Species of special interest


Amphibians are an integral part of aquatic food webs, feeding on algae and insects at different life stages and serving as food for a wide range of predators, including dragonflies, fish, snakes, and birds. They are particularly sensitive to pollutants absorbed through their skin, which makes them good indicators of wetland contamination and degradation.1

In the Great Lakes Basin, four amphibian species, American toad, western chorus frog, northern leopard frog, and green frog, may have declined since the mid-1990s. Spring peeper is the only species out of eight monitored that has been increasing. However, the timeline is too short to be certain that these are long-term trends and not part of natural variation.1 In the St. Lawrence River, 27% of amphibians and reptiles are at risk within the highly developed river corridor.2 The northern leopard frog is considered Threatened in Alberta, red-listed in B.C., and assessed as Endangered (Rocky Mountain population), Special Concern (Western Boreal/Prairie populations) or Not At Risk (Manitoba and eastern populations) by COSEWIC.3

Batrachochytrium dendrobatids (Bd), a chytrid fungus of the skin, has been implicated in worldwide amphibian declines4 (see Invasive Non-native Species). Ranaviruses have also been responsible for mass die-offs of amphibians worldwide.5 Canada’s Boreal Shield,6 Prairies,7 and Mixedwood Plains6, 8 ecozones+ have documented cases of ranaviruses.

Amphibians in the Great Lakes Basin
Annual occurrence index (percent of monitoring stations where the species was recorded), 1995 to 2007
Graphs: amphibians in the Great Lakes basin. Click for graphic description (new window). iStock.com photos: Western chorus frog © rmarnold; Northern leopard frog © maimai; Bullfrog © Valmol48; Gray treefrog © HKPNC. dreamstime.com photos: American toad © David Anderson Wetlands, Algonquin Provincial Park; Ontario © Elena Elisseeva; Spring peeper © Jason Ross; Wood frog © Mircea Costina; Green frog © Electrochris.
Source: Archer et al., 2009.1

Global Trends

As of 2004, 43% of amphibian populations were in decline and 33% of all amphibian species were globally threatened. The dominant causes of declines worldwide are habitat reduction (North America and Europe), over-exploitation (Asia), and unexplained causes, possibly linked to disease (South America, Australia, and New Zealand).9