Reproductive ecology of Bombina variegata: characterisation of spawning ponds

Abstract

Abstract The use of spawning sites by Bombina variegata was analysed in a dynamic habitat containing a variety of different ponds. Cool or shadowy as well as permanent ponds were not used for spawning at all. Among the ephemeral ponds that were used, egg numbers increased with water temperature, both when compared among ponds and between different areas within ponds. Egg numbers were also higher in ponds of intermediate duration than in those persisting for shorter or longer periods. Ponds of intermediate duration with moderate predator densities and with larvae of competing anuran species (Hyla arborea, Bufo calamita) were used more often than short-lived ponds with no predators and competitors. This pattern of spawn deposition can be interpreted as an attempt to select sites allowing rapid larval development (warm water) and to avoid sites with high numbers of newts and invertebrate predators (permanent ponds). The selection critera seem to be adaptive, because pond duration and desiccation are more important for larval survival than predators and competitors. Yet, optimal reproductive conditions remain highly unpredictable for Bombina variegata, as the characteristics and dynamics of spawning ponds are mainly determined by climatic conditions. Consequently, survival chances of tadpoles can change within a few days or weeks, depending on rainfall and evaporation.