Effects of Climate Change on the Breeding Phenology of Newts

Phenological advancements have been documented in a variety of taxa in response to climate change. Amphibians have mostly been studied in the northern hemisphere with the majority of responses suggesting an advancement in breeding dates in line with increasingly warmer spring temperatures. This study looked at various aspects of the breeding phenology of palmate, smooth and great crested newts at two neighbouring metapopulations in Canterbury, Kent, UK over a period of 20 years. Median date (seasonality), duration of aquatic period and individual body condition were analysed to identify any changes over time and then again to identify any relationships with climatic factors. The responses varied between pond and species: great crested newts showed a delay in median capture date and a lengthening in duration of aquatic period at two out of five ponds, plus an increase in body condition; palmate newts showed a delay in median capture and lengthening of duration at one pond; and smooth newts showed a lengthening in duration at two of the five ponds. There does appear to be a relationship with climate, but as the changes in phenology were not observed at all ponds within the same local climatic region, it suggests that the effects of climate change may be indirect, and local conditions may compensate or override any potential climate-related effects. This study is the first to document delayed breeding activity in great crested and palmate newts, and the first for urodeles in Europe. These contrasting results show that amphibians are responding to environmental changes at a population level and therefore climate change mitigation measures may need to be population-specific.