Wild species 2010: chapter 22


Amphibia - The class of vertebrate chordates that contains the frogs, toads, newts and salamanders. The amphibians evolved in the Devonian period (about 370 million years ago) as the first vertebrates to occupy the land, and many of their characteristics are adaptations to terrestrial life.

Photo of a Great Plains Toad
Photo: Great Plains Toad, Anaxyrus cognatus © Erik Enderson

Quick facts

  • There are roughly 5700 species of amphibians worldwide, 47 of which are found in Canada.
  • When excluding species ranked as Extinct, Extirpated, Undetermined, Not Assessed, Exotic or Accidental, more than two-thirds (67%) of amphibian species have Canada General Status Ranks (Canada ranks) of Secure, but 20% have Canada ranks of At Risk and 13% have Canada ranks of Sensitive. No amphibians have Canada ranks of May Be At Risk.
  • Since Wild Species 2005, the Barred Tiger Salamander (Ambystoma mavortium) has been declared a separate species from the Eastern Tiger Salamander (Ambystoma tigrinum), increasing the total number of amphibian species in Canada to 47.
  • On a global scale, many amphibian species are at a high level of risk of extinction; a recent Global Amphibian Assessment ranked nearly one-third (32%) of the world’s amphibians as Threatened, compared with 23% of all mammal species and 12% of all bird species.
  • The Wood Frog (Lithobates sylvaticus) has the most northerly distribution of any North American amphibian, and is the only North American amphibian found north of the Arctic Circle.


Canadian amphibians include frogs, toads, newts and salamanders. These cold-blooded vertebrates can be recognized by their soft, moist skin, without scales, feathers or fur. Many amphibians spend the first part of their life cycle as aquatic, gill-breathing larvae (also known as tadpoles) before they metamorphose into terrestrial, air-breathing adults. This dual life cycle allowed ancestral amphibians to be the first vertebrates to inhabit dry land more than 300 million years ago, giving rise to the modern amphibians, reptiles, birds and mammals.

Many people are familiar with the typical life cycle of frogs and toads, in which an aquatic larva with gills metamorphoses into a terrestrial air-breathing adult. However, in the process of adapting to a wide range of habitats, amphibians have developed a variety of different life cycles, ranging from completely aquatic (e.g. Mudpuppy, Necturus maculosus), to completely terrestrial. For example, the Northern Red-backed Salamander (Plethodon cinereus) lays its eggs on land and guards them until they hatch into juveniles, which look and behave much like the adults. Newts, such as the Roughskin Newt (Taricha granulosa) of British Columbia, have an additional stage in their life cycle, known as the eft. Aquatic larvae with gills metamorphose into terrestrial air-breathing efts, which live up to four years in moist terrestrial habitats. Efts must then metamorphose into amphibious adults to breed and complete the life cycle. The amazing diversity of life cycles displayed by amphibians is not matched in any other group of vertebrates.

Unlike reptiles, birds and mammals, adult amphibians do not have waterproof skin. This is advantageous for amphibians because it allows them to breathe through their skin as well as through their lungs, but it makes amphibians prone to dehydration. So how do amphibians survive on dry land? Many amphibians have special skin on their underside through which they can absorb moisture. This allows them to re-hydrate simply by sitting on moist soil or in a small puddle. To reduce water loss, many amphibians are nocturnal. During the day they remain under logs and rocks. At night, when the air is cooler and less evaporation occurs, they emerge to hunt for food or mates. These physical and behavioural adaptations allow amphibians to survive away from the water, where they can take advantage of many different habitats and food sources.

Like reptiles, amphibians are cold-blooded (ectothermic), meaning they rely on external heat sources (like the sun) to warm their body, rather than producing heat from food energy, like birds and mammals. However, amphibians can survive much further north than reptiles. The distribution of amphibians in northern habitats is largely related to winter temperature and the ability of individual species to tolerate cold. The champion of cold-tolerant amphibians is the Wood Frog (Lithobates sylvaticus), the only North American amphibian or reptile found north of the Arctic Circle. Wood Frogs survive cold temperatures by hibernating frozen underground for several months of the year. Normally cells rupture and die when they are frozen, but Wood Frogs produce a special “anti-freeze” chemical called a cryoprotectant that protects their cells when frozen solid! Cryoprotectants are of great interest to scientists, who have studied Wood Frogs to develop new methods of freezing mammalian organs, so they can be stored before transplantation.

Status of knowledge

People have been studying amphibians for centuries, so the basic biology, physiology and developmental biology of many species, particularly the frogs, is well known. The natural history of most amphibians in Canada is also generally well understood, but the distribution, population size and population structure of amphibians in some regions is not well known. This is partly due to the difficulties in monitoring amphibians which can include their nocturnal and secretive behaviours, their small size and their cryptic appearance. Initiatives such as “Frogwatch”, a program that uses volunteers to monitor amphibian populations across the country, are providing data which will increase our understanding of amphibian distributions, and provide baseline data to monitor population changes.

Genetic tools are becoming increasingly important in amphibian research. For example, in 1997, genetic analysis was used to distinguish the Oregon Spotted Frog (Rana pretiosa) as a separate species from the Columbia Spotted Frog (Rana luteiventris). Genetic tools have also been used to study American Bullfrog (Lithobates catesbeianus) dispersal in Ontario, the impact of clear-cutting on the Coastal Giant Salamander (Dicamptodon tenebrosus) in British Columbia and the evolution of new species of salamanders (speciation) in the Rocky Mountains.

In recent years, the impacts of environmental contaminants on the growth and development of amphibians has been studied across Canada. Chemicals and fertilizers, which collect in some aquatic habitats used by amphibians, can cause a range of negative effects including deformities, reduced immune system activity, abnormal behaviours and, in extreme cases, death. However, it is difficult to link these impacts with population declines.

Richness and diversity in Canada

Canada has 47 species of amphibians including one mudpuppy, two newts, seven toads, 18 frogs and 19 salamanders. The most species rich provinces are Ontario (26 species), British Columbia (22 species) and Quebec (21 species) (figure 22). British Columbia has the most species found nowhere else in Canada (13 species). All the amphibian species found in Canada are also found in the USA, but several species including the Canadian Toad (Anaxyrus hemiophrys) and the Mink Frog (Lithobates septentrionalis), have the majority of their range in Canada.

Species spotlight - Northern Leopard Frog

Northern Leopard Frogs, Lithobates pipiens, (Canada General Status Rank (Canada rank): Secure) are found in every province and territory except the Yukon. This medium-sized frog breeds in shallow, warm ponds and produces egg masses of 600 to 7000 eggs. Eggs hatch into tadpoles, which graze on algae for about 9 to 12 weeks, until they are ready to metamorphose into adults.

Adults spend the summer feeding away from the water, but return to deep, well-oxygenated water to hibernate.

Northern Leopard Frogs were once common throughout their Canadian range, but during the late 1970s they underwent rapid, widespread population declines in British Columbia, Alberta, Saskatchewan, and Manitoba. In fact, Northern Leopard Frogs had virtually disappeared from Manitoba by 1976 and from Alberta by 1979. Lack of monitoring before this period makes population trends difficult to interpret, and scientists are still uncertain of the reason for the declines. Since the 1980s, Northern Leopard Frog populations in Alberta and Saskatchewan have been recovering slowly, whereas Manitoba’s populations have recovered relatively quickly. In British Columbia, populations have not substantially recovered and are now restricted to a single Wildlife Management Area.

The story of the Northern Leopard Frog demonstrates that even widespread, numerous species are vulnerable to catastrophic population declines and local extirpation. Scientists are now focusing on captive breeding and release in Alberta and British Columbia and population monitoring in Alberta and Saskatchewan to attempt to restore this species to its former range and to improve our knowledge of the Northern Leopard Frog.

Photo of a Northern Leopard Frog
Photo: Northern Leopard Frog, Lithobates pipiens © Erik Enderson

Species spotlight - Oregon Spotted Frog

The Oregon Spotted Frog, Rana pretiosa, was described as a distinct species, separate from the Columbia Spotted Frog, in 1997. In the same year, the Oregon Spotted Frog was the first species to be given an emergency listing of Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). This small frog was once distributed from southwest British Columbia to northwest California, but is now restricted to small, isolated populations and is estimated to have been lost from more than 90% of its historic range. Population declines and range reduction have been linked to habitat loss, changes in hydrology, introduction of exotic predators and vegetation, and isolation of remaining populations. In addition, they are vulnerable to pollution and climate change. Now known from only three populations in southwest British Columbia and less than 30 populations in the United States, this species has a Canada rank of At Risk, and an IUCN Red List rank of Vulnerable, meaning it is considered vulnerable to extinction on a global scale.

Since the emergency designation by COSEWIC, work has begun on a recovery plan for the Oregon Spotted Frog with the co-operation of government agencies, universities, local native groups and the public. Captive breeding, habitat mapping and habitat remediation have already begun. Although the three small remaining Canadian populations are isolated from each other and from populations in the United States, the development of the recovery plan and the co- operation between different agencies and groups gives hope that this species can be preserved into the future.

Species spotlight - Western Toad

The Western Toad, Anaxyrus boreas, is the only toad found in the Yukon, and it is also found in the Northwest Territories, British Columbia and Alberta. This large toad breeds in the shallow margins of ponds, streams and lakes. Females can produce clutches of up to 15 000 eggs, but may breed only once in their lifetime. Adult toads frequently wander long distances from water and are usually nocturnal, especially at low elevations. In the winter, Western Toads hibernate in animal burrows or under loose debris. Adult Western Toads are carnivorous and eat a wide range of invertebrates including earthworms, beetles, spiders and ants. Despite their ability to release a mild poison, Western Toads are preyed on by reptiles, mammals and birds.

Due to a COSEWIC status assessment (Special Concern in 2002), the Canada rank of the Western Toad changed from Secure in Wild Species 2000 to Sensitive in Wild Species 2005. The Canada rank remains Sensitive in this report. The 2002 COSEWIC status assessment found this species of special concern, due to evidence of population declines and at least one example of a local extirpation. Canadian populations of Western Toads are not only a unique component of the fauna of western Canada, they are also important to the global survival of this species, due to declining populations in the United States. Careful monitoring and research are needed to help maintain healthy Canadian populations of Western Toads.

Results of general status assessment

Of the 47 species of amphibians found in Canada, nine species (19%) have Canada ranks of At Risk (figure 22). Within Canada, all nine species with Canada ranks of At Risk have fairly restricted ranges. None are found in the territories, and only one, the Allegheny Mountain Dusky Salamander (Desmognathus ochrophaeus), is found in more than one province (Ontario and Quebec).

Six species of amphibian have Canada ranks of Sensitive (13%) and 31 species have Canada ranks of Secure (66%). Canada has no Exotic or Accidental amphibian species and no species have Canada ranks of May Be At Risk, Undetermined or Not Assessed.

Figure 22. Results of the general status assessments for amphibian species in Canada in the Wild Species 2010 report.

bar graph (see long description below)

Long description for Figure 22

Figure 22 shows the results of the general status assessments for amphibian species in Canada in the Wild Species 2010 report. The bar graph shows the number of amphibian species ranked as Extinct, Extirpated, At Risk, May Be At Risk, Sensitive, Secure, Undetermined, Not assessed, Exotic, and Accidental in Canada, each province and territory and the 4 oceanic regions. Of the 47 species occurring in Canada, 1 was ranked as Extirpated, 9 as At Risk, 6 as Sensitive and 31 as Secure. Of the 4 species occurring in the Yukon, 2 were ranked as May Be at Risk, 1 as Sensitive and 1 as Secure. Of the 5 species occurring in the Northwest Territories, 2 were ranked as May Be at Risk, 1 as Sensitive and 2 as Secure. Of the 8 species occurring in Nunavut, 2 were ranked as Undetermined and 6 as Not Assessed. Of the 22 species assessed in British Columbia, 6 were ranked as At Risk, 3 as Sensitive, 11 as Secure and 2 as Exotic. Of the 10 species occurring in Alberta, 1 was ranked as At Risk, 3 as May Be at Risk, 3 as Sensitive and 3 as Secure. Of the 7 species occurring in Saskatchewan, 2 were ranked as At Risk, 1 as Sensitive and 4 as Secure. Of the 16 species occurring in Manitoba, 1 was ranked as At Risk, 2 as May Be at Risk, 3 as Sensitive, 9 as Secure and 1 as Undetermined. Of the 26 species occurring in Ontario, 2 were ranked as Extirpated, 6 as At Risk, 1 as Sensitive and 17 as Secure. Of the 21 species occurring in Quebec, 1 was ranked as At Risk, 4 as May Be at Risk, 2 as Sensitive and 14 as Secure. Of the 16 species occurring in New Brunswick, 1 was ranked Sensitive, 14 Secure and 1 Undetermined. All 13 species occurring in Nova Scotia were ranked as Secure. Of the 10 species occurring in Prince Edward Island, 1 was ranked as May Be at Risk and 9 as Secure. Of the 8 species occurring in Newfoundland and Labrador, 6 were ranked as Secure, 1 as Undetermined and 1 as Exotic. There were no species listed as occurring in the oceanic regions.

Comparison with previous Wild Species reports

Since the report Wild Species 2005, the Barred Tiger Salamander (Ambystoma mavortium) is no longer considered a subspecies of the Eastern Tiger Salamander (Ambystoma tigrinum) and both salamanders are now treated as full species. This raised the total number of amphibians in Canada from 46 to 47 (table 30) and led to a Canada rank of Extirpated being assigned to the Eastern Tiger Salamander (based on 2001 COSEWIC assessment).

A total of three species had a change in their Canada rank since the last assessment. Among these changes, one species had an increased level of risk, one species had a reduced level of risk, and one species was added. The changes were due to taxonomic change and improved knowledge (table 31). None of the changes were due to biological changes in species abundance, distribution or threats.

Table 30. Changes in the number of amphibian species over time in each rank category as determined by the National General Status Working Group.
Canada rank Years of the
Wild Species reports 2000
Years of the
Wild Species reports 2005
Years of the
Wild Species reports 2010
Average change between reports Total change since first report
0 Extinct / Extirpated 0
+1 species +1 species
1 At Risk 4
+3 species +5 species
2 May Be At Risk 6
-3 species -6 species
3 Sensitive 6
Stable Stable
4 Secure 29
+1 species +2 species
5 Undetermined 0
Stable Stable
6 Not Assessed 0
Stable Stable
7 Exotic 0
Stable Stable
8 Accidental 0
Stable Stable
Total 45 (100%) 46
+1 species +2 species


Table 31. Reasons for changes in the status of amphibian species between the last assessment and the current report.
Scientific name English name 2005 Canada rank 2010 Canada rank Reason for change
Ambystoma mavortium Barred Tiger Salamander - 4 (T) Previously included in Ambystoma tigrinum (taxonomic change).
Ambystoma tigrinum Eastern Tiger Salamander 4 0.1 (T) Listed as Extirpated by COSEWIC in 2001. Previous General Status rank included subspecies mavortium, now treated as a full species.
Plethodon idahoensis Coeur d’Alene Salamander 3 4 (I) Improved knowledge of the species.

Threats to Canadian amphibians

Global amphibian declines over the last 20 years, have spurred considerable discussion of threats to amphibians. Major threats include habitat loss and degradation, introduction of exotic species, over-harvesting (for commercial and recreational use), increases in UV radiation, pollution, disease and climate change. In addition, road mortality is also a threat to some amphibian populations.

Habitat loss is one of the leading threats to amphibians in Canada. In parts of southern Canada, 90% of wetlands have been drained or otherwise destroyed. Remaining wetlands within agricultural or urban landscapes may be polluted and often retain a reduced abundance and diversity of amphibians. In addition, fragmentation of remaining habitat can reduce or prevent the movement of individuals between populations, leading to reduced population stability and reduced flow of genes between populations.

Fungal and viral diseases have been implicated in some global amphibian declines, even in pristine habitats. Research is showing that disease acts on populations in combination with other stresses. For example, incidence of disease may be increased in populations stressed by other factors such as pollutants or increased UV-B radiation.


This reassessment of Canada’s amphibians resulted in three Canada rank changes compared to Wild Species 2005. The changes resulted not from biological changes in species abundance, distribution or threats, but from taxonomic change, a COSEWIC assessment and improvements in our knowledge of Canadian amphibians.

Further information

AmphibiaWeb: Information on amphibian biology and conservation. (Accessed February 16, 2010).

Canadian Amphibian and Reptile Conservation Network [PDF, 302 KB]. (Accessed February 16, 2010).

Conant, R. and Collins, J. T. 1998. A field guide to reptiles and amphibians of eastern and central North America, third edition. Houghton Mifflin Co., Boston: 616 pp.

EMAN. 2004. Status of amphibian and reptile populations in Canada. (Accessed February 16, 2010).

Frogwatch. (Accessed February 16, 2010).

Froom, B. 1982. Amphibians of Canada. McClelland and Stewart, Toronto, Ontario: 120 pp.

IUCN, Conservation International, and NatureServe. 2004. Global amphibian assessment. Amphibian Red List Authority (Accessed February 16, 2010).

The Tree of Life. 1995. Living amphibians. (Accessed February 16, 2010).

Stebbins, R. C. and Cohen, N. W. 1995. A natural history of amphibians. Princeton University Press, Princeton, New Jersey: 316 pp.

Virtual exhibit on Canada’s biodiversity: focus amphibians. (Accessed 15 October 2005).


COSEWIC. 2000. COSEWIC assessment and status report on the Oregon spotted frog Rana pretiosa in Canada. (Accessed February 11, 2010).

COSEWIC. 2002. COSEWIC assessment and status report on the western toad Bufo boreas in Canada. (Accessed February 11, 2010).

COSEWIC. 2009. COSEWIC assessment and update status report on the northern leopard frog Lithobates pipiens(Southern Mountain population) in Canada. (Accessed February 11, 2010).

Fahrig, L., Pedlar, J. H., Pope, S. E., Taylor, P. D. and Wegner, J. F. 1995. Effect of road traffic on amphibian density. Biological Conservation 73: 177-182.

Green, D. M. (editor). 1997. Amphibians in decline, Canadian studies in a global problem. Herpetological Conservation 1: 1-338.

Gibbons, J. W., Scott, D. E., Ryan, T. J., Buhlmann, K. A., Tuberville, T. D., Metts, B. S., Greene, J. L., Mills, T., Leiden, Y., Poppy, S. and Winne, C. T. 2000. The global decline of reptiles, déjà vu amphibians. BioScience 50: 653-666.

Hine, R. S. and Martin, E. (editors). 2004. The dictionary of biology. Oxford University Press, Oxford, England: 698 pp.

Oldham, M. J. 1996. Amphibians and reptiles. In Assessment of species diversity in the mixedwood plains ecozone (I. M. Smith, editor). Ecological Monitoring and Assessment Network, Environment Canada. (Accessed October 15, 2005).

Ouellet, M., Bonin, J., Rodrigue, J., DesGranges, J. and Lair, S. 1997. Hindlimb deformities (ectromelia, ectrodactyly) in free-living anurans from agricultural habitats. Journal of Wildlife Diseases 33: 95-104.

Seburn, D. and Seburn, C. 2000. Conservation priorities for the amphibians and reptiles of Canada [PDF, 952.75 KB]. World Wildlife Fund Canada and the Canadian Amphibian and Reptile Conservation Network. Toronto: 92 pp. (Accessed October 15, 2005).

Storfer, A. 2003. Amphibian declines: future directions. Diversity and Distributions 9: 151-163.

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