No evidence of non-assisted northern leopard frog (Lithobates pipiens) recovery in southern Alberta, Canada

Background/Question/Methods

Dramatic decreases in northern leopard frog (NLF) abundance and distribution were first reported in western Canada and the USA in the 1970s and 80s. As a result of this decline, the western boreal/prairie populations of NLF are designated as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and Threatened under the Alberta Wildlife Act. Recovery efforts have primarily focused on reintroducing NLFs to historical portions of their former range. Recovery efforts are hampered by the fact that little is known about the population dynamics and current distribution of NLF in this region. To address this knowledge gap we conducted repeat visual surveys over three summers at 68 sites spanning 90,000 km² of southern Alberta. Sites were selected based on historical observations of NLF and those predicted to be suitable habitat. We used occupancy modeling to explore the population dynamics of northern leopard frogs (NLF) in southern Alberta.

Results/Conclusions

Using AIC we compared models that allowed occupancy, and extinction/ colonization to vary with equilibrium models. Only the top model had a DAIC<2 indicating substantial support and comprised 57% of the AIC weight. This model was an equilibrium model with constant occupancy and constant rate of colonization/extinction suggesting that NLF occupancy over the course of our study was stable. While we are cautiously optimistic that the population distribution of NLFs is not continuing to decline, there is no evidence that they are recovering in their former range.