Effects of Early Feeding Experience on Chemical Preference of the Northern Water Snake, Natrix s. sipedon (Reptilia, Serpentes, Colubridae)

Motion picture analyses of tongue flicking behavior by 15 neonate northern watersnakes (Natrix s. sipedon) to chemical extracts were used to investigate possible evidence for: (1) increased tongue flicking to air-borne chemicals; (2) modificaton of chemical preference by early feeding experience; (3) a relationship between the number of tongue flicks per extract and the mean flick duration. A novel technique for presenting only air-borne chemical extracts without any visual cue indicated more tongue flicking by s. sipedon to air-borne odors of frog extract than to a distilled water control. Early feeding experience had no effect on subsequent chemical preference. Natrix s. sipedon demonstrated a preference for extracts from a sympatric species of frog (Rana sylvatica) but not for extracts from a nonsympatric species of fish (Gambusia affinis), regardless of being fed exclusively on either this species of frog or fish or on earthworm (Lumbricus terrestris). This finding supports the hypothesis that newborn snakes show innate preference for sympatric species of normally eaten prey, and further suggests that this preference predominates over the effect of early feeding. A significant correlation between increasing number of tongue flicks and increasing mean flick duration was found only for presentations of distilled water. A relationship between increased number of tongue flicks and longer flick duration for preferred odors may be masked, since these