Larval performance and oviposition habitat selection of the tree frog, Hyla savignyi, in response to conspecific larval density

Amphibians breeding in temporary pools may experience strong intraspecific density-dependent effects in the form of larval competition and oviposition site selection. These potential effects are untested for the tree frog, Hyla savignyi, an anuran species of conservation concern in Israel. We conducted an outdoor mesocosm experiment to examine how intraspecific larval density may affect larval performance and oviposition habitat selection in H. savignyi. We added ecologically relevant densities of 0, 10, or 40 early-stage tadpoles into mesocosms (plastic tubs) containing 20 L of water. Each density was replicated with four tubs. Time to and size at metamorphosis were not significantly affected by initial H. savignyi density. However, strong intraspecific competitive effects were observed in the form of reduced size at metamorphosis at the high density. We also found that gravid H. savignyi females reduce future intraspecific competition for their progeny by choosing to oviposit in mesocosms with no, or low, densities of H. savignyi tadpoles. Thus, intraspecific competition in this anuran species appears to be an important factor at ecologically relevant densities; larval competition increases with increasing densities and may be avoided by gravid females assessing breeding habitat quality in the form of conspecific tadpole density or mass.