Early onset of breeding season in the green toad Bufotes viridis in Western Poland

Amphibians are highly sensitive to environmental changes such as climate warming. Here, we report unusually early oviposition in two spatially isolated urban subpopulations of the green toad Bufotes viridis Laurenti, 1768, in Poznan, Western Poland. To our knowledge, we report the earliest breeding date for Central and Eastern Europe, for areas of similar latitude. We ascribe the early onset of B. viridis reproduction to an exceptionally warm spring in Western Poland in 2017. B. viridis shows flexibility in the timing of reproductive activity, however, shifts in breeding phenology may have both beneficial and detrimental population consequences.