Amphibian Breeding and Climate Change

Abstract: Climate changes may be influencing the breeding patterns of certain organisms. Effects on breeding activities could eventually lead to significant changes in population structure that may be reflected in population declines of species that are especially sensitive, such as some amphibians. Thus, climate changes may have affected the timing of breeding in some European amphibian species. To further test whether amphibian reproductive cycles in temperate countries are responding to climate changes, we conducted an analysis of the breeding phenology of four species of North American anurans for which we have long‐term data sets. Populations of at least two of these species have been declining, and it has been suggested that they and other amphibians may be especially sensitive to climate change. Our results suggest that climate change has not influenced the timing of breeding in amphibians in North America. At one site, in Oregon, a trend (nonsignificant) for western toads ( Bufo boreas ) to breed increasingly early was associated with increasing temperature. At four other sites, however, neither western toads nor Cascades frogs ( Rana cascadae ) showed statistically significant positive trends toward earlier breeding. At three of four of these sites, breeding time was associated with warmer temperatures. The spring peeper ( Pseudacris crucifer ) in Michigan did not show a statistically significant trend toward breeding earlier but did show a significant positive relationship between breeding time and temperature. Fowler's toad ( Bufo fowleri ) in eastern Canada did not show a trend toward breeding earlier, and there was no positive relationship between breeding time and temperature. It did however, show a strong but statistically insignificant trend toward breeding later. The broad pattern emerging from available studies is that some temperate‐zone anuran populations show a trend toward breeding earlier, whereas others do not. It is important to track the breeding patterns of amphibians with long‐term data sets to more fully understand how we can manage threatened populations.