The Herpetological Journal

pp.110-114 

Authors: Gordon H. Rodda

Abstract: Boiga irregularis is a nocturnal, primarily arboreal, rear-fanged colubrid that is believed to have eliminated most of the native forest vertebrates on the island of Guam. On Guam it usually eats birds, rats, and lizards, including both day and night active species. To determine where the snakes forage, I tabulated 398 sightings of foraging snakes, recording their perch height, perch diameter, and perch plant species. These measures were compared to the places where searchers look for snakes, as well as the heights and perches where likely prey items are seen. Snakes were seen less often than would be expected based on search effort at heights from 2-5 m above ground. The modal height for foraging snakes was less than 0.5 m and they exhibited no preference for perch diameter. To determine how the snake locates its prey I watched 26 snakes for a total of 1 9.45 hours using a night-vision device. Both active search and ambush foraging modes were evident, with many snakes using both tactics within an evening. The postures adopted by immobile snakes suggest that they could detect the odor tracks of geckos. I also observed one medium-sized snake consume a sleeping adult columbid bird, which it found by active search.