Study of the Habitats, Burrowing Behavior, Physiological Adaptation and Life Cycle of Spadefoot Toad (Pelobates syriacus, Boettger, 1869) at the Southern Limit of Its Distribution in Israel

The present study describes the habitats, life cycle, larval growth, burrowing behavior and terrestrial adaptation of spadefoot toads (Pelobates syriacus) in Israel based on observations and data collected over more than 30 years in northern Israel. The distribution area in Israel is from the north in the Upper Galilee and Golan Heights (annual rainfall range of 500–1000 mm) to the southern coastal plain (annual rainfall of about 250 mm). Among the 51 different breeding places of amphibians, only ponds where water is available for a few months of the year were used by spadefoot toads and metamorphosed populations were found around these ponds. The larvae underwent metamorphosis during the summer and autumn in northern Israel, and during the spring in central and southern Israel. The percentage of toads burrowing was negatively correlated to soil moisture levels, i.e., greater burrowing behavior occurring under dry conditions. Plasma concentrations of electrolytes and urea increased during burrowing. The burrowing behavior helps the spadefoot toads survive in this area at the southern border of its distribution. Spadefoot toads are highly specialized and have a narrow ecological niche that selects for lower levels of diversity.