known to move to portions of their habitat where wet or moist areas remain throughout the year (W. King pers. comm. 2014). Long linear movements of up to 250 m have also been associated with movement from basking sites towards hibernacula in the fall (AMEC 2013; M. Hazell pers. comm. 2014).

3.4 Biological limiting factors

Although some populations may still be relatively large, even within the City of Windsor, many Butler’s Gartersnake subpopulations in Ontario are small and isolated, and the disjunct distribution of this species indicates that it likely occupied a much wider range in the past (COSEWIC 2010). The species may have occurred in wetter habitat historically, and it is possible that it only began to utilize drier areas following the introduction of earthworms to Ontario (i.e. the St. Clair/Detroit River marshes moving to surrounding grassland/prairie areas) (Schueler pers. comm. 2016). Another possibility is that the species’ previous range is believed to have occurred under warmer, drier conditions and may suggest that the species is limited by climate (Grand River Conservation Authority 2004). Regardless, Butler’s Gartersnake has become quite dependent on earthworms as its preferred food source, largely restricting its distribution to grassland habitats associated with wet or moist areas supporting earthworms and possibly limiting its ability to colonize more arid grasslands (Carpenter 1952; Lyman Henley and Burghardt 1995). The tendency of Butler’s Gartersnakes to typically move only short distances suggests that they may not attempt to cross gaps between unsuitable habitats, making them susceptible to habitat fragmentation (COSEWIC 2010).

The small subpopulation sizes of Butler’s Gartersnake in Ontario may limit the ability of the species to adapt to environmental change and, as a result, subpopulations may be subjected to higher extinction risks (Shaffer 1981; Reed et al. 2003; Santos et al. 2009) due to stochastic and human related factors (Santos et al. 2009). Boulding and Hay (2001) indicate that environmental changes can decrease population size, causing genetic variation to decrease. Decreased genetic variation in combination with inbreeding depression, can limit further adaptive responses (Hoffman and Willi 2008). Specific data on inbreeding depression in Butler’s Gartersnake are not available, but studies focused on other snake species (e.g., Madsen et al. 1996) found that inbreeding depression does occur and can cause reduced brood size and a high proportion of unviable offspring. A simulation involving the Wisconsin population of Butler’s Gartersnake found that populations with less than approximately 40-50 adult females begin to show disproportionally higher risk of extirpation (Hyde et al. 2007). Hyde et al. (2007) also indicates that reductions in survival of juveniles through inbreeding depression can have a major impact on Butler’s Gartersnake population viability. That said, other recent studies show that some reptile species are not affected by these genetic issues, suggesting that further work is needed.

4. Threats

4.1. Threat assessment

^aLevel of concern

signifies that managing the threat is of (high, medium or low) concern for the recovery of the species, consistent with the population and distribution objectives. This criterion considers the assessment of all the information in the table.

^bSeverity

reflects the population-level effect (high: very large population-level effect, moderate, low, unknown).

^cCausal certainty

reflects the degree of evidence that is known for the threat (high: available evidence strongly links the threat to stresses on population viability; medium: there is a correlation between the threat and population viability e.g. expert opinion; low: the threat is assumed or plausible).

^d

Threats with a low level of concern are listed and described but may not be specifically addressed in the recovery approaches.

4.2 Description of threats

This section describes major threats outlined in Table 1, emphasizes key points and provides additional information. Although threats are listed individually, an important concern is the long-term cumulative effect of a variety of threats to local Butler’s Gartersnake subpopulations.

It should be noted that most of these threats are typically more harmful during the species’ active season (generally April to September) because they lead to higher levels of direct mortality or mutilation. Moreover, exposure to threats increases in periods in which Butler’s Gartersnake movements increase, for example when some females move greater distances between hibernation and live birthing areas in the spring. Some of these threats could also affect the species during the non-active season, such as those that destroy or alter hibernacula.

Among the mechanisms through which threats can impact Butler’s Gartersnake populations, isolation through habitat loss is of special concern, as it can lead to a breakdown of metapopulation dynamics^{footnote 21[21]} and a reduction in genetic diversity and possibility of rescue effect^{footnote 22[22]}. Threats such as increasing urbanization, agricultural practices, the development of road networks, and the spread of exotic or invasive species can all contribute to further isolation of remaining subpopulations. Most threats including the various types of development can impact the species significantly regardless of the time of year by eliminating habitat. Collection for personal use has also been documented in Ontario (M. Hazell pers. comm. 2014) and subsidized predation and direct persecution are believed to occur. Threats are listed in decreasing order of concern.

Urban and industrial development

Rare habitat types in Southern Ontario such as prairies and grasslands are quickly disappearing due to an increasingly urbanized environment. Urbanization is a widespread threat and has resulted in the documented loss of Butler’s Gartersnake locations in Michigan (T. Cox pers. comm. 2009 as cited in COSEWIC 2010) and Ontario. Research conducted in 2009 within the Windsor-Sarnia region identified eight previously known sites destroyed by development (COSEWIC 2010).

Other threats associated with increasing urban and industrial development include the frequent mowing and management of lawns which can eliminate habitat and make snakes more vulnerable to predation, and the destruction or alteration of natural and man-made structures that are used by Butler’s Gartersnake for thermoregulation or hibernacula (COSEWIC 2010). Additionally, the drainage of wet areas (seasonal wetlands, small marshes, ponds) used by Butler’s Gartersnakes may result from various development projects (Joppa and Temple 2005).

Agricultural practices, expansion and intensification

Dense cover of grasses or herbs and a heavy thatch layer are essential habitat characteristics of Butler’s Gartersnake (Planck and Planck 1977). The prevalence of intensive agricultural practices in southwestern Ontario limits the establishment of Butler’s Gartersnake habitat. Continued disturbances through tilling and ploughing prevent the establishment of grasses and thatch. The expansion of agricultural land might also involve the drainage of seasonal wetlands, small marshes and ponds which are often used by Butler’s Gartersnake. The conversion of snake habitat into arable^{footnote 23[23]} land has been documented (COSEWIC 2010). In the 1980s a location within Essex County, which was known as one of the largest local subpopulations of Butler’s Gartersnake, was destroyed when it was converted to agricultural use (Planck and Planck 1977).

Pesticides and herbicides could negatively affect Butler’s Gartersnake because pesticides easily find their way into soils and can be toxic to earthworms (Pimentel 2005), their main prey item. A study conducted by Potter et al. (1990) found that pesticides can significantly decrease earthworm populations. Casbourn et al. (1976) found a strong relationship between the number of earthworms and density of Butler’s Gartersnake.

Development of roads and highways

An ever-expanding road network across southern Ontario has created a severely fragmented landscape, increasing subpopulation isolation, reducing landscape connectivity, and threatening the survival of this species across its range. Road networks fragmenting continuous tracts of suitable habitat have a significant impact on Butler’s Gartersnakes, which already have a limited home range (Carpenter 1952; Oliver 1955; DRIC 2009; COSEWIC 2010). Butler’s Gartersnakes are particularly susceptible to road mortality (Sandilands 2001) because they are slow-moving in non vegetated areas (Ruthven 1904; Ontario Nature 2011), are small and very difficult for drivers to see on roads, and can be attracted to the open habitat of road corridors for their thermal properties. Although no detailed studies have investigated the effects of road networks on Butler’s Gartersnake, road mortality has been observed across the species’ range (Harding 1997; J. Choquette pers. comm. 2009 as cited in COSEWIC 2010; LGL 2010). One study that did document road mortality in 2010 found multiple Butler's Gartersnakes killed on roads (Choquette 2014), and dispersal of radio-tracked Butler's Gartersnakes appeared to be limited by existing roads.

Altered disturbance regime

With a lack of suitable disturbance, succession back to forested areas poses a threat to the Butler’s Gartersnake as the species relies upon open grassland habitats. This may occur as unused farmland is allowed to succeed into forest, or as a result of fire suppression in grassland/prairie areas. It may be that habitat succession towards mature forest has contributed to the population reduction seen at Skunk’s Misery, as it has reduced the amount of suitable habitat available (COSEWIC 2010).

Exotic and invasive species

Exotic or invasive species have contributed to the loss of suitable habitat for Butler’s Gartersnake (Hyde et al. 2007; Kapfer et al. 2013; Mifsud 2014). Although Butler’s Gartersnakes may readily use small stands or patches of some non-native grass species; large, dense stands of European Common Reed (Phragmites australis australis) and Reed Canary Grass (Phalaris arundinacea) are not preferred, as they can alter habitat structure by shading basking sites and eliminating live birthing areas (Kapfer et al. 2013; W. King pers. comm. 2014).

Subsidized predation

Predation by dogs and domestic and feral cats, as well as raccoons and skunks, may be a significant threat (Loss et al. 2013). This is due to the large human population within the highly urbanized portions of the Butler’s Gartersnake range in Canada, and the fact that Butler’s Gartersnakes will use human-modified habitats. Recent research shows that feral cats are a significant threat to reptile populations in the United States (Loss et al. 2013). Populations of raccoons are dense in southern Ontario (approximately 1.1 million), especially around urban areas where there is an estimated 8 18 raccoons per square kilometre (OMNR 2009).

Direct persecution

Negative attitudes toward snakes are common throughout North America, and even harmless species such as Common Gartersnakes are routinely killed (Gillingwater, pers. obs.) out of fear, prejudice or ignorance (Choquette 2011). Although it is unclear how significant a threat human persecution^{footnote 24[24]} is to the Butler’s Gartersnake, the risk of persecution is generally greater for snake species that inhabit highly urbanized areas where the incidence of snake-human interaction is high (Choquette 2011). Snakes regularly elicit reactions of fear or hostility from the general public, and as a result, discriminate killing can be a significant source of mortality (Ashley et al. 2007).

Collection for personal use

There have been several instances of collection observed in Ontario, presumably for personal use (M. Hazell pers. comm. 2014). While this threat may be of low concern to the species as a whole (COSEWIC 2010), urban snake populations may be at greater risk due to the proximity of large human populations.

Snake Fungal Disease

Another potential threat that may affect the Butler’s Gartersnake is Snake Fungal Disease (SFD) (Ophidiomyces ophiodiicola) (Sleeman 2013). This is an emerging fungal disease in wild snakes that causes severe skin lesions, leading to widespread morbidity and mortality (Sleeman 2013; Allender et al. 2015). SFD is currently known to affect several species including the Northern Watersnake (Nerodia sipedon), Eastern Foxsnake (Pantherophis gloydi), Eastern Milksnake (Lampropeltis triangulum), and Massasauga (Sistrurus catenatus) (Sleeman 2013). SFD has been confirmed in Ontario, in an Eastern Foxsnake found in southwestern Ontario in 2015 (Crowley pers. comm. 2015). It has also been confirmed in nine states in the U.S., although it is considered likely to be even more widespread (Sleeman 2013).

5. Population and distribution objectives

The population and distribution objective for Butler’s Gartersnake is to maintain the current abundance and distribution of all extant subpopulations. Where biologically and technically feasible, the distribution and abundance of extant subpopulations should be increased and habitat connectivity between local subpopulations improved.

The above objective has been set recognizing that the abundance of this species is challenging to determine due to the species’ habits. However, some effective methods for detecting this species have been developed during the Herb Gray Parkway (HGP) project as discussed in section 3.2.

Butler’s Gartersnake has recently been found in only two regions in Ontario: Windsor Sarnia and Luther Marsh. Additional surveys are needed to determine the presence/absence of the species in two others, Skunk’s Misery and Parkhill, as well as nine unknown and four historical locations throughout Windsor-Sarnia, including Walpole Island (COSEWIC 2010; J. Choquette pers. comm. 2014). As many Butler’s Gartersnake populations are disconnected both within the species’ broader range, and within the local subpopulations found in Ontario’s urban areas, such as the habitat in the Windsor-Sarnia region. Some of the urban subpopulations numbers in particular may be below sustainable levels. Because of this, increasing the area occupied by subpopulations, as well as improving habitat connectivity between occupied habitats is vital for the survival of the species. Increasing connectivity will also reduce the likelihood of a genetic bottleneck^{footnote 25[25]} within the species’ Canadian range.

6. Broad strategies and general approaches to meet objectives

6.1 Actions already completed or currently underway

Recovery actions described in the Draft Walpole Island Ecosystem Recovery Strategy (Bowles 2005) included raising awareness in the First Nation community about species at risk, including Butler’s Gartersnake. Pamphlets, calendars, newsletter articles, posters and other promotional material about species at risk have been prepared and distributed in the Walpole Island First Nation community.

The general habitat for Butler’s Gartersnake was protected under the ESA when the species was uplisted to Endangered in 2010.

In the Windsor area, the construction of a divided multi-lane highway, the HGP during the period from 2011 to 2015 resulted in impacts to at least one subpopulation of Butler’s Gartersnake. Portions of the Butler’s Gartersnake subpopulations in this area were formerly found in the corridor being developed for the HGP during pre-construction surveys in 2010 and 2011. After exclusion fencing was erected along the corridor, all snakes found within the fenced construction area were relocated to adjacent habitat on the outside of the fence under a permit issued under the provincial ESA.

Mitigation efforts for Butler’s Gartersnake included developing a restoration and management plan. An ongoing mark/recapture radio telemetry study was initiated to study the effects of mitigation measures and help determine key habitat areas for Butler’s Gartersnake including hibernacula, live birthing habitat and movement corridors (LGL 2010; AMEC 2012, 2013, 2014). An extensive monitoring program, which began in 2009, has been underway to determine impacts to the subpopulations as a requirement of the permit. This includes monitoring activities such as radio tracking snakes, assessing movement behaviours of displaced snakes, monitoring the effectiveness of created habitat features (e.g., hibernacula, corridors, basking and cooling areas) and expanding the baseline knowledge of subpopulation size, distribution and behaviour. Monitoring activities will continue five years post-construction; the permit expires in 2021.

A number of stewardship and outreach activities including the development of vegetation best management practices and outreach that increases public knowledge and protection of Butler’s Gartersnake are also currently ongoing in the area of the HGP.

Large areas of habitat were also created or enhanced as one of the requirements of this permit. This included the creation of corridors of open habitat to connect fields, facilitate movements, and enhance genetic mixing, removal of non-native invasive herbaceous plant species and woody species, and the creation of additional basking sites, open foraging habitat, habitat linkage corridors and cover objects for concealment (LGL 2010). A specially designed tunnel top specifically included to function as an eco passage for snakes was also constructed. The eco-passage reconnected two Butler’s Gartersnake populations (Spring Garden ANSI and Oakwood Bush) that were separated since the construction of Huron Church Road 60 years ago.

A study to evaluate the effects of road mortality on all reptiles, including Butler’s Gartersnake, within the Ojibway Prairie remnants in Windsor and LaSalle was conducted from 2010 – 2013. The study involved a systematic road mortality survey to determine the nature and extent of reptiles found dead on roads bisecting the natural heritage features of the Ojibway Prairie Complex and surrounding natural areas. Butler’s Gartersnake was identified as having the second highest number of individuals recorded as dead on road out of the six species at risk surveyed, and was found to be threatened by road mortality within multiple road segments (Choquette 2014).

The Ojibway Nature Centre has undertaken many beneficial activities for local snake populations, including Butler’s Gartersnake, for many years. This includes activities such as conducting public outreach to educate the community on the threats facing the species, hosting educational events, habitat restoration, and land acquisition and conducting mark-recapture studies and radio-telemetry for Massasauga (Sistrurus catenatus) and Eastern Foxsnake (Pantherophis gloydi). The Ojibway Nature Centre also maintains a database of sight records and known populations of Butler’s Gartersnake.

Aamjiwnaang First Nation, with funding from the Aboriginal Fund for Species at Risk, has undertaken stewardship activities in order to reduce threats to the Butler’s Gartersnake within their community. They have erected SAR crossing signage in key areas to aid in the education and awareness of road mortality and have also conducted public outreach initiatives including informational posters and presentations, particularly for community staff. Surveying and monitoring efforts for Butler’s Gartersnake and other species at risk are ongoing on Aamjiwnaang First Nation, and habitat restoration activities are also underway.

Research to better understand the genetic structure of Butler’s Gartersnake across Ontario and examine the unique genetics and morphology of the Luther Marsh subpopulation was completed in 2013 (Noble et al. 2013). As a result of this research, it was discovered that there are four to five genetically distinct clusters of Butler’s Gartersnake in Ontario: Sarnia (1), Luther Marsh (1) and Windsor (2-3), and these clusters are subdivided into 3 or 4 subpopulations (Noble et al. 2013).

An ongoing research project focused on Butler’s Gartersnake populations and habitat in southwestern Ontario is being undertaken by AMEC Foster Wheeler, Queen’s University and University of Waterloo. This project is using occurrence records and genetic samples, to build habitat suitability models for the species and its subpopulations in the Windsor area. In addition to habitat preferences, this project will also provide information on habitat connectivity and dispersal between subpopulations, and effective population sizes within subpopulations.

6.2 Strategic direction for recovery

^a "Priority" reflects the degree to which the broad strategy contributes directly to the recovery of the species or is an essential precursor to an approach that contributes to the recovery of the species.

6.3 Narrative to support the recovery planning table

The approaches above focus on conserving and, where feasible, increasing, the distribution and abundance of extant subpopulations and remaining natural habitats, particularly between local subpopulations, of the Butler’s Gartersnake in Canada. There is also a focus on developing best management practices for Butler’s Gartersnake habitat, which can be implemented by engaging various stakeholders (e.g., private and public land owners, land users and planners, Indigenous groups, non-government organizations, governments). Habitat protection, management and restoration are of the utmost importance to recover Butler’s Gartersnake, as habitat loss and fragmentation are the major threats to this species. The emphasis of habitat protection and restoration efforts should consider both creation and maintenance of corridors between core habitats as habitat fragmentation is a significant concern particularly for urban local subpopulations. Threat mitigation such as the development of best management practices to address road mortality and strategic restoration practices to combat invasive species will also be essential. Because there is uncertainty regarding site specific characteristics of certain components of Butler’s Gartersnake habitat (e.g., hibernacula and live birthing sites), it will be necessary to determine the habitat requirements for these life processes so that existing and former suitable habitat may be prioritized for restoration. The extent of the impacts of road networks will also need to be examined. The significance of Snake Fungal Disease to Butler’s Gartersnake is unknown at present; however, there is concern for small populations of conservation concern if infections result in mortalities. Continued research on the genetic structure of the Canadian population of Butler’s Gartersnake is needed to determine whether inbreeding depression and or/hybridization is occurring in any of the extant subpopulations in Ontario.

7. Critical habitat

7.1 Identification of the species' critical habitat

Section 41(1)(c) of SARA requires that recovery strategies include an identification of the species’ critical habitat, to the extent possible, as well as examples of activities that are likely to result in its destruction. Under section 2(1) of SARA, critical habitat is “the habitat that is necessary for the survival or recovery of a listed wildlife species and that is identified as the species’ critical habitat in the recovery strategy or in an action plan for the species”.

Critical habitat identification for Butler’s Gartersnake must describe the habitat necessary to maintain the current subpopulations and distribution and promote connectivity between local subpopulations where feasible (see section 5). This federal recovery strategy identifies critical habitat for 27 extant locations of Butler’s Gartersnake in Canada, within the geographic regions of Windsor, Sarnia and Luther Marsh (see Figures 4, 5, and 6 and also Table 3) and based on best available information as of June 2014. Additional critical habitat may be added in the future if new information supports the inclusion of areas beyond those currently identified. In some of the areas identified as critical habitat, the quality of the habitat will need to be improved for recovery to be achieved.

It is recognized that the critical habitat identified below is insufficient to achieve the population and distribution objectives for the species because there are locations that may still support Butler’s Gartersnake but have not been adequately or recently surveyed, or that may be contributing to local subpopulation viability but critical habitat could not be identified due to a lack of certainty in the data. A schedule of studies (section 7.2; Table 4) has been developed that outlines the activities required to complete the identification of critical habitat in support of the population and distribution objectives. The identification of critical habitat will be updated, as required, either in a revised recovery strategy or an action plan once these studies are completed.

The identification of Butler’s Gartersnake critical habitat is based on three criteria: habitat occupancy, habitat suitability and habitat connectivity between local subpopulations, which are discussed in detail below.

7.1.1 Habitat occupancy

This criterion refers to areas where there is a reasonable degree of certainty of current use by the species (an indicator of habitat suitability).

Habitat is considered occupied when:

• At least one Butler’s Gartersnake individual has been observed in any single year since 1994.

Habitat occupancy is based on documented live birthing or hibernacula locations, survey and radio telemetry data, and incidental observations of Butler’s Gartersnakes (live or dead) in locations where key biophysical attributes are present nearby. These observational data must have a spatial precision of ≤ 1 km or provide enough detail to be associated with a specific suitable habitat feature(s) to be considered adequate to identify critical habitat.

Most available records are from the past ten years, from the 2010 COSEWIC status report and from survey and monitoring work undertaken in relation to the Detroit River International Crossing (DRIC) and HGP and surrounding areas (AMEC 2013). However, the species is challenging to track and monitor and difficult to find in its preferred habitat outside of the mating season (COSEWIC 2010). Due to the fact that the species is fairly cryptic and longevity in the wild is currently unknown (maximum recorded age in captivity is 14 years old; COSEWIC 2010), the timeframe of twenty years is deemed appropriate to allow for the inclusion of a number of local subpopulations that likely persist but have not been targeted by recent surveys or may have gone undetected.

Locations with records older than twenty years require surveys to confirm the species’ occupancy and persistence of critical habitat (section 7.2).

Critical habitat is not identified for locations where recent surveys or other information (e.g., aerial photos) determined that the location no longer contains habitat (e.g., housing development) to support Butler’s Gartersnake (i.e., extirpated) or where significant portions of habitat have been destroyed (e.g., ‘unknown’ status) (See Appendix B). Locations recently surveyed but where no Butler’s Gartersnakes were observed, but the habitat appears to remain suitable were considered ‘unknown’, requiring additional surveys to confirm current use by Butler’s Gartersnake (See Appendix B, section 7.2).

For clarity, Butler’s Gartersnakes located within the DRIC Plaza site and HGP footprint were relocated into existing suitable habitat or restored habitat (the majority of these restoration sites occur within the Ojibway Prairie complex and surrounding areas in Windsor, Ontario). The HGP relocation sites are included in the identification of critical habitat as many of the sites already supported Butler’s Gartersnakes; the DRIC Plaza relocation site (Black Oak Heritage Park) may be included in the future as more information becomes available (i.e., if the relocation proves to be successful since there was not an existing subpopulation at this location). Any observations from within the DRIC Plaza site or the HGP footprint where road construction and expansion has occurred and mitigation/relocation of individuals was carried out are not identified as critical habitat at this time. A large amount of land (>35 ha) within the current HGP construction footprint is to be restored back to snake habitat under the provincial ESA permit, and it is expected that Butler’s Gartersnake will recolonize these formerly occupied areas once restoration activities are completed and habitat becomes available. Critical habitat will be revisited as additional information on the success of this restoration project becomes available.

7.1.2 Habitat suitability

Habitat suitability relates to areas possessing a specific set of biophysical attributes that support individuals of the species carrying out essential aspects of their life cycle (i.e. live birthing, thermoregulation, mating, foraging and hibernation) as well as their movements. Suitable habitat for Butler’s Gartersnake can therefore be described as a conglomerate within grassland or other open/semi-open habitat mosaics, in which specific biophysical attributes can be associated with essential life stages and needs. Within the area of suitable habitat, the biophysical attributes required by Butler’s Gartersnake will vary over space and time with the dynamic nature of ecosystems. In addition, particular biophysical attributes will be of greater importance to snakes at different points in time (e.g., during different life processes, seasons or at various times of the year).

The biophysical attributes of critical habitat include the characteristics described below.

For live birthing, thermoregulation, mating, foraging, and hibernation:

• Open to early-successional areas with sparse to dense grasses (e.g., tallgrass prairie communities, grasslands, cultural meadows, thicket, old fields or deciduous swamps that contain access to wet areas (e.g., seeps, wet depressions surrounded by higher and drier land).
• Edges of habitat types as described above (e.g., edges of wet depressions, forested areas and cultural thickets).
• For hibernation: areas that contain crayfish burrows, small mammal burrows or dens, log piles, drains, dogwood bushes, or rocky outcrops.

For movement:

• Habitat and/or land cover types that are permeable to Butler’s Gartersnake; not interrupted by barriers to movement (i.e., major paved roads, untraversable habitat such as cliffs, dense upland forests, dense urbanized developments, and large bodies of open water).

Suitable habitat for Butler’s Gartersnake may be partially described using the Ecological Land Classification (ELC) framework for Ontario (from Lee et al. 1998)^{footnote 26[26]}, which provides a standardized approach to the interpretation and delineation of dynamic ecosystem boundaries. The ELC approach classifies habitats not only by vegetation community but also considers hydrology and topography, and as such encompasses the biophysical attributes of the habitat for Butler’s Gartersnake. In addition, ELC terminology and methods are familiar to many land managers and conservation practitioners who have adopted this vegetation community classification tool as the standard approach for Ontario.

The biophysical attributes of Butler’s Gartersnake suitable habitat for live birthing, thermoregulation, mating, foraging, and hibernation are typically found in the following ELC Community Series designations: Open Tallgrass Prairie (TPO), Tallgrass Savanna (TPS), Cultural Meadow (CUM), Cultural Thicket (CUT), Cultural Savanna (CUS), Deciduous Swamp (SWD), Meadow Marsh (MAM), and Shallow Marsh (MAS). Due to their rarity, confirmed hibernacula will also be identified as critical habitat wherever they are located (they do not need to occur in ELC polygons; see below). Movement habitat (commuting and dispersal) is also not described using the ELC framework. Instead it refers to any contiguous^{footnote 27[27]} habitat (free from barriers to the species’ movement) that connects adjacent suitable ELC habitat patches for live birthing, thermoregulation, mating, foraging, and hibernation and/or hibernacula.

Given the lack of information on minimum habitat quantities required for life cycle activities within a home range, the following approach has been used to identify functional habitat for Butler’s Gartersnake. This description of suitable habitat reflects the fact that certain biophysical attributes do not need to be immediately adjacent to each other, as long as they remain connected so that the individuals can easily move between them to meet all their biological needs and respond to or avoid disturbances as required. The distances determining the extent of suitable habitat are specific to Butler’s Gartersnake and based on the species’ biological and behavioural requirements (see section 3.3).

Suitable habitat for Butler’s Gartersnake consists of live birthing, thermoregulation, mating, and foraging habitat, and hibernacula (throughout the home range for at least one individual) and the movement (commuting and dispersal) habitat that occurs between them (see Figure 3), and is described as follows:

• The entire suitable live birthing, thermoregulation, mating, foraging, or hibernation habitat patch(es) (i.e., the entire ELC community series polygon) or known hibernaculum located within 200 m of an observation of Butler’s Gartersnake (i.e. meets the occupancy criteria);
  
  AND
• The contiguous movement (commuting and dispersal) habitat(s) between them, being permeable to Butler’s Gartersnake movement (i.e., no barriers) and occurring with 200 m of an observation of Butler’s Gartersnake.

Movement habitat is only considered where it creates a continuous linkage between two or more live birthing, thermoregulation, mating, foraging, and hibernation habitat patches and/or hibernacula (Figure 3). Barriers to Butler’s Gartersnake include major paved roads or roads with obstructions such that Butler’s Gartersnake rarely if ever cross successfully; untraversable topography (e.g., cliff); dense urbanized areas lacking suitable habitat and large bodies of open water (Carpenter 1952; COSEWIC 2010; LGL 2011; Noble et al. 2013).

Suitable habitat for hibernacula is defined as:

• The area, both natural and man-made, within a 150 m radial distance of a Butler’s Gartersnake hibernaculum entrance and/or exit, and which meets the habitat occupancy criterion.

The search for live birthing sites, hibernacula, shelter from heat and cold, and food constitute the majority of movements for snakes (Carpenter 1952). The 200 m distance is based on the average home range lengths observed for radio-tracked individuals over a four-year Ontario study (average 218 m) (AMEC 2012, 2013, 2014, 2015). These movements demonstrate that critical habitats (e.g., foraging, thermoregulation habitats) are available within several areas of their home range. A habitat-based approach (functional habitat) is important to preserve the habitat remnants that remain occupied and available to Butler’s Gartersnake. This is due to the fact that suitable habitat occupied by Butler’s Gartersnakes is very fragmented within the landscape and development pressures for housing and road construction are high.

Hibernacula are one of the most important habitat features for Butler’s Gartersnake and require special consideration. They are critical for over winter survival (Shoemaker et al. 2009; LGL 2010). Hibernacula are also difficult to identify due to their small entrance points and the cryptic habits of the snakes entering and exiting the hibernacula. It is not currently known to what extent subterranean features of hibernacula extend from an entrance or exit point. A 150 m radius area is considered necessary to maintain the biological composition, structure and function of the surrounding subterranean environment (Rossman et al. 1996; M. Hazell pers. comm. 2014) and to protect staging areas in the vicinity of the hibernacula. Butler’s Gartersnakes have been located underground 30 m away from their original hibernacula site in Ontario (AMEC 2013) and the additional area may support the soil/substrate suitability and certain moisture regimes around this extent of hibernacula use. Recent data in Ontario indicates that Butler’s Gartersnake hibernacula are typically over 150 m from other core areas used during the active season, and the species may select hibernacula up to 100 m from the previous year’s location, (AMEC 2013, 2014). This criterion may be refined in the future as more hibernacula for Butler’s Gartersnake are discovered and additional information on their structure and use by the species becomes available.

Butler’s Gartersnakes are readily found individually or in small groups under various types of materials including rocks, concrete, plywood boards, roofing shingles, metal tins, old carpet, rubber, cardboard, and fiberglass sheets (COSEWIC 2010). Since many of the Butler’s Gartersnake populations currently persist in highly degraded habitats (e.g., urban parks, railroad right-of-ways, etc.) and rely on man-made cover, these features are important components of the species’ habitat (COSEWIC 2010). Where feasible, these man-made features should be left in place to provide areas for foraging, cover, and thermoregulation when they occur in or immediately adjacent to critical habitat.

Active agricultural fields in row crops or in crop rotation are considered unsuitable habitats and are excluded from critical habitat (including hibernacula) as they are poor quality habitats offering limited cover and use of these habitats can result in increased rates of mortality; also these habitats may become ecological traps^{footnote 28[28]}. Marginal lands (i.e., idle land >10 years) and unimproved pasture are considered suitable habitats (i.e., cultural meadow).

7.1.3 Habitat connectivity

Connectivity between local subpopulations is important for immigration and emigration (movement into and out of subpopulations, respectively) which increases gene flow (maintaining genetic diversity) and allows the species to react to environmental stressors (e.g., pollution, droughts, habitat alterations) by moving to another location. In Canada, habitat loss and fragmentation is the greatest threat to Butler’s Gartersnake; many local subpopulations are distributed in small, mostly isolated patches within an urban landscape (e.g., high housing and road development pressures). This can result in the loss of dispersal corridors, isolating local subpopulations and causing reductions in genetic diversity. Habitat connectivity is necessary to meet the population and distribution objectives.

To allow short-distance movements needed to complete the Butler’s Gartersnake life cycle (commuting movement), connectivity is ensured by the defined functional habitat (seasonal movements between habitats (e.g., between hibernacula and live birthing sites) as required to complete an annual life cycle) (section 7.1.2)). To allow long distance movements such as immigration or emigration to promote genetic stability within local populations (dispersal movement), the habitat connectivity criterion connects local subpopulations based on the documented tendency of Butler’s Gartersnakes to undertake terrestrial movements for dispersal^{footnote 29[29]}.

The habitat connectivity criterion identifies unoccupied^{footnote 30[30]} suitable habitat as critical habitat where it occurs within a dispersal distance of two individuals’ home ranges, and is defined as:

• The movement (commuting or dispersal) habitat (s) where it creates a contiguous linkage between two (or more) functional habitats separated by up to a maximum distance of 600 m.

The 600 m distance is based on the maximum home range length for radio-tracked individuals of Butler’s Gartersnake observed over a four-year period in Ontario (max. 662 m in 2012) (AMEC 2012, 2013, 2014, 2015) and is three times the average linear home range length (200 m), which is the minimum separation distance between local populations recommended by NatureServe (NatureServe 2017) to maintain connectivity and reduce the probability of genetic isolation. This distance is appropriate given the imminent threats to the species and its continued decline in Canada (COSEWIC 2010). Estimates of dispersal for Butler’s Gartersnake vary; most movement studies showcase localized movements (LGL 2010). The species will, however, move large distances at certain times of its life cycle (e.g., females observed moving up to 395 m to birthing sites in the spring and summer, snakes searching for hibernacula in late summer or fall [LGL 2010] and young of the year moving more than 400 m from their activity areas, likely to establish new territories [LGL 2011]).

Because a major road (e.g., multi-laned paved road) or other large paved surface (e.g., parking lot) between occupied functional habitats usually results in Butler’s Gartersnake mortality, the area is not identified as part of the movement corridor (if it exists) unless a culvert or tunnel underneath it is present. In those cases, the movement corridor may be considered the width of that culvert or tunnel and would require verification in the field.

1. Functional suitable habitat is identified for Butler’s Gartersnake as the entire suitable ELC community series polygon where it occurs within 200 m of an observation and the movement habitat between them, up to 200 m from an observation. Hibernacula suitable habitat is identified as the area within 150 m of a hibernaculum entrance or exit, and may or may not exist within functional habitat (see section 7.1.2.).
2. A critical habitat unit includes the boundary of functional habitat and/or hibernacula suitable habitat that meets the habitat occupancy criterion. The critical habitat unit boundary is extended (using a minimum bounding polygon) where two or more functional habitats and/or hibernacula suitable habitats are separated by up to a maximum distance of 600 m and contain habitat suitable for movement (dispersal) between them (free from barriers).

7.1.4 Application of the Butler’s Gartersnake critical habitat criteria

Critical habitat for Butler’s Gartersnake includes the suitable habitat (i.e., functional habitat or hibernacula) (section 7.1.2), that meets the habitat occupancy criterion (section 7.1.1), herein referred to as a critical habitat unit. The critical habitat unit bounds a functional habitat complex for Butler’s Gartersnake, consisting of core habitat areas based on ELC and/or hibernacula suitable habitat and areas permeable to the species’ movement. Where the habitat connectivity criterion is applied (in cases where two or more functional or hibernacula suitable habitats are separated by up to a maximum dispersal distance of 600 m, section 7.1.3), the critical habitat unit is extended (using a minimum bounding polygon) identifying a larger habitat complex for Butler’s Gartersnake (Figure 3). Thus, the critical habitat unit represents the maximum extent of critical habitat at a particular location.

Application of the critical habitat criteria to the best available data current to June 2014 identified critical habitat for the 27 known extant locations of Butler’s Gartersnake in Canada, within the Windsor, Sarnia and Luther Marsh regions of Ontario. The critical habitat identified is considered a partial identification of critical habitat and is insufficient to meet the population and distribution objectives. Available information on the species and subpopulation status at a number of locations is unknown, outdated or lacking detailed spatial references or unavailable to Environment and Climate Change Canada. Specifically, critical habitat could not be identified for locations at Skunk’s Misery, Parkhill, or nine locations within the Windsor-Sarnia region (including Walpole Island) with unknown subpopulation status and four historical locations (see section 3.2 and Appendix B). A schedule of studies (section 7.2) has been developed to provide the information necessary to complete the identification of critical habitat that will be sufficient to meet the population and distribution objectives. As additional information becomes available, critical habitat may be refined or more units meeting critical habitat criteria may be added.

The portions of critical habitat that had extended into the development footprints of the DRIC Plaza site and HGP are not identified as critical habitat. All Butler’s Gartersnakes previously occurring within the DRIC Plaza site and HGP footprints were relocated into existing or restored habitat.

Critical habitat for Butler’s Gartersnake is presented using 1 x 1 km UTM grid squares. The UTM grid squares presented in Figures 4, 5 and 6 are part of a standardized grid system that indicates the general geographic areas containing critical habitat, which can be used for land use planning and/or environmental assessment purposes. In addition to providing these benefits, the 1 x 1 km UTM grid respects provincial data-sharing agreements in Ontario. Critical habitat within each grid square is defined by the criteria described in section 7.1.1 through 7.1.3. More detailed information on critical habitat to support protection of the species and its habitat may be requested on a need-to-know basis by contacting Environment and Climate Change Canada – Canadian Wildlife Service at ec.planificationduretablissement-recoveryplanning.ec@canada.ca.

^a Based on the standard UTM Military Grid Reference System (see http://www.nrcan.gc.ca/earth-sciences/geography/topographic-information/maps/9789), where the first 2 digits and letter represent the UTM Zone, the following 2 letters indicate the 100 x 100 km standardized UTM grid. This unique alphanumeric code is based on the methodology produced from the Breeding Bird Atlases of Canada (See http://www.bsc-eoc.org/ for more information on breeding bird atlases).

^b The listed coordinates are a cartographic representation of where critical habitat can be found, presented as the southwest corner of the 100 x 100 km standardized UTM grid square containing all or a portion of the critical habitat unit. The coordinates may not fall within critical habitat and are provided as a general location only.

^c Land tenure is provided as an approximation of the types of land ownership that exist at the critical habitat units and should be used for guidance purposes only. Accurate land tenure will require cross referencing critical habitat boundaries with surveyed land parcel information.

7.2 Schedule of studies to identify critical habitat

Critical habitat for Butler’s Gartersnake is partially identified in this recovery strategy, and is considered insufficient to meet the population and distribution objectives (section 5) for the species. There are locations that may still support Butler’s Gartersnake that i) have not been recently or sufficiently surveyed or ii) may be contributing to overall local subpopulation viability but critical habitat could not be identified due to a lack of certainty in the data. Within the areas where Butler’s Gartersnakes were not confirmed in 2009 (Skunk’s Misery, Parkhill, 9 locations within the Windsor-Sarnia region including Walpole Island listed with an unknown subpopulation status, and 4 locations listed with a historical subpopulation status) (COSEWIC 2010), extensive surveying using proper survey methods to determine detection probabilities is required.

7.3 Activities likely to result in the destruction of critical habitat

Understanding what constitutes destruction of critical habitat is necessary for the protection and management of critical habitat. Habitat destruction is determined on a case-by-case basis. Destruction would result if part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from one or several activities occurring at one point in time, or from the cumulative effects of one or more activities over a prolonged period. Table 5 provides examples of activities likely to destroy critical habitat of the species based on where the activity takes place and the component(s) of critical habitat affected, however, it does not represent an exhaustive list of all activities likely to destroy critical habitat.

Destruction of critical habitat for Butler’s Gartersnake can result from activities undertaken at a variety of scales. Destruction may occur from an activity, or activities, either within or outside the critical habitat unit, and may occur in any season of the year. Restricted or permitted activities that may occur within the critical habitat unit are evaluated based on the species’ functional requirements (components of functional habitat, hibernacula suitable habitat and/or connective habitat) of the portion(s) of impacted area. For example, some activities may be permitted in the movement (commuting and dispersal) habitat(s) within a critical habitat unit (functional habitat and/or connective habitat) that would be restricted within the live birthing, thermoregulation, mating, foraging, hibernation and movement component of the functional habitat, as these are heavily used by Butler’s Gartersnakes and are of the utmost importance to the species’ habitat needs. In this case, certain activities would not be considered destruction of the movement (commuting and dispersal) habitat(s) as long as sufficient habitat permeability (no barriers) is maintained, consistent with the species’ functional requirements of that habitat. This information must be integrated in the case-by-case analysis when evaluating restricted/permitted activities. Some activities can result in the destruction of critical habitat, even if they occur outside the boundaries of the critical habitat unit. These instances will need to be evaluated on a case-by-case basis to determine what restrictions or mitigation should be put in place to prevent the destruction of critical habitat (e.g., housing and industrial development, creation or expansion of roads, drainage of wetlands).

Due to Butler’s Gartersnakes’ use of habitat features seasonally, it may be possible to mitigate some impacts on critical habitat through the timing of activities. Timing of the activity and whether it would result in destruction of critical habitat will need to be discussed with the appropriate agencies (generally, the province of Ontario (Ontario Ministry of Natural Resources and Forestry) on non-federal lands, and Environment and Climate Change Canada on federal lands) on a case-by-case basis.

8. Measuring progress

The performance indicators presented below provide a way to define and measure progress toward achieving the population and distribution objectives.

Every five years success of recovery strategy implementation will be measured against the following performance indicators:

• Distribution and current abundance of extant subpopulations of Butler’s Gartersnake are maintained and, where biologically and technically feasible, increased within their historic range in Canada.
• Habitat connectivity between local subpopulations is improved.

9. Statement on action plans

One or more action plans will be completed for Butler’s Gartersnake by December 2025.

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Appendix A: Effects on the environment and other species

A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals^{footnote 31[31]}. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision-making and to evaluate whether the outcomes of a recovery planning document could affect any component of the environment or any of the Federal Sustainable Development Strategy’s^{footnote 32[32]} (FSDS) goals and targets.

Recovery planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that strategies may also inadvertently lead to environmental effects beyond the intended benefits. The planning process based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts on non-target species or habitats. The results of the SEA are incorporated directly into the strategy itself, but are also summarized below in this statement.

This recovery strategy will clearly benefit the environment by promoting the recovery of the Butler’s Gartersnake. The potential for the strategy to inadvertently lead to adverse effects on other species was considered. Many at risk and rare species occur in tallgrass prairie habitats. Therefore, it is expected that recovery efforts for Butler’s Gartersnake will also benefit many other species that occur in these habitats, such as Colicroot (Aletris farinosa), Dense Blazing Star (Liatris spicata), Willowleaf Aster (Symphyotrichum praealtum), and Eastern Foxsnake (Pantherophis gloydi). Habitat securement, policy, and stewardship approaches are not expected to have any adverse effects on habitat or co-occurring species. The SEA concluded that this strategy will clearly benefit the environment and will not entail any significant adverse effects. The reader should refer to the following sections of the document in particular: Population and Distribution Objectives and Strategic Direction for Recovery.

Appendix B: Subpopulations of Butler’s Gartersnake in Canada

For the purposes of this recovery strategy, subpopulations are identified based on the description of Butler’s Gartersnake locations in the 2010 COSEWIC status report and are provided below.

Most locations were visited to obtain information for the COSEWIC status report (2010) unless they were considered extirpated (e.g., lost to development). Some locations were not surveyed because significant portions of habitat for the Butler’s Gartersnake appeared destroyed. These locations are given an 'unknown' status until extirpation is confirmed. Locations where the last observation date is >20 years are identified as 'historical'. Locations recently visited, but where no Butler’s Gartersnake were observed and suitable habitat remains available to the species (determined from field visits or air photos), these locations are also given ‘unknown’ status. Additional surveys are required to confirm subpopulation status at these locations. A schedule of studies identifies additional surveys at historical and unknown locations to confirm the status of Butler’s Gartersnake. New locations for Butler’s Gartersnake have been found, not previously identified in the literature. New information has not yet been formally assessed by the Ontario Conservation Data Centre (Ontario Natural Heritage Information Centre). In the future, the enumeration of Butler Gartersnake locations may better align with element occurrence information.

^a Status has changed to extant since the 2010 COSEWIC report, due to more recent observations.