Chemical senses involved in garter snake prey training.

Abstract

Garter snakes were trained to follow earthworm-extract trials in a multiple-choice maze and were subjected to either sham surgery (4) or complete bilateral vomeronasal nerve transection (4). Snakes with sham surgery trailed and ate at preoperative levels, whereas snakes lacking a functional vomeronasal system developed a feeding deficit and trailed at chance levels. In a 2nd experiment, 16 snakes were preoperatively tested for their abilities to follow a battery of trails including a range of trail concentrations and 2 trail manipulations. After baseline testing, the snakes were subjected to sham surgery (2), olfactory nerve transection (7) or vomeronasal nerve transaction (4 partial; 3 complete). Snakes with vomeronasal nerve lesions demonstrated trailing and feeding deficits commensurate with the extent of nerve damage. Snakes with olfactory nerve cuts and sham surgery continued to follow all trails at preoperative levels and maintained high tongue-flick rates when following the stronger extract trails. Four of the snakes (2 with sham lesions, 1 with olfactory nerve lesion and 1 with a partial vomeronasal nerve lesion) were subsequently tested with the vomeronasal ducts sutured closed. These snakes were unable to follow any of the extract trails at better than chance levels, but in contrast to snakes with vomeronasal nerve cuts, most of these snakes continued to attack and ingest earthworm bits. Garter snakes may be heavily dependent on their vomeronasal system for following chemical prey trails.