No divergence of habitat selection between male and female arboreal snakes, Trimeresurus s. stejnegeri

Sexual dimorphism in body size is a common phenomenon among animals, and po ssibly allows the sexes to exploit different habitats. In snakes, low body mass is valuable for arboreal life because it enables the exploitation of a wider range of habitats. Therefore, we would predict that larger and heavi er female arboreal snakes, Trimeresurus s. stejnegeri, may use thicker or l ower branches than males. We visited 2 field-sampling sites and 1 outdoor e nclosure regularly to check the micro-habitats that were used by adult T:s. stejnegeri. Totally 872 observations of 202 mature snakes were recorded fr om August 1996 to October 1997. The results contradicted our expectation. N o difference in habitat selection between females and males was found in th e measured parameters. Limited differences in size between the sexes and th e physical structure of plants may account for this negative result. All sn akes perched on thinner twigs more frequently than thicker branches. Twigs of diameter larger than 2 cm were rarely used by snakes. We found a signifi cant vertical movement between day and night by the individuals in all 3 lo cations. Snakes in the outdoor enclosure showed a greater tendency to perch on higher branches than did those in the field. In the field, more than 93 % of snakes were found at a height of less than 4 m. However, less than 64% of snakes were found within 4 m of the ground in the outdoor enclosure.