Masters Theses

Lani P. Lyman

Date of Award

8-1990

Degree Type

Thesis

Degree Name

Master of Science

Major

Life Sciences

Major Professor

Gordon M. Burghardt

Committee Members

Arthur Echternacht, John Malone

Abstract

One way in which animals not thought to have complex social interactions can be viewed as nevertheless engaging in truly social behavior is through information transfer. A series of studies were designed to explore and develop this possibility in neonate Butler's garter snakes, Thamnophis butleri (Colubridae). Thirty-eight T. butleri neonates from 2 litters of a Michigan population were measured, then tested prior to feeding for initial chemical prey preference and site choice based on conspecific feces. Animals were then placed into group housing situations of 8 balanced for litter, sex, and initial chemical prey preference, and fed either worms (Lumbricus terrestris) or mosquito fish (Gambusia affinis). Two additional groups consisted of 4 T. butleri housed with 4 T. sirtalis on the same diet. The remaining animals were housed individually. After a maintenance period, snakes were again measured, tested for chemical prey preferences, and tested for site choice based on both conspecific feces and prey surface cues. The animals not housed with T. sirtalis were then observed for aggregation behavior in a large arena with 8 identical shelters, after which all animals were again measured. The main differences in mass and snout-vent length were between the sexes, with males being both heavier and longer than females throughout the study. One litter showed greater increases in mass, the other in length. Snakes also showed a general "slimming" of body shape over the course of the observations. The lack of difference in growth between diets should translate into a negligible difference between health of the subjects. The T. butleri in this experiment showed a preference for earthworm extract over fish extract or a water control prior to feeding experience. The final result after experience with prey was that T. butleri fed worms responded much more strongly to worm than fish cues, while snakes fed fish showed high responses to both prey, slightly favoring fish. In the Initial Feces-Based Choice Test, the animals were shown to have an overall bias in favor of feces carrying worm cues. However, in the Final Feces-Based Choice Test, animals fed fish continued to prefer worm-based feces, while those fed only worms shifted preference toward sites marked with the unfamiliar fish-based feces. There were no preferences demonstrated toward sites marked with prey surface cues. Thamnophis butleri readily aggregated under preferred shelters. Specific pairs of animals could be identified which were more closely associated than others, and these pairs tended to consist of unfamiliar littermates on opposite diets. Animals with very high or low association rates could also be identified. Correlations between various measures demonstrated that measures of growth interacted with aggregation behavior, such that larger snakes had greater distances separating them from their nearest neighbors. There was also some indication that initially smaller snakes showed higher responsiveness to fish cues than larger animals. It is hypothesized that familiarity is the most important factor in aggregative behavior, with dietary experience being secondary. The interactions of dietary experience with the feeding specialization of T butleri, and possibly ancestral chemical preferences are also discussed. Further research into the cues involved in aggregative behavior is suggested.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS