Feeding preferences in 2 disjunct populations of tiger snakes, Notechis scutatus (Elapidae)

Variations at both the genetic and phenotypic levels play an important role in responses to food and food-related stimuli. Knowledge of such variations is crucial to understanding how populations adapt to changing environments. We investigated the dietary preferences of 2 tiger snake populations and compared the responses of diet-naive animals (laboratory-born neonates), diet-controlled animals (laboratory-reared juveniles), and natural diet-experienced animals (wild-caught adults) to visual and chemical cues from 6 prey types (mouse, skink, silver gull, chicken, shearwater, and frog). The mainland population inhabits a swamp, feeds mostly on frogs, and suffers heavy predation. The second population inhabits a small nearby offshore island with no standing water (no frogs); feeds mostly on skinks, mice, and, as adults, silver gull chicks; and suffers no known predation. Although different prey are eaten in the 2 populations, adult wild-caught snakes from both populations showed a significant preference for 3 types of prey (frog, mouse, and chick), irrespective of their natural diet. Neonates responded to all prey cues more than they did to control stimuli in both populations. However, the island neonates showed significantly higher interest in silver gull chick stimuli (the main prey of the island adult snakes) than did their mainland conspecifics. Laboratory-bred juveniles displayed behavioral plasticity by significantly increasing their response to mice after being fed baby mice for 7 months. We conclude that genetic-based differences in food-related cues are important in tiger snakes but that they are also capable of behavioral plasticity. Island adult and neonate snakes exhibited responses to prey types no longer consumed naturally (frog), suggesting that behavioral characters may have been retained for long periods under relaxed selection. Island neonates showed a strong interest in a novel prey item (silver gull). This result complements previous work describing how island snakes have developed the ability to swallow larger prey than usual, as well as seemingly developing a taste for them.