Ontogeny of predatory behavior in the aquatic specialist snake, Nerodia rhombifer, during the first year of life

Abstract

We conducted two laboratory experiments in order to examine the predatory behavior of neonatal water snakes, Nerodia rhombifer. The first experiment determined habitat use and predatory behavior in three litters of preyand habitat-naive neonates in small, naturalistic enclosures. The second experiment tested one litter of snakes at three ages from birth to one year in the same enclosures in order to determine ontogenetic changes in habitat use and predatory behavior. The neonates were highly aquatic, foraging only while in water. While negatively buoyant, they focused their activity at the surface of the water. Neonatal snakes were very successful at attacking live fish, capturing most by the head or repositioning them rapidly to a head-first position. The open-mouthed (OM) foraging behavior typical of adults was only rudimentarily developed. Ontogenetic changes in habitat use included a shift to less dense cover and increased use of open water. Ontogenetic changes in behavior included increased underwater activity and decreased surface activity, a higher rate of attacking, and shorter handling times, although snakes captured fewer fish by the head. OM foraging behavior developed, but was still abbreviated as compared to adults at the end of the year. Field studies corroborate the results of these studies.