Ambush Site Selection by a Green Bamboo Pit Viper: Relation to Prey Abundance and Comparison between Juveniles and Adults.

Selecting ambush sites where prey abundance is high is vital for the foraging success of sit-and-wait predators. Ideal ambush sites, however, could vary due to different prey characteristics and intra-specific competition. We examined whether different life stages of a sit-and-wait predator, Trimeresurus stejnegeri, select different ambush sites, based on the observations of ambush sites of juvenile and adult snakes in three water habitats (lentic, lotic, and temporary pools) in Taiwan throughout the year. Snake stomach contents were compared between life stages in each habitat. Correlations between the monthly number of snakes observed and that of each frog species were analyzed for each habitat. Adult snakes mainly used lentic water as ambush sites and rarely used temporary pools, whereas juvenile snakes used all three habitats with a similar frequency. No clear ontogenetic diet shift was found from juveniles to adults. A high percentage of snakes from lentic water habitats had stomachs containing prey, suggesting this habitat is a better site for foraging by both juveniles and adults. Overall, our study highlights that habitat use and behavior of each prey animal and intraspecific competition as well as prey abundance should be taken into consideration when we investigate the factors that affect ambush site selection by predators.