Shifts in breeding phenology linked to climate change have been increasingly documented across animal taxa. Earlier spring activity and delayed autumn inactivity can prolong breeding seasons, but they may also expose early life stages to unsuitable or unpredictable environmental conditions.

In Italy, most amphibians reproduce between late winter and early spring, allowing tadpoles to develop in relatively stable water bodies sustained by spring rainfall. Overwintering tadpoles—typically the result of reproduction in late autumn or early winter—are well known for Bufo boulengeri populations in Southern Italy, where the strategy is viewed as an adaptation to arid climates. However, such cases are virtually absent among amphibian species in the northern regions of the country.

A forthcoming article in Acta Herpetologica provides the first documented evidence of overwintering tadpoles in the endemic Italian agile frog (Rana latastei), a species restricted to the lowlands of Northern Italy. The observation was made in January–February 2025 in a small, artificial, permanent pond in the province of Como (Lombardia). Researchers recorded several large tadpoles (Gosner stage 37 or higher) and a newly metamorphosed froglet, co-occurring with numerous newly hatched tadpoles. The size and developmental stage of the larger individuals strongly suggest they originated from breeding events in the previous year, indicating they survived an overwintering period—an unexpected phenomenon for a species that typically breeds early in the season.

While a late-autumn or early-winter 2024 breeding event cannot be ruled out, the possibility remains that the tadpoles hatched in spring 2024 and experienced delayed development due to adverse environmental conditions. Regardless of timing, the observation represents the first verified case of overwintering R. latastei tadpoles.

This finding underscores the importance of expanding monitoring efforts into the autumn months to determine how frequently this phenomenon occurs, as well as to clarify its drivers and ecological implications within the context of shifting breeding phenology.

Read the full paper to learn more.

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