The interaction of food motivation and experience in the ontogeny of chemoreception in crayfish snakes

Precocial offspring are often required to recognize and acquire food without assistance. In addition, they must be able to respond to changes in prey availability. We studied two species of crayfish snake (Regina septemvittata and R. grahamii) to compare the effect of the availability of their preferred prey, freshly moulted crayfish, on the ontogeny of chemosensory response towards different prey types (fish, odonate larvae, intermoult crayfish and freshly moulted crayfish). A split litter design was used; within each species, litters were divided into three groups for testing at different ages (7, 14 and 21 days) and then within each age group, individuals were assigned to treatment groups that were fed or not fed prior to testing. The results of this study confirm that R. grahamii and R. septemvittata are born with chemosensory prey preferences that reflect their specialized diets. However, the ontogeny of these preferences is modified by food availability and available energy levels. Significantly, the pattern of development that emerged in the groups deprived of food differed between species. Regina septemvittata neonates had limited yolk and fat reserves and rapidly increased their interest in alternative prey types, whereas R. grahamii neonates, with significantly more reserves, did not increase their responses to alternative prey. These differences may reflect alternative survival strategies of newborn snakes that have different amounts of energy reserves at birth.