Factors that affect moose survival
How moose are affected by climate change, habitat, hunting, parasites, disease, bears and wolves.
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A healthy and sustainable population of moose is important to Ontario.
These are some of the factors that influence moose in Ontario.
In most parts of the province, hunting has an important effect on the population of moose.
Ontario has more moose hunters than moose, at about:
- 91,000 provincially licensed moose hunters
- 78,000 moose in huntable areas (another 13,200 moose live in areas that aren’t hunted)
Harvest management system
Ontario introduced the selective harvest system in 1983 to manage the moose harvest. Harvesting opportunities focus mainly on calves then on bulls, while cows are generally more protected for reproduction.
Moose harvest is also managed by:
- adjusting season timing and length
- area (e.g., Ontario’s Wildlife Management Units)
- regulating the type of firearms used
- allocating hunting opportunities
- delivering communication and education strategies
These measures are used to influence harvest levels in response to population trends and the number of bulls, cows and calves observed during aerial surveys. The proper composition of the moose population affects overall survival and reproductive rates, and promotes moose population health.
The key elements in applying the system are:
- developing sustainable harvest plans, which includes:
- considering population status relative to objectives
- setting biologically appropriate levels and proportions of bull, cow and calf harvest
- allocating tags to resident hunters and tourism outfitters
The selective harvest system has been successful, but new challenges have emerged and our understanding has changed.
Ontario’s moose population grew from more than 80,000 moose in the early 1980s to about 115,000 in the early 2000s. But over the past decade, the population peaked and has since declined to an estimated 91,200 moose. The demand for moose hunting remains high.
Factors such as climate change and parasites may be putting more stress on moose. In addition, recent science suggests we need to reconsider how hunter harvest influences calf recruitment into the adult population.
Moose hunting trends in Ontario
Moose hunting has changed a great deal since the early 1980s, when the selective harvest system was introduced. Hunting success rates for moose are higher today. As a result, fewer adult validation tags can be issued today to achieve the same level of moose harvest.
|Moose population||80,000||91,200 (115,000 peak)|
|Season length||2-4 weeks||2-3 months|
|Road access||Less road access in many WMUs||Increased road access|
|All-terrain vehicles||Limited use||Very common use|
|Wireless communication||Limited use||Very common use|
|Party hunting||No party hunting (no party harvest)||Party hunting|
|Success rate||20-30% gun; 5-10% bow||40-50% gun; 20-30% bow|
|Calf harvest||Very limited||Substantial in many WMUs|
|Tags||Est. 47,000 adult validation tags (1984)||10,757 adult validation tags for resident hunters (2018)|
In recent years, Ontario has seen a decrease in the provincial moose population and a corresponding decrease in available adult validation tags and moose harvest.
What we’re doing
Moose populations may benefit from changes to harvest management in some areas.
Over the last decade, Ontario’s moose population, while healthy overall:
- has declined in some parts of the north
- has generally fared better in the southern part of the range
Tag reductions, and recent changes to hunting regulations, have been used to address concerns about moose populations in Ontario.
These concerns centre on:
- the low and, in some cases, declining recruitment of calves into the breeding population
- the timing of the rut, or breeding period for moose, relative to the timing of hunting seasons
In southern Ontario, where hunting seasons are very limited and moose have fared better, modest increases in hunting opportunities may be considered in coming years.
Aboriginal and treaty rights
Aboriginal and treaty rights are important considerations for moose management in Ontario.
Moose hold cultural significance for many Aboriginal peoples and continue to be an important traditional food source as well. Many Aboriginal communities in Ontario hold Aboriginal and treaty rights to harvest moose for food, social and ceremonial purposes. These harvesting rights generally apply within an Aboriginal community’s specific treaty area or recognized traditional harvesting area.
Aboriginal and treaty rights are recognized in section 35 of Canada’s Constitution Act, 1982. The courts have clarified that, after conservation needs are met, existing Aboriginal and treaty harvesting rights take priority in resource allocation and management.
The ministry is working with Aboriginal groups and communities to gain a better understanding of Aboriginal moose harvest, and ways we can work together to achieve common interests with respect to moose.
Moose need habitat that provides them with sufficient food and cover. They need cover from predators and shelter from extreme summer and winter weather. Moose move between different types of habitat throughout the seasons to best meet these needs.
Moose numbers are often highest in parts of the forest disturbed by fire or forestry. Fire and forestry promote the growth of young trees and shrubs, which provide nutritional food for moose.
Moose also require more mature vegetation. It provides the shelter that moose need in summer and winter.
Moose also need mineral licks, calving sites and aquatic feeding areas. These localized habitat features are very important for moose.
Moose numbers will decline if one or more key habitat components is lacking. Ideal moose habitat for browsing is forests aged about 5-30 years, and includes a mixture of young and mature forest.
Moose habitat is mainly managed through forest management on Crown land in Ontario.
The aims of forest management planning include:
- ensuring the overall quantity and quality of moose habitat reflects the range of natural variation in Ontario
- protecting the specific habitat features that benefit moose
Forest managers follow guides that give direction on creating and maintaining moose habitat:
- Forest Management Guide for Great Lakes-St. Lawrence Landscapes
- Forest Management Guide for Boreal Landscapes
- Forest Management Guide for Conserving Biodiversity at the Stand and Site Scales, which aims to conserve forest biodiversity so Ontario’s forests remain healthy and sustainable and protects important areas of moose habitat at the local scale, including winter cover, summer cover and aquatic feeding areas
- Ontario’s Cervid Ecological Framework, which provides landscape-level habitat management guidance for the province’s cervid species (caribou, elk, moose and white-tailed deer), to be considered when developing forest management plans
Under this approach:
- forestry seeks to preserve the natural variation in young, middle-aged, old, hardwood, conifer, and mixed-wood forest types
- patches of disturbance produced through forest harvest and other human activity are planned to emulate patches that are created by natural disturbances such as wildfire
This is done to ensure suitable habitat is available for a range of species, including moose, across the broader landscape.
What we’re doing
In general, habitat is not likely a limiting factor for moose in Ontario at the population levels at which they have existed historically. However, it can affect the success and health of moose populations at smaller scales across the province. Ontario’s approach to moose habitat management:
- recognizes the large scale pressures that influence wildlife, such as climate change
- allows for an ecosystem approach to managing interacting species
- ensures that the needs of individual species, including moose, are met locally
Parasites and disease
While no known diseases have a major impact on moose abundance in Ontario, several parasites can contribute to declining moose numbers. Of these, brain worm and winter tick are the main concerns. Other parasites, such as liver fluke, also occur in Ontario, but are not known to affect moose numbers.
Brain worm is a roundworm normally found in the brain of white-tailed deer. It is common throughout eastern North America. Animals such as deer and moose become infected when they accidentally eat snails or slugs infected with brain worm larvae while feeding on vegetation.
Deer are unaffected by brain worm infections, but in moose, these infections are usually fatal. Declines in moose populations possibly related to brain worm have been reported in northwestern Ontario, southeastern Manitoba, northwestern Minnesota, North Dakota, Michigan and Nova Scotia.
Signs of brain worm infections in moose vary but can include:
- toe-dragging or stumbling, disoriented behaviour, walking in circles
- extreme weakness
- loss of fear of humans
- weight loss
- remaining in a small area for an extended period of time
- inability to stand up
All ages of moose can be infected, but younger animals are generally affected more. In adults, brain worm is more common in females than males.
Winter ticks are a concern to moose in several parts of their range within eastern North America. Moose, along with elk and white-tailed deer are the primary hosts of winter ticks. In Ontario, the highest number of ticks found on a moose was 83,000, but the average is closer to 3,800.
Winter ticks affect the moose population because they:
- feed on moose during the winter (heavily infested moose must replenish a significant amount of blood)
- cause moderate to severe hair loss during the winter and early spring
These effects can kill moose, especially during March to April, as energy supplies dwindle at the end of winter and the potential for hypothermia rises in spring.
Liver flukes are a large flatworm whose primary host is white-tailed deer, although moose can also be infected. In Ontario, liver flukes are mostly found around the upper Great Lakes. They are limited to areas with certain types of snails that act as intermediate hosts.
Liver flukes are transmitted when moose accidentally consume freshwater snails along with vegetation. Liver flukes rarely infect young moose and are most common in middle-aged animals.
While no direct evidence shows that liver flukes kill moose, some biologists believe that highly infested moose may be more susceptible to other causes of death.
Other parasites and disease
Other parasites and diseases that may infect moose are not known to cause declines in moose populations. These include skin tumours or warts, and hydatid cysts and moose measles (both of which are larval tapeworms). Skin tumours or warts are caused by a skin virus that does not affect humans or the edibility of moose meat. Hydatid cysts, the larval stage of tapeworms, are commonly found in wolves. The tapeworm eggs (deposited through wolf feces) are accidentally ingested by moose along with vegetation. These tapeworms have no direct effect on moose. Moose are not known to have any parasites or diseases that can be directly transmitted to humans. Hunters are reminded that proper handling and preparation of wild game meat helps ensure food safety and quality.
Wolves and coyotes and hybrids of these species are found in Ontario. Gray wolves and gray wolf hybrids are found in both the northwest and northeast areas of Ontario and are the most effective at preying on moose. The number of gray wolves and their hybrids varies across the province but has been relatively stable overall for some time.
Relationship between moose, deer and wolf populations
Higher populations of prey species, such as moose and deer, can support higher populations of wolves. Predation rates on moose by wolves tend to increase in tandem with moose numbers. This naturally regulates the density of the moose population and is ultimately beneficial to moose and the ecosystems they rely on.
At very high densities, moose populations can degrade their own habitat, and experience increased occurrences of parasites such as winter ticks. Moose with brain worm or high numbers of winter ticks may be easier wolf prey in late winter.
Differences in wolf predation across Ontario
The ministry studied moose predation in northwest and central Ontario by placing radio and GPS collars on moose. The results show wide variation in the rate of wolf predation by area and wolf pack size.
Wolves were estimated to have caused half of the adult moose deaths recorded during the study in Ontario’s northwest. In comparison, wolves caused relatively few moose deaths in the Algonquin Provincial Park area in central Ontario. Outside of Algonquin, where wolf populations were lower, hunting and other natural factors caused more moose deaths.
The diet of wolves has also been studied in northwestern and northeastern Ontario by collecting scats (droppings) and analyzing their contents. In northeast Ontario, where moose density and calf numbers were low, moose was the primary prey of wolves during winter, but beaver was the most common prey consumed during the remainder of the year. In contrast, studies in northwestern Ontario and southwestern Quebec have shown moose remain an important food item for wolves throughout the year in those areas.
Wolf predation and wolf pack sizes
Wolf packs in Ontario are usually quite small, although packs as large as 19 wolves have been documented. Pack size and the number of packs in an area vary across Ontario, depending on the amount of prey available. Farther north, where prey abundance is lower, wolf territories don’t cover the entire landscape and some moose are able to live in areas with few or no wolves.
Generally, the number of moose killed by wolves increases with moose density and the number of moose living within wolf territories. Larger wolf packs kill more moose than smaller packs. But the increase in moose killed over time is not proportional to the increase in pack size. So, larger wolf packs actually kill fewer moose per wolf than smaller packs.
Wolf predation and hunting
Generally, wolves prey mostly on young moose and older moose past their prime, and consume few prime-breeding-age moose. However, moose populations in areas that are the most heavily hunted tend to include fewer calves and older moose. As a result, wolves prey on more prime-breeding-age moose during the winter months in these areas. This results in overall higher mortality of moose and may reduce moose population growth.
Wolf predation and roads
Ontario research has found wolves move at a higher rate on roads. These higher travel rates, in turn, lead to more encounters with moose. As a result, more moose are killed by wolves in areas that are closer to roads.
Results of wolf removal
The number of moose killed per wolf pack will not significantly decrease as the pack size is reduced, so removing just a few wolves from each pack will not decrease overall predation on moose. Only the removal of an entire pack can substantially reduce predation but this practice may not be ecologically or socially desirable. Changing hunting and trapping regulations to allow more wolves to be harvested is unlikely to remove an entire pack. Pack removal often requires intensive removal techniques such as aerial gunning or poisoning applied over several years. Only in limited circumstances may small reductions in pack size result in minor reductions in predation that benefit moose populations in localized areas.
Some provinces and states have undertaken wolf control efforts. After control measures were discontinued, wolf populations in Alaska, British Columbia, Quebec and Yukon soon recovered to pre-control levels. For example, in the Papineau-Labelle Wildlife Reserve in Quebec, wolf numbers recovered to previous levels less than a year after a 71% reduction in wolf numbers. Once wolf populations recover, moose populations typically return to pre-control levels.
The Strategy for Wolf Conservation in Ontario directs wolf management in the province. The goal of wolf management is to ensure ecologically sustainable wolf populations and the ecosystems on which they rely for the continuous ecological, social, cultural and economic benefit of the people of Ontario. Achieving this goal requires the consideration of both ecological and social values and interests.
Black bears, a predator of moose, inhabit most of Ontario’s forested area. Their range covers almost 90% of the province, from Lake Ontario northward to parts of the Hudson Bay Lowlands.
In 2010, it was estimated that there were 85,000-105,000 bears in the province.
Researchers compared moose calf survival in Algonquin Provincial Park and in nearby Wildlife Management Unit 49. This research looked at the importance of predation, among other factors, on moose calf mortality. Bear population densities were similar inside and outside the park. But, because bear hunting is only permitted outside the park, the makeup of the bear population may differ between the two areas. Predation by both bears and wolves was one of the most important causes of death for moose calves inside the park. Outside the park, hunting and other natural causes were much higher calf mortality factors. The higher numbers of adult male bears found in the park may account for the higher rates of moose calf predation, since male bears may be more effective predators of moose calves than female bears.
Studies in Quebec and Alaska
Research has been completed on the interaction between moose and bears in several other jurisdictions. These studies provide insights into moose-bear interactions that are relevant to Ontario.
In Quebec, black bears were largely opportunistic predators of moose calves, and often encountered calves incidentally while moving through their preferred habitat. Extensive movements by bears can lead to more encounters with moose calves. Studies from Alaska have shown that black bears may be a significant cause of death for moose calves during spring and summer.
Impact on moose
Most studies have shown that some black bears prey on calf moose that are less than two months of age. (In contrast, wolves prey on moose throughout the year, mainly targeting young moose and moose that are past their prime breeding age). These studies show that rates of black bear predation on moose calves vary a great deal, depending on ecosystem, habitat and landscape conditions. In a robust moose population, even high levels of predation by black bear on moose calves may not affect moose population growth. But a moose population that has been affected by other factors may be more sensitive to the impact of bear predation on calves.
Results of bear removal
Several studies have looked at the effect of black bear removal on moose populations. The results of these studies can be difficult to interpret because of the complex ecological relationships in landscapes that have multiple predator and prey species. It can also be difficult to rule out other factors that may be affecting moose, such as habitat changes.
Bear removal research has generally shown that:
- low density moose populations may benefit in an area in the short-term
- moderate or high density moose populations may not benefit
- any benefits to moose are short-lived as bears recover quickly once removal ends (as bears from surrounding areas move into the area where removal occurred)
Ontario’s approach to managing black bear is outlined in the Framework for Enhanced Black Bear Management in Ontario. The goal of black bear management is to ensure sustainable black bear populations across the landscape and the ecosystems on which they rely for the continuous provision of ecological, cultural, and optimal economic and social benefits for the people of Ontario.
Climate change could dramatically alter Ontario’s ecosystems by changing temperature and precipitation. Moose may be affected by these changes in the following ways.
Moose are adapted to extreme cold and deep snow conditions. But they become stressed when summer or winter temperatures rise above a certain threshold.
Since 1997, in the boreal forest of northeastern Canada:
- at least 10 winters have had warmer than normal temperatures
- at least 12 winters have had less than normal precipitation
Decreased reproductive fitness
Moose feeding is reduced in long periods of high temperatures. This lowers the fat reserves that moose need for winter. This reduction in fat reserves could result in an inadequate quality or quantity of milk for calves. Calves with too little milk or poor quality milk will have poor body condition for winter and may have increased risk of dying.
Warmer and more variable early fall temperatures could lower calf production by causing:
- a delay in breeding, which could result in higher hunter success and overharvest
- a mismatch in the breeding period for bulls and cows, which could reduce the number of cows that are bred
Warmer temperatures, particularly in mild fall and early spring conditions, can result in increased tick infestation on moose.
Increased numbers of white-tailed deer
White-tailed deer can more easily survive winter when less snow falls. A larger white-tailed deer population could:
- increase the number of wolves, which prey on both deer and moose
- transmit the parasites brain worm and liver fluke to moose at a higher rate
Changes in moose habitat quality
Changes in climate can affect the quality of moose habitat. This can change the geographic distribution of moose, as habitat becomes more or less suitable.
Warmer temperatures and reduced precipitation in summer can also increase the fire hazard. This may significantly increase moose habitat in some areas.
Increased fire frequency is expected to benefit moose by creating early successional forest habitat, or new growth, which provides good food for moose. This is one of the habitats important to moose.
Potential future effects
Ontario has studied how climate change could affect habitat and species in the future. These studies use predicted seasonal temperatures and precipitation. They help to forecast the health of species, including moose. These forecasts can assist with moose management planning.
The predictions vary, by the time scale and climate change scenario used.
One forecast suggests that, by the year 2040, moose numbers will begin to decline in southern Ontario, but increase in parts of the northwest and northeast.
What we’re doing
Ongoing research will:
- improve our understanding of how climate change will affect moose
- help to identify the key factors influencing the size of Ontario’s moose population
- guide moose management in the province
Ongoing monitoring will:
- track moose population trends
- support our adaptive and responsive approach to moose management