Ontogenetic and interspecific variation in timing of movement and responses to climatic factors during migrations by pond-breeding amphibians

Pond-breeding amphibians from temperate regions undertake overland migrations to reproduce in aquatic habitats. In turn, their offspring metamorphose and emigrate to upland, terrestrial habitats. We examined the diel patterns and daily variability of migrations of adult and juvenile amphibians in response to climatic cues. Of the eight species (Ainbystoma talpoideum (Holbrook, 1838), Ambystoma tigrinum (Green, 1825), Bufo terrestris (Bormaterre, 1789), Hyla gratiosa LeConte, 1856, Pseudacris crucifer (Wied-Neuwid, 1838), Pseudacris ornata (Holbrook, 1836), Rana sphenocephala Cope, 1886, and Scaphiopus holbrookii (Harlan, 1935)) that we observed, all migrated almost exclusively at night except for the recently metamorphosed B. terrestris, which frequently migrated diurnally (> 50% of captures). Additionally, we correlated daily captures of adult and juvenile A. talpoideum, A. tigrinum, B. terrestris, and R. sphenocephala to maximum and minimum daily temperatures, number of previous days without rain, total rainfall during the previous 24 h, and interactions of these variables. Rain was often the most important predictor of amphibian movements. However, species differed in their response to climatic factors, with some species and age classes being more dependent on rain for migrations than others. Rapid changes in regional weather patterns may affect species' migrations differently, possibly altering arrival times of reproductive adults or affecting the likelihood of successful migrations.