Meeting Abstract

110.5  Saturday, Jan. 7  Proximate And Ultimate Perspectives On One-Trial Learning In Rattlesnakes KROCHMAL, A.R.*; LADUC, T.J.; PLACE, A.J.; Washington College; The University of Texas at Austin; Northwestern Oklahoma State University akrochmal2@washcoll.edu

Little empirical work has focused on decision-making and learning in snakes. The few studies that have been conducted generally lack biological relevance and a phylogenetic framework, curtailing their scope substantially. We investigated the ability of 13 pitviper species – 7 rattlesnake and 6 non-rattlesnake pitvipers – to escape from a thermally stressor. Though all species were able to escape the thermal stress equally well, rattlesnakes in the study learned to escape in one trial (i.e., escape in 11 subsequent trials was faster than trial 1), whereas non-rattlesnake pitvipers never decreased their escape time over the 12 trials. Herein, we offer both proximate and ultimate mechanisms explaining one-trail learning in rattlesnakes. We used signal detection theory (SDT) to model the possible proximate neural mechanisms underlying the observed differences in learning between rattlesnakes and non-rattlesnake pitvipers. Our SDT model suggests profound differences in the neural processing abilities between the brains of rattlesnake and non-rattlesnake pitvipers, and we predict marked anatomical differences in the medial and lateral cortices of the cerebra of these lineages. At the ultimate level, we propose that the observed learning patterns could have arisen to aid in navigating an extreme and variable thermal environment, an idea supported by behavioral studies and the biophysical profile of the region in which rattlesnakes likely arose. Alternatively, the high predation pressure presumed to have driven the origin of the rattle could have also selected for one-trial learning relative to a suite of behaviors. Our results, and our hypotheses explaining them, underscore the need for future empirical studies of both the function, and mechanisms of learning in rattlesnakes.