Intraspecific Geographical Variation in Chemical Food Cue Preferences of Newborn Garter Snakes (Thamnophis Sir Talis)

Abstract

AbstractFour litters of garter snakes (Thamnophis sirtalis) born to females captured in three different geographic areas were tested on their responses to an identical series of water extracts prepared from the surface substances of 15 small animals in addition to a distilled water control. Two of the litters came from northern Illinois; the others were from western Iowa and northern Wisconsin. From each litter 21 previously unfed snakes were tested on the fourth and fifth days after birth. The stimuli were presented on cotton swabs, and the number of tongue flicks, as well as attacks and their latencies, were recorded. The four litters shared a basic similarity in the kinds of extracts attacked. However, the relative effectiveness of the extracts varied considerably with the two Illinois litters most alike in their "ranking" of the various stimuli. Thus, geographical differences in responses to chemical cues within a species were shown. A good example of this was seen in the responses to the fish and earthworm extracts. While the two Illinois litters attacked both frequently, the Wisconsin litter attacked the fish much more than the worms and vice-versa for the Iowa litter. Correlations between the various response measures are presented also.