Effects of temperature and precipitation changes on shifts in breeding phenology of an endangered toad

Abstract

In the last century, a plethora of species have shown rapid phenological changes in response to climate change. Among animals, amphibians exhibit some of the greatest responses since their activity strongly depends on temperature and rainfall regimes. These shifts in phenology can have negative consequences for amphibian fitness. Thus, understanding phenological changes in amphibians is pivotal to design conservation actions to mitigate climate change effects. We used data on Common Spadefoot Toad (Pelobates fuscus) reproductive migration to wetlands over a period of 8 years in Italy to (i) identify the factors related to breeding migrations, (ii) assess potential phenological shifts in the breeding period, and (iii) determine which climatic factors are related to the observed phenological shifts. Our results showed that toads migrate to spawning sites preferably in early spring, on rainy days with temperatures of 9–14 °C, and with high humidity. Furthermore, despite an increase in average temperature across the study period, we observed a delay in the start of breeding migrations of 12.4 days over 8 years. This counterintuitive pattern was the result of a succession of hot and dry years that occurred in the study area, highlighting that for ephemeral pond breeders, precipitation could have a larger impact than temperature on phenology. Our results belie the strong presumption that climate change will shift amphibian phenology toward an earlier breeding migration and underline the importance of closely investigating the environmental factors related to species phenology.

Climatic drivers of chytrid prevalence in the critically endangered Admirable Redbelly Toad

“…The waterborne fungal pathogen Batrachochytrium dendrobatidis (hereafter Bd) causes the disease chytridiomycosis in amphibians and has been implicated in population declines and extinctions globally (Scheele et al 2019). Moreover, alterations in temperature and rainfall patterns are known to impact the onset of breeding phenology in amphibians (Dalpasso et al 2023). Amphibian Bd infection could be also in uenced by seasonal temperature and rainfall patterns (Ruggeri et al 2018;Turner et al 2021).…”