Timber Rattlesnake Evaluation

Committee on the Status of Species at Risk in Ontario (COSSARO) Assessed by COSSARO as Extirpated

February 2011

Part 1: COSSARO Candidate Species at Risk Evaluation form

Timber Rattlesnake (Crotalus horridus)

Current designations:

GRANK – G4 (NatureServe 2011)

NRANK Canada – NX (NatureServe 2011)

COSEWIC – Extirpated (November 2010; COSEWIC 2011)

SARA – Extirpated (Schedule 1; Environment Canada 2011)

General Status Canada – Extirpated (Wild Species 2005)

ESA 2007 – Extirpated (OMNR 2011)

SRANK – SX (NatureServe 2011)

General Status Ontario – At Risk (Wild Species 2005)

Distribution and status outside Ontario:

Distributed throughout much of the eastern/southeastern United States, although distribution is spotty and not continuous, particularly along the western and northern edges of the range (NatureServe 2011). Occurs in 32 USA states from Texas in the southwest to New Hampshire in the northeast; considered extirpated in Rhode Island, Maine and Ontario (NatureServe 2011).

Eligibility criteria

Native status

Yes - A native species in Ontario at the northern edge of its range.

Taxonomic distinctness

Yes - Pisani et al. (1972) examined morphological variation in primarily the midwestern portion of the range and concluded that the recognition of subspecies is not warranted; (from Zammit and Oldham 2000). No evidence of subspeciation based on mtDNA variation (Clark et al. 2003)

Designatable units

Original Ontario distribution along the Niagara Escarpment, and there is no additional information to suggest there should be more than one designatable unit.

Priority-setting criteria

Recent arrival

No - No indication that it was a recent arrival in Ontario.

Non-resident

No - No indication that it was not a naturally occurring species in Ontario.

Primary criteria (rarity and declines)

1. Global rank

Not in any category - Global rank of G4 (Apparently Secure) based on the species' large range in the eastern USA, although it is recognized that its occurrence is spotty in many regions and many populations have been depleted or exterminated and are declining (NatureServe 2011).

2. Global decline

Threatened - Global short-term decline of 10-30% and long-term decline of 25-50% (NatureServe 2010). Global area of occupancy, number of subpopulations and population size are all still declining at an estimated rate of more than 10% over 3 generations (20-30 years) (NatureServe 2011).

3. Northeastern North America ranks

Threatened - Ranked S1, S2, SH, or SX in 12 of 20 northeastern North American jurisdictions (60%) (Appendix 1), and considered extirpated in Maine, Rhode Island and Ontario ( NatureServe 2011).

4. Northeastern North America decline

Endangered - Declining or extirpated in all northeastern USA states – "an overall consensus among virtually all scientists and field observers is that the timber rattlesnake indeed is declining over most parts of its range" (NatureServe 2011). Martin (1982) reported that most observers in the northeast believed that most denning populations were reduced to 15-20% of the levels 40 years previous.

5. Ontario occurrences

Endangered - No extant occurrences, 8 historic occurrences. (NHIC 2011). Formerly occurred at Point Pelee and Pelee Island, Essex Co.; Bradley’s Marsh, Kent Co.; Fitzwilliam Island, Manitoulin District; Campbellton, Elgin Co.; Credit River near Rockside, Peel Co.; and along the southern portion of the Niagara Escarpment (i.e. Spencer George and East Hamilton, Hamilton-Wentworth RM; vicinity of Rattlesnake Point and Watertown, Halton Co.; and Niagara Glen, Niagara RM) (Zammit and Oldham 2000). Most recent credible record was the Niagara Peninsula in 1941.

6. Ontario decline

Endangered - Zero extant Ontario occurrences, and absent from 100% of documented Ontario sites.

7. Ontario’s conservation responsibility

Not in any category – Former Ontario range represented much less than 10% of global range; current Ontario range represents 0% of global range.

Secondary criteria (threats and vulnerability)

1. Population sustainability

Endangered – Species is no longer present in Ontario and is thus clearly "unlikely to sustain itself in Ontario".

2. Lack of regulatory protection for exploited wild populations

Not in any category - Some former locations are now within parks and protected areas such as the Fish Point Nature Reserve on Pelee Island, Point Pelee National Park, and Hamilton or Halton Region Conservation Authority properties (Zammit and Oldham 2000). Species' protection provided by the Endangered Species Act, 2007.

3. Direct threats

Not in any category - This criterion cannot reasonably be applied to an extirpated species. Timber Rattlesnakes in Ontario probably were exterminated largely by people who deliberately killed large numbers of snakes. In Ontario, mortality rates were probably unsustainably high until the species was completely eradicated as a result of direct human persecution and habitat loss. Other than anecdotal information, information about threats in Ontario is lacking. Since 1719, timber rattlesnakes have been the object of "rattlesnake roundups" and bounty hunting, whereby fees were paid for killing undesirable species (Casper and Hay 1998). For example, in Wisconsin, bounty records showed a 70-80% decline over a seven year period (1965-1972), and in Minnesota, bounty records declined from 4,955 in 1980 to 191 in 1987 (a 96% decrease). In addition to human persecution, habitat loss, habitat fragmentation and isolation of populations, human-caused mortality and road mortality would continue to threaten the species if it were present today (NatureServe 2011).

4. Specialized life history or habitat-use characteristics

Endangered - Communal denning habit makes this species particularly vulnerable to habitat alteration. This denning habit also facilitated the large-scale killing of the species either for bounty or as part of organized snake "round-ups" (NatureServe 2011).

COSSARO criteria met (primary/secondary)

Endangered– [3/2]
Threatened – [2/0]
Special concern – [0/0]

Recommended status: Extirpated

Summary

Timber Rattlesnake, Crotalus horridus, has been Extirpated from Ontario. These snakes occur throughout the eastern and central United States, although they are locally extirpated or declining in many areas especially in the northeast jurisdictions. The most recent confirmed record of the species in Ontario was made in the Niagara Gorge in 1941. More recent sightings elsewhere in the province are probably erroneous. The species former range may have included Pelee Island and Point Pelee, the Niagara Escarpment, and possibly islands in Georgian Bay. Although the Timber Rattlesnake is currently listed under Ontario’s Endangered Species Act, most authorities have concluded that this snake is extirpated from Ontario. Based on COSEWIC criteria, we arrive at an Extirpated status as there has been no confirmed record in over 50 years.

Information sources

Casper, G. and R. Hay 1998. Timber Rattlesnake web page. Milwaukee Public Museum website http://www.mpm.edu/collect/vertzo/herp/timber/status.htm [link inactive]

Clark, A.M., P.E. Moler, E.E. Possardt, A.H. Savitz, W.S. Brown and B.W. Bowen. 2003. Phylogeography of the Timber Rattlesnake (Crotalus horridus) based on mtDNA sequences. Journal of Herpetology 37(1): 145-154. (from COSEWIC 2010)

Conant, R. and J.T. Collins 1991. A field guide to reptiles and amphibians: eastern and central North America. Third edition. Houghton Mifflin Co., Boston, Massachusetts. 450 pp.

Cook, F.R. 1984. Introductions to Canadian amphibians and reptiles. National Museum of Canada, Ottawa. 200 pp. (from Zammit and Oldham 2000)

COSEWIC. 2010. COSEWIC status appraisal summary on the Timber Rattlesnake Crotalus horridus. Committee on the Status of Endangered Wildlife in Canada. Ottawa. ix pp.

COSEWIC 2011. Environment Canada Wildlife Species Search: Timber Rattlesnake. http://www.cosepac.gc.ca/eng/sct1/searchform_e.cfm. [link inactive] Accessed Feb. 2 2011

Environment Canada 2011. Environment Canada Species at Risk Public Registry: Timber Rattlesnake. Accessed Feb. 2 2011

Martin, W.H. 1982. The Timber Rattlesnake in the northeast: its range, past and present. Bulletin of the New York Herpetological Society 15:15-20. (from NatureServe 2011)

NatureServe 2011. NatureServe Explorer An online encyclopedia of life: Timber Rattlesnake. Accessed Feb. 2 2011

NHIC 2011.

OMNR 2011. Species at Risk in Ontario (SARO) List

Pisani, G.R., J.T. Collins and S.R. Edwards. 1972. A re-evaluation of the subspecies of Crotalus horridus. Transactions of the Kansas Academy of Science 75(3): 255-263.

Wild Species 2005. Timber Rattlesnake. http://www.wildspecies.ca/wildspecies2005/search.cfm?lang=e&sec=9 [link inactive] Accessed Feb. 2 2011.

Zammit, A.E. and M.J. Oldham. 2000. COSSARO candidate V,T,E species evaluation form for Timber Rattlesnake (Crotalus horridus). Natural Heritage Information Centre, Peterborough ON. 12 pp.

Appendix 1 – Timber Rattlesnake G4

Northeastern North America rank, status and decline

(NatureServe 2011)^{footnote 1[1]}

Occurs as a native species in 20 of 28 northeastern jurisdictions SRANK or equivalent information available for 20 of 20 jurisdictions = 100 % S1, S2, SH, or SX in 12 of 20 = 60 %

Part 2: Ontario evaluation using COSEWIC criteria

Regional (Ontario) COSEWIC criteria assessment

Criterion A – Decline in total number of mature individuals

Not applicable – Population is extirpated so no decline in past 10 years.

Criterion B – Small distribution range and decline or fluctuation

Not applicable – Meets Criteria B1 and B2, but because the population is extirpated does not meet any of a (severely fragmented), b (continuing decline), or c (extreme fluctuations).

Criterion C – Small and declining number of mature individuals

Not applicable – Definitely fewer than 2500 individuals, but does not meet C1 or C2 because there is no continuing decline.

Criterion D – Very small or restricted total population

Endangered – Meets Criteria D1 (fewer than 250 mature individuals)

Criterion E – Quantitative analysis

Not applicable – No quantitative analysis has been done, although clearly the probability of extinction in the wild is greater than 20%.

Rescue effect

No – Unassisted rescue from adjacent jurisdictions is unlikely, due to declining populations along the northern edge of the species' range in the USA. There are no extant populations adjacent to Ontario, the species does not disperse long distances, and there are human development barriers between extant populations in the USA and suitable habitat in Ontario. "Natural colonization of its former Canadian range seems nearly impossible" (COSEWIC 2010).

Extirpated

• "50 years have passed since the last credible record of the species, despite surveys in the interim".
• "there is sufficient information to document that no individuals of the species remain alive"