2018 Volume 58 Issue 1 Pages 33-40
Pallas’s squirrel Callosciurus erythraeus is a tree squirrel widely distributed in southeast Asia and has been introduced in several parts of Japan. The squirrel is considered a potential avian nest predator based on a few occasional observation records of its egg-predatory behavior. We investigated its significance as an avian nest predator with an artificial nest experiment on Takashima Island, a small islet off the Kyushu mainland, where squirrel density is high. Two each of Japanese quail Coturnix japonica eggs set in artificial nests were lost from 24/25 nests (96%) after three weeks of exposal periods. On all those predated nests, the squirrels were firstly video recorded by infra-red triggered cameras, visiting the nests’ entrances. Jungle crow Corvus macrorhynchos and black rat Rattus rattus, were also recorded on nine nests, but all their visits were far behind the squirrels’ predation events. The estimated average survival time of artificial nests was only 2.7 days, with the average daily survival rate of each nest estimated to be 0.72. Pallas’s squirrel is inferred to be an influential nest predator, due to its characteristic social system allowing the largely overlapping home ranges of individuals and to its very thorough food searching tactics.
