Abstract
Many snakes are uniquely adapted to ingest large prey at infrequent intervals. Digestion of large prey is metabolically and aerobically costly, and large prey boluses can impair snake locomotion, increasing vulnerability to predation. Cessation of foraging and use of refugia with microclimates facilitating digestion are expected to be strategies employed by free‐ranging snakes to cope with the demands of digestion while minimizing risk of predation. However, empirical observations of such submergent behavior from field experiments are limited. The brown treesnake (Serpentes: Colubridae: Boiga irregularis) is a nocturnal, arboreal, colubrid snake that was accidentally introduced to the island of Guam, with ecologically and economically costly consequences. Because tools for brown treesnake damage prevention generally rely on snakes being visible or responding to lures or baits while foraging, cessation of foraging activities after feeding would complicate management. We sought to characterize differences in brown treesnake activity, movement, habitat use, and detectability following feeding of large meals (rodents 33% of the snake's unfed body mass) via radio telemetry, trapping, and visual surveys. Compared to unfed snakes, snakes in the feeding treatment group showed drastic decreases in hourly and nightly activity rates, differences in refuge height and microhabitat type, and a marked decrease in detectability by trapping and visual surveys. Depression of activity lasted approximately 5–7 days, a period that corresponds to previous studies of brown treesnake digestion and cycles of detectability. Our results indicate that management strategies for invasive brown treesnakes need to account for cycles of unavailability and underscore the importance of preventing spread of brown treesnakes to new environments where large prey are abundant and periods of cryptic behavior are likely to be frequent. Characterization of postfeeding behavior changes provides a richer understanding of snake ecology and foraging models for species that consume large prey.
Highlights
Empirical documentation of the postfeeding behaviors of snakes from field experiments is extremely sparse
We propose that the nature and magnitude of such changes are driven by the physiological demands associated with digestion, the need to avoid predation while handicapped by the gastrointestinal prey burden, or both
Our results indicate that the recent feeding of large meals significantly reduces hourly activity levels and detectability of brown treesnakes and is associated with changes in choice of refugium
Summary
Empirical documentation of the postfeeding behaviors of snakes from field experiments is extremely sparse. We know of only two such studies: desert rattlesnakes (Crotalus spp.; Beck, 1996) and a temperate forest colubrid (Elaphe obsoleta; Blouin-Demers & Weatherhead, 2001). Both studies focused on thermoregulation of primarily terrestrial snakes under broad daily temperature fluctuations. We sought to evaluate the behavioral changes exhibited by brown treesnakes following ingestion of large prey items and to interpret our observations in the contexts of behavioral ecology and invasive species management. Others are active foragers, or wide foragers, which move through the environment in search of mobile or nonmobile prey, and have a longer and narrower body form with higher energetic demands and metabolic rates (e.g., Secor & Nagy, 1994). This is a spectrum with most species exhibiting both modes in varying proportions (Perry & Pianka, 1997)
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