Comparison of Prey-Handling Behavior Among Different Prey Animals in a Generalist Snake, Hebius vibakari vibakari
Prey type has a great impact on evolution of snakes, and ecological, behavioral, and morphological information related to feeding traits is essential for understanding diversity of snakes. In this study, we investigated prey-handling behavior of Japanese Keelbacks (Hebius vibakari vibakari) on different prey animals (earthworms, fish, tadpoles, and frogs). When snakes manipulated prey, all prey animals were simply seized by the jaws and swallowed alive. Earthworms and tadpoles were occasionally swallowed folded, whereas fish and frogs were always swallowed unfolded. In several cases when snakes swallowed frogs from their posterior side, they aligned hind legs of frogs before ingestion. When striking fish, snakes aimed at heads of prey from above water. Prey animals frequently escaped by discharging mucus (earthworms) or struggling vigorously (fish and frogs) after being bitten. We hypothesize that snakes swallowed earthworms folded to avoid being subjected to mucus, aimed at the head of fish because tail movement was more vigorous than that of the head, aligned hind legs of frogs to prevent them from escaping, and simply seized and swallowed tadpoles because these prey lack effective defensive techniques and sufficient power to escape. We suggest that careful observations of instances in which snakes fail to seize prey animals are critical to understanding feeding behaviors of snakes.Abstract
Experimental arena used in this study.
Illustration of HLO and HLA methods in frogs: (A) swallowing posterior-first with hind legs outstretched (HLO), and (B) swallowing posterior-first with hind legs aligned (HLA).
Comparison of manipulation duration among initial bite positions for each prey type. Numerals in parentheses indicate sample size. Horizontal bars: median; boxes: interquartile range; vertical bars: minimum value at q1 (25th percentile) - 1.5 * IQR (interquartile range) and maximum value at q3 (75th percentile) - 1.5 * IQR; n = sample size.
Comparison of swallowing duration among directions of ingestion for each prey type. Numerals in parentheses indicate sample size. Horizontal bars: median; boxes: interquartile range; vertical bars: minimum value at q1 (25th percentile) - 1.5 * IQR (interquartile range) and maximum value at q3 (75th percentile) - 1.5 * IQR; n = sample size.
Relationships between relative prey size (RPS) and handling duration for each prey type.
Relationships between relative body mass (RPM) and handling duration for each prey type.
Contributor Notes
