Re-introduction of the northern leopard frog in British Columbia and Alberta, Canada

Summary

The northern leopard frog, Endangered in British Columbia's Rocky Mountain population and of Special Concern in Alberta's boreal/prairie populations, has been reintroduced at multiple sites across both provinces since the 1980s in response to declines from habitat loss, introduced fish and chytrid fungus. In BC, where the only sources are the Creston Valley Wildlife Management Area and a Vancouver Aquarium captive colony, phase-one releases at the Upper Kootenay Floodplain from 2003-2005 were followed by much larger annual translocations from 2011-2015 totaling roughly 34,000 tadpoles, while a newer Columbia Marshes site received around 5,600 tadpoles from both sources by 2015. In Alberta, nearly 35 years of reintroductions have used wild-collected eggs reared at outdoor ponds, releasing roughly 14,000 head-started young at Raven River and other sites between 1999-2004, 8,500 tadpoles at Magrath, and over 75,000 tadpoles at Waterton Lakes National Park between 2007-2010. Outcomes varied sharply by site: both BC Upper Kootenay phases and Alberta's Magrath site show sustained evidence of successful overwintering and breeding years after release, while some Alberta sites never confirmed frog presence, and others that initially thrived later collapsed or went unmonitored. Chytrid fungus was detected at several sites without clearly causing site failures, and detecting cryptic post-metamorphic frogs across large wetland habitats remained a persistent monitoring challenge. The project rates itself partially successful overall, crediting repeated multi-year releases for the successes achieved while attributing failures at some sites to disease, introduced fish, and frogs' possible inability to locate suitable habitat.