Early measures against alien Eurasian red squirrels in the Sayama Hills

Abstract

The invasive alien species, the Eurasian red squirrel (Sciurus vulgaris), was reported to establish in the Sayama Hills, Kanto Plains, in 2000. The Mammalian Society of Japan submitted the request form in November 2013 to the Ministry of Environment to start countermeasures immediately. In April 2014, the Ministry of the Environment started a survey to clarify the distribution of alien squirrels in the Sayama Hills, and at the same time, started to capture the squirrels. We found squirrels at 17 points by sighting, food remains, and monitoring cameras. A trapping survey at 17 points also captured 32 individuals of S. vulgaris and one individual of S. lis over three years. After that, sighting information ceased, and monitoring camera did not detect the squirrel anymore. We suggest that the early countermeasures were successful, but we need further investigations to know whether alien squirrels remain in Sayama Hills, or if they dispersed to the surrounding forests.