Behaviour to avoid saltwater sites during spawning in Buergeria japonica (Hallowell, 1861)

Abstract

The use of spawning sites by female amphibians can strongly influence the rate of egg survival. Coastal areas are risky environments for amphibian breeding because the rate of egg survival falls drastically with increased water salinity. Buergeria japonica is an anuran species that breeds in coastal environments but avoids spawning in sites with increased salinity. The aim of this study is to understand the behavioural sequence of how this frog avoids saltwater sites. To address this question, I recorded spawning behaviour in a laboratory experiment. Although amplectant pairs randomly visited and entered fresh and saltwater sites, they rapidly left saltwater sites after entering the water. The amount of time spent in saltwater sites prior to exiting the water declined with increasing water salinity. The selection of a spawning site was determined by gravid females only because each male was clasping onto the back of the female and did not contribute to the locomotion of amplectant pairs. This result suggests that female B. japonica are able to quickly determine the salinity level of potential breeding sites. Together, all adaptive responses allow this species to persist in a coastal environment, in which salinity of breeding sites varies greatly.