When choosing between two potential mates, a male may benefit by picking a larger (longer and/or more heavy-bodied) female because she is likely to produce more or larger offspring. Males of many species use visual cues to evaluate the sizes of their mates, but in some situations (at night or in a crowded mating swarm), vision may be useless. Potentially, males may be able to use chemical cues that convey information about female body size. We manipulated cues available to free-ranging male garter snakes (Thamnophis sirtalis parietalis) in large courting aggregations near communal dens in Manitoba, Canada. Males not only directed disproportionate courtship to longer and heavier-bodied females, but also courted most vigorously in response to lipids extracted from the skins of such females. Our data show that with a flick of his tongue, a male garter snake can identify not only a female's body length, but also her body condition.
Bibliographical noteFunding Information:
Acknowledgements We thank D. Roberts, A. Johnson, G. Johnson, and R. Nesbitt for help and encouragement. Financial support was provided by the Australian Research Council, the National Science Foundation, and the Whitehall Foundation (W95–04). Research was conducted under the authority of Oregon State University Institutional Animal Care and Use Committee Protocol No. LAR-1848B. All research was conducted in accord with the U.S. Public Health Service Policy on Humane Care and Use of Laboratory Animals and the National Institutes of Health Guide to the Care and Use of Laboratory Animals, and conforms to all current Canadian laws.
- Garter snake
- Lipids Pheromones
- Thamnophis sirtalis parietalis