Northern Leopard Frog
Western Boreal/Prairie populations

Description
The Northern Leopard Frog is a medium-sized frog characterized by conspicuous dark dorsal spots bordered by light-coloured rings. It has a whitish belly and prominent light-coloured, dorsolateral folds. Its dorsal background colour is commonly green, but may be brown. Adults range from 50 to 100 mm in length from snout to vent. Females are larger than males, but males have larger forelimbs.

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Approximate range - not for legal use

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Distribution and Population
In Manitoba, the species was formerly abundant along the southern shores of Lake Winnipeg and Lake Manitoba, and less common up to Southern Indian Lake and east of Lake Winnipeg. By 1976 Leopard Frogs had been virtually extirpated from the province. The species has reoccupied much of its historic range, although densities are far below previous levels.

In Saskatchewan, the species once ranged across the province south of about 55°N. Populations in this province have greatly declined since the late 1970s. The species is still widespread but populations tend to be isolated. The population status of the frog has been tentatively labeled "secure" in Saskatchewan.

In Alberta, the Northern Leopard Frog ranged widely south of 55°N, except in the mountains of the west. Records are also known from north of 55°N. By 1979, the species had vanished from most of its range in Alberta. Only 26 of 74 known breeding populations remain, with breeding confirmed in only 12 of these; the majority at these 12 are in the southeastern corner of the province.

The species has a limited distribution in the Northwest Territories, ranging between the Alberta border and Great Slave Lake. The frog has been reported recently in three of the nine known sites.

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Habitat
A typical breeding site for this species is a temporary pond about 30-60 m in diameter, 1.5-2.0 m deep, located in an open area, and lacking fish. The presence of significant vegetation seems to be important. In the summer frogs are found in a variety of habitats, but usually not in heavily treed areas, in grass that is more than a meter tall, or in open sandy areas. Preferred habitat seem to be in vegetation 15-30 cm tall. Well-oxygenated water bodies that do not freeze solid are preferred for overwintering.

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Biology
Northern Leopard Frogs emerge from overwintering ponds when the water temperature rises to 7-10°C; they then migrate to breeding ponds. A female mates only once and lays a single egg mass, which is attached to submerged vegetation or laid at the surface. Individual females commonly lay around 3500 eggs. Hatching success is generally high. Tadpoles (larvae) can hatch in 9 days or less; after 2 or 3 days the tadpoles become free-swimming. Tadpoles are aquatic, primarily herbivorous, and few survive the summer. At 20°C, it takes them around 90 days to grow to sexual maturity (become semi-aquatic frogs). The frogs typically spend more than 95% of the day sitting in a small clearing of damp soil in leaf litter. In overcast, rainy conditions they hunt for moving prey of accessible size, mostly arthropods. In the fall they move to overwintering sites. They hibernate in small circular excavations in the surface of the mud. The mortality rate of the adults is about 60%.

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Threats
The destruction or modification of the species’ breeding, summer or overwintering habitat, or a change which prevents the frogs from moving from one habitat type to another, can eliminate a population. Habitat can also be modified negatively by the introduction of alien animals or plants, such as Common Carp and Purple Loosestrife. In Manitoba, the impact of commercial harvests, especially in the early 1970s, may have contributed to the decline. In Saskatchewan, a long drought as well as wetland modifications were highlighted as factors negatively influencing the species. In Alberta, "red leg", a condition associated with a bacterial infection and renal failure, was believed to be the cause of high mortality in 1976. However, "red leg" appears to become more prevalent when stress levels due to other causes have become higher.

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Protection
Species that have been designated at risk by COSEWIC since the Species at Risk Act (SARA) was written must be added to Schedule 1 through a regulatory amendment. Information on this procedure, including the public consultation process, is available on the SARA Public Registry. If Northern Leopard Frog Western Boreal/Prairie populations is added to Schedule 1, it will benefit from the protections afforded by SARA. More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

In Manitoba, the frog occurs in Riding Mountain National Park, as well as provincial parks, wildlife management areas and other refuges. The Manitoba Wildlife Act stipulates that a permit is required to collect the species, specifies the collecting season, and sets the maximum harvest at 50 tons of adults per year. In Saskatchewan, the species occurs within Grasslands National Park. However it is not legally protected in the province and no permit is required to collect it. In Alberta, the government designated the Northern Leopard Frog as endangered in 1987. The habitat of a few populations are also protected by their occurrence in parks and protected areas. In the Northwest Territories, the species can be captured or killed for management or research with a permit.

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References
- Bishop, C.A., and K.E. Pettit (Eds.). 1991. Declines in Canadian amphibian populations: designing a national monitoring strategy. Occasional Paper No. 76, Canadian Wildlife Service, Ottawa. 120 pp.
- Green, D.M. 1998. Scientists seek causes of amphibian decline. In: Recovery: An Endangered Species Newsletter. Canadian Wildlife Service, Ottawa. Fall 1998. Pages 1 and 3.
- Seburn, C.N. L. 1998. COSEWIC Status Report on the NORTHERN LEOPARD FROG Rana pipiens. Committee on the Status of Endangered Wildlife in Canada. 43 pp.

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