Home Range and Movements of Rhabdophis tigrinus in a Mountain Habitat of Kyoto, Japan

Abstract

We conducted a radio-tracking study on Rhabdophis tigrinus to assess its spatial ecology in the Ashiu Forest Research Station, Kyoto, Japan from 2009 to 2010. The study site is located in a temperate mountain area and includes forests, grasslands, a river, open riverbanks, and small brooks. We estimated the width and area of home ranges for 11 and 10 individuals, respectively. Home range size showed a large individual variation, with home range width ranging from 97 to 997 m and area ranging from 1.3 to 11.0 ha. We did not find obvious sexual differences or effects of body size on home range size. Tracked snakes tended to aggregate in riverside areas in spring, although females were sometimes found away from the river. Compared to spring, snakes in summer and fall were relatively dispersed and more likely to be located in brookside areas or places apart from water bodies. Eight individuals moved from riverside areas to brookside areas in summer. We located hibernation sites of nine individuals. Before hibernation, four individuals moved to a mountain ridge or a steep rocky slope where snakes were never found in warmer seasons, whereas the other five individuals hibernated within their warm-season home range. Neither sex nor body size seemed to be related to the occurrence of migratory movements in summer and before hibernation. Previous studies based on visual surveys have suggested bimodal seasonal activity of R. tigrinus, with peaks in spring and fall. However, activity of the tracked snakes in our study did not decrease in summer compared to that in spring, suggesting underestimation of summer activity in the visual survey method. Our results suggest that R. tigrinus migrates to use different habitats among seasons, although there is individual variation in migratory behavior.