Factors influencing the timing of spring migration in common toads (Bufo bufo)

We analysed 12 years of data on the spring migration of the common toad Bufo bufo L. to breeding ponds across 25 locations in Derbyshire, UK, to determine factors influencing the number of toads active per night. We also tested whether the timing of spring migration is predicted by annual variation in temperature or precipitation. More toads migrate in warmer temperatures and as the moon waxes, whereas precipitation did not have a significant effect on toad activity. Across years, spring migration begins earlier in warmer years, but the main migration of toads was not predicted by air temperatures before the onset of the breeding season. Contrary to the majority of studies of amphibian breeding phenology, there has been a temporal shift towards later timing of breeding over the past 12 years. Overall, comparison of our results with that of previous studies suggests that it can be difficult to generalize about the factors that influence breeding phenology, even within species. However, as more studies accumulate, it should be possible to address whether variation in breeding phenology is consistently linked to geographic variation in abiotic conditions or species biology, which will help to evaluate its consequences under climate change.