Changing Temperatures Are Affecting Ontario’s Amphibians

December 5, 2012

Wood Frog by Lynda Ruegg

Article by: Shannon Ritchie

In the journal of Herpetological Conservation and Biology, an interesting study was published entitled “Community-Level Reponses to Climate Change: Shifts in Anuran Calling Penology” (Walpole et al., 2012). This study links the warming effect of climate change to the change in reproductive timing of amphibians in the Lake Simcoe watershed. Using 14 years of spring to summer temperatures and peak calling data, it showed that early spring breeders such as the Wood Frog (Lithobates sylvaticus), Spring Peeper (Pseudacris crucifer), and Northern Leopard Frog (L. pipiens) called earlier in the season over time, as temperatures increased. However, late breeders such as the Green Frog (L. clamitans) did not adapt to call earlier then their expected peak calling time.

Leopard Frogs Mating by Jennifer Howard

The study indicates that there is a relationship between temperature and initiation of breeding for some amphibian species, however not all amphibians follow this trend. This study also found that the effect of climate change can influence shifts in amphibian communities over a short period of time (<14 years). Species that were most influenced by temperature affecting their peak calling time were the earliest amphibian breeders in Ontario, the Wood Frog and Spring Peeper; both of which are known to begin calling even when winter ice is still present.

Spring Peeper By Lynda Ruegg

The impact of earlier peak calling by climate change is unique to each species’ ecological requirements. By shifting the time of reproduction, food sources and important interactions between species in a community can be disrupted. For example, having a large population of Wood Frogs mature before American Toads may directly influence availability of food. Better utilization of vernal pools, which dry up as summer progresses, can be seen as a benefit of earlier peak calling periods, as vernal pools are important nursery habitats for both frogs and salamanders because these seasonal habitats contain less predators compared to permanent water habitats. Using the climatology models, the Lake Simcoe watershed is expected to have advanced wetland hydro-periods and an increase in mean spring temperatures of 4^oC by 2100. This could result in both Spring Peepers and Wood frogs calling and reproducing up to 11 days earlier.

Although we can speculate on the impact climate change will have on our amphibian friends, there is no way to know for certain how they will be affected.

The FrogWatch programme is a great way for individuals to track changes in their local frog populations. Data gained from FrogWatchers can be use to model changes in their population over time and locate hotspots for wetland conservation. To learn more about the FrogWatch programme visit our webpage at:

http://torontozoo.ca/AdoptAPond/FrogWatchOntario.asp