Abstract
Plestiodon kishinouyei is the largest skink in Japan and is endemic to Miyako and Yaeyama Islands, located in the southern part of the Ryukyu Archipelago, Japan. It is considered to be heliothermic and thus exclusively diurnal. However, I observed this species to be active on Iriomote-jima Island several times at night. Nocturnal activity was recorded mostly on rainy nights and exclusively in fall, whereas most daytime activity was observed on days without rain and in the summer. These field observations suggest that P. kishinouyei is occasionally active at night. To better understand its thermal ecology, further studies of the nocturnal habits of P. kishinouyei should be performed.
