Red-sided garter snakes

A sequence of reptilian studies tracked down the likely signal for mating in Canadian Red-sided Garter snakes. Males respond to products on the female s skin surface, which turn out to be related both to insect cuticular lipids and to those of mammalian skin. These integumentary... 

Fig. 21.1 Proportion (mean SD) of male red-sided garter snakes displaying courtship behavior to small females and newly-emerged males...

Table 21.1 Quantitative and qualitative variation in expression of the methyl ketone profile among small female and newly emerged male red-sided garter snakes... 

LeMaster, M.P. and Mason, R.T. (2001) Evidence for a female sex pheromone mediating male trailing behavior in the red-sided garter snake, Thamnophis sirtalis parietalis. Chemoecology 11, 149-152. 

Male red-sided garter snakes court larger females more than small ones. Even the skin lipid extracts from large females elicit courtship from more males than those from small females. Larger females possess more unsaturated methyl ketones, while small females have more saturated methyl ketones (LeMaster and Mason, 2002). 

Red-sided garter snakes from different regions of Manitoba, Canada show signs of isolation by chemical cues. In choice tests, males from a hiber-naculum (overwintering den) in central Manitoba preferred females from their own population to females from western Manitoba. Males from western Manitoba showed no preference. When confronted with experimental trails, males made the same choices. This demonstrated that a chemical factor is involved. Furthermore, the sexual attractiveness pheromone of females, a series of ty-9-cis-unsaturated methyl ketones, varies between the populations. Specifically, the... 

O Donnell, R. P., Ford, N. B., Shine, R., and Mason, R. T. (2004). Male red-sided garter snakes, Thamnophis sirtalis parietalis, determine female mating status from pheromone trzds. Animal Behaviour 68,677-683. 

The red-sided garter snake pheromone components were isolated by hexane extraction of the skin lipids of sacrificed snakes. Female snakes yielded more total lipid than males (38.4 versus 8.4mg snake-1)80 Initial fractionation on an activity III alumina column gave a fraction (eluted with 98 2, hexanes ethyl ether) that was attractive to courting males. NMR and infrared (IR) spectra of this fraction were suggestive of the presence of methyl ketones, straight chain alkyl lipid subunits, and Z-alkenes. GC—MS analysis, including extensive consideration of the fragmentation of the electron impact MS data, led to the identification of a family of relatively nonvolatile (C29—C37) lipid methyl ketones. Specifically, the individual components of a mixture of saturated and monounsaturated methyl ketones 18—30 were identified. 

Mason, R.T., Jones, T.H., Pales, H.M., Pannell, L.K. Crews, D. 1990. Characterization, synthesis, and behavioral responses to sex attractiveness pheromones of red-sided garter snakes Thamnophis sirtalis pane-talis). J. Chem. EcoL, 16, 2353—2369. 

Friedman, D. W., and Crews, D., 1985a, Role of the anterior hypothala-mus-preoptic area in the regulation of courtship behavior in the male Canadian red-sided garter snake (Thamnophis sirtalis parietalis) Intracranial implantation experiments, Horm. Behav.,... 

Gregory, P. T., 1974, Patterns of spring emergence of the red-sided garter snake (Thamnophis sirtalis parietalis) in the Interlake region of Manitoba, Can. J. Zool., 52 1063. 

---