Vol. 39 No. 2, 2000

No Divergence of Habitat Selection between Male and Female Arboreal Snakes, Trimeresurus s. stejnegeri

Ming-Chung Tu*, Shiuang Wang and Yu-Chun Lin

Department of Biology, National Taiwan Normal University, Taipei, Taiwan 116

Ming-Chung Tu, Shiuang Wang and Yu-Chun Lin (2000) Sexual dimorphism in body size is a common phenomenon among animals, and possibly 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 heavier female arboreal snakes, Trimeresurus s. stejnegeri, may use thicker or lower branches than males. We visited 2 field-sampling sites and 1 outdoor enclosure regularly to check the micro-habitats that were used by adult T. s. stejnegeri. Totally 872 observations of 202 mature snakes were recorded from August 1996 to October 1997. The results contradicted our expectation. No difference in habitat selection between females and males was found in the measured parameters. Limited differences in size between the sexes and the physical structure of plants may account for this negative result. All snakes perched on thinner twigs more frequently than thicker branches. Twigs of diameter larger than 2 cm were rarely used by snakes. We found a significant vertical movement between day and night by the individuals in all 3 locations. 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.

Key words: Habitat, Sex, Arboreal, Snake, Pitviper.

*Correspondence: Tel: 886-2-29336875 ext. 321. Fax: 886-2-29312904. E-mail: biofv026@scc.ntnu.edu.tw