Northern Leopard Frog Reintroduction Year 3 (2001)


Kris Kendell


The northern leopard frog (Rana pipiens) was once a common and widespread amphibian found throughout central and southern Alberta. During the late 1970s, the leopard frog experienced a dramatic decline in distribution and numbers over much of its historic range in Alberta. As a result, the leopard frog was designated as "Threatened" under Alberta's Wildlife Act in 1996. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) lists the prairie population of the nothern leopard frog as "Special Concern" (COSEWIC 2000). 

In 1998, the Alberta Fish and Wildlife Division began to explire the feasibility of reintroducing leopard frogs into formerly occupied habitats in the upper Red Deer River and North Saskatchewan River drainage basins. Large areas of unsuitable habitat limit the ability of the leopard frog to disperse back into historic parts of its range. As a result, a pilot reintroduction project for the leopard frog was initiated in 1999 at the Raven Brood Trout Station near Caroline, Alberta. The project involved the captive-rearing of leopard frogs from egg stage of development to metamorphosed frog, in two man-made outdoor ponds. 

The primary objective of the project is to re-establish leopard frogs in the headwaters of the Red Deer River and the North Saskatchewan River drainages, consequently allowing natural downstream dispersal along these drainages. Over a three-year period, more than 4500 captive-reared leopard frogs have been released into historic habitat in the upper headwaters of the Red Deer River near Caroline, Alberta. In 2001, 750 young frogs were released at a pilot release site in the upper headwaters of the North Saskatchewan River near Rocky Mountain House, Alberta. All captive-reared and released leopard frogs were marked using a Visible Implant Elastometer (VIE) tagging system that allowed unique marking schemes to be used to assess the success at each release site and monitor the dispersal of released frogs. 

On 19 June 2001, three previously released leopard frogs were found within the study area near Caroline, marking the first occurrence of leopard frogs in that area in nearly 50 years. At least 10 subadult and adult leopard frogs released in previous years were observed or captured within the stufy area in 2001 and calling activity was recorded. Evidence of the overall success of the project at the first release site may be realized in the summer of 2002, when previously released frogs reached sexual maturity, breed and successfully produce young-of-the-year frogs.

During the 2001 field season, 20 potential leopard frog release sites were investigated in the central parkland region of the province and in the upper headwaters of the Red Deer River near Caroline and the North Saskatchewan River near Rocky Mountain House. At each identified site, data were collected on the availability of breeding and summer habitat. In addition, dispersal opportunities into surrounding habitats, including the Red Deer River and North Saskatchewan River drainages, were considered.

Download PDF