Laboratory observations of aggregative behavior of garter snakes, Thamnophis sirtalis: Roles of the visual, olfactory, and vomeronasal senses.

Two experiments determined (a) whether male garter snakes require a functional vomeronasal or olfactory system to return to previously preferred shelter locations and (b) the sensory modalities used to aggregate in the absence of previously deposited chemical cues. In Exp I, 22 male garter snakes with vomeronasal nerve lesions did not return to previously preferred shelter locations when tested individually. However, when tested with a group that included 9 control Ss, they returned to previously preferred shelters. The shelter-selection behavior of Ss with olfactory nerve lesions improved postoperatively, whereas the behavior of Ss with sham lesions was unchanged. In Exp II, 32 Ss were tested for aggregation in aquaria in which the substrate and other contents were cleaned between trials. After blindfolding or olfactory nerve cuts, Ss aggregated at normal levels. When Ss' vomeronasal ducts were sutured closed, aggregation scores were significantly depressed, although 2 of the 3 groups with vomeronasal duct sutures did aggregate just above change levels. Results from both studies indicate that use of chemical signals by garter snakes in shelter selection and aggregation is mediated by the vomeronasal system and that neither the olfactory nor the visual system is critical for these behaviors. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)