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| Status of amphibian and reptile populations in Canada |
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Canada is home to 45 species of amphibians and 46 species of reptiles (see Appendix 1 for an overview of amphibians and reptiles in Canada).
What is happening to amphibian and reptile populations?
Populations of both amphibians and reptiles are declining in Canada.
The Canadian Endangered Species Conservation Council, in its report Wild Species 2000, provided a provincial/territorial assessment of the general status of wildlife in Canada, including amphibians and reptiles.
Amphibians
Populations of 16 of Canada's 45 amphibian species (36%) have declined to the extent that they have been designated as endangered, threatened, or of special concern (see Box and Appendix 2).
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) classification categories:
Extirpated: a species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered: facing imminent extirpation or extinction.
Threatened: likely to become endangered if limiting factors are not reversed.
Special concern: certain characteristics make it particularly sensitive to human activities or natural events.
Harvests of Manitoba's population of the Northern Leopard Frog traditionally had made up a large portion of the North American market (Table 1). By 1976, the species had virtually disappeared from the province, and no exports were made. Numbers partially recovered, but as of 2000 have not approached early 1970s levels.
Reptiles
Populations of 21 of Canada's 46 reptile species (46%) are at risk (Appendix 2). The Pygmy Short-horned Lizard and the Timber Rattlesnake are listed as extirpated.
Why are there concerns about declines in amphibian and reptile populations?
As indicators of environmental health, declines in amphibian and reptile populations and the disappearance of species are worrisome signs of local to global environmental problems that may also pose threats to other species, including humans.
What is causing declines in amphibian and reptile populations?
Often multiple factors are involved. The following are some examples of stresses faced by Canada's amphibian and reptile populations.
Habitat loss, degradation, and fragmentation: Wetlands are particularly important habitats for most Canadian amphibians and many reptiles. However, wetland loss is a common problem across Canada. On the prairies, about 70% of historic wetlands have been drained, mostly for agriculture. In southern Ontario, over 90% of wetlands have been lost. Amphibian and reptile populations have suffered the consequences of such losses of habitat.
Even when good habitats remain, however, habitat fragmentation (see Box) can also cause population isolation and declines. If the remaining ponds in a landscape are isolated or the land between ponds is inhospitable, amphibians fleeing a drained wetland might not make it to the next available patch of suitable habitat (e.g., see Photo below).
Habitat fragmentation and traffic mortality
On warm, rainy nights in the spring, many amphibians migrate from overwintering sites to breeding ponds. If a road separates these two habitats, many migrating animals may be run over.
Similarly, thousands of reptiles are killed every year on roads and highways. Many snakes are drawn to roads in the evenings because the dark surface is warmer than the surrounding landscape, but the problem is particularly bad when large snake hibernation quarters are separated from the snakes' summer range by a road.
Environmental pollution: Some amphibians can survive in agricultural areas. They may enjoy the benefits of artificial ponds created for irrigation or for watering. However, the use of pesticides, fertilizers, and other agricultural chemicals poses a documented threat. In Quebec, grossly deformed frogs have been found in areas where pesticide use is especially heavy.
Amphibians, particularly in the larval stage, may also be at risk from fertilizer application to agricultural fields. A 1999 publication reported that of 8 545 water samples collected from watersheds in states and provinces bordering the Great Lakes, 19.8% contained nitrate concentrations exceeding those that can cause developmental anomalies and other sublethal effects in amphibians, and 3% were high enough to kill amphibians.
Reptiles are high up in the food web and, as a result, often contain very high levels of polychlorinated biphenyls (PCBs), dioxins and furans, and other persistent toxic chemicals, which they accumulate and concentrate from the prey that they consume. Females often transfer these contaminants to their eggs. In the Great Lakes basin, up to 40% of eggs of Common Snapping Turtles in some areas either do not hatch or contain deformed young.
Endocrine-disrupting compounds are chemical contaminants that mimic natural hormones and may cause subtle, sublethal effects. For example, some chemicals mimic the female hormone estrogen and prevent juvenile males from properly maturing.
Acidic deposition: Amphibians are especially susceptible to acidification, because many of them rely on ponds for reproduction. It is generally in the spring that ponds are the most acidic, due to the melting of "acid snow." Many Canadian amphibians lay their eggs as soon as ice comes off the ponds in the spring. Acidic deposition may also impact the food supply of amphibians. Adult frogs can survive in waters that are fairly acidic (i.e., pH as low as 4.0), but some of the food that they eat, such as insects, cannot survive at low pH levels.
Ultraviolet (UV) radiation: Eggs of some amphibian species are susceptible to increases in UV radiation, particularly species that lay eggs near the water surface. The effects may be most serious when exposure to UV radiation occurs together with other stressors.
Climate change: Amphibians are very dependent on the weather, particularly for the survival of their eggs and larvae, and reptiles have temperature-dependent sex determination. Dramatic changes in climate could eliminate some species from large areas. For example, increased drought across the prairies could prevent many species from transforming before ponds dry up each year.
Diseases: Some viruses and fungi pose significant threats to amphibians and reptiles. For example, amphibian larvae appear to be highly susceptible to iridoviruses, and mortality can be extremely high. The Regina ranavirus (a type of iridovirus) caused die-offs of Tiger Salamanders from southern Saskatchewan in 1997 and 1998.
What is being done about the problem?
The Species at Risk Act (SARA) is a key federal government commitment to prevent wildlife species from becoming extinct and secure the necessary actions for their recovery. It provides for the legal protection of wildlife species and the conservation of their biological diversity.
The federal government, provincial/territorial governments, nongovernmental organizations, and universities/academics have teamed up to establish a national recovery program for species at risk. The Recovery of Nationally Endangered Wildlife (RENEW) program provides for the development of recovery plans for species at risk. Recovery plans have been initiated for three amphibians and six reptiles.
The Canadian Amphibian and Reptile Conservation Network (CARCNET) is a network of biologists and other interested people who study, protect, and educate people about amphibians and reptiles. It also helps coordinate public involvement in frog and toad monitoring programs across Canada. A major CARCNET initiative is the development of a system to designate Important Amphibian and Reptile Areas in Canada to raise awareness about the habitat required to support these animals.
Frogwatch is a volunteer monitoring program coordinated by the Ecological Monitoring and Assessment Network (EMAN). It collects information on the range and distribution of frog species across Canada.
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