Behavioral responses to a change in stimulus: transport vs. attack behavior in a carnivorous land snail, Haplotrema concavum

Haplotrema concavum, a carnivorous land snail, responds differently to the same prey when hunting versus when transporting food. The ability of these animals to distinguish between fresh, unmanipulated or uneaten prey and man ipulated or partially eaten prey was tested by switching prey items while t he predator was in the process of transporting the prey. Predators responde d to a switch from a manipulated egg of Anguispira alternata to an unmanipu lated egg by suspending transport behavior while the new egg was manipulate d. Seven of ten predators responded to a switch from an egg of A. alternata to a conspecific (H. concavum) egg by stopping transport and abandoning th e less-preferred food. Predators responded to a switch from partially eaten hatchlings of A. alternata to fresh but injured hatchlings by stopping tra nsport after the retrieval stage to eat the new hatchling, after which tran sport was resumed. Predators which were not engaged in transport behavior a ttacked rather than retrieved fresh, injured hatchling prey. These results suggest that by manipulating its prey, the predator alters the sensory stim ulus of the prey by marking the prey with predator mucus which, in turn, el icits the transport behavior by the predatory snail.