Pheromones in snakes

FIGURE 7.3 Sex pheromones in garter snakes, (fl) Methyl esters in the attractiveness pheromone of females, (h) Squalene, which forms part of the male sex recognition system. 

Although the database from experimental studies of pheromone trailing behavior in snakes is small, it is apparent from this review that such work is quite valuable in evaluating the role of olfaction in snake sociobiology. Trailing activity can be used as an easily quantified visual bioassay of chemosensory input relating to the various social responses of snakes. In addition, aspects of this activity may be useful in other disciplines of herpetology (i.e., evolution and taxonomy). 

Garstka, W., and Crews, D., 1981, Female sex pheromone in the skin and circulation of a garter snake. Science, 214 681. 

Crews 1977). In addition, a pheromone associated with the copulatory plug in the plains garter snake (Thamnophis radix) renders captive males sexually refractory for periods of 24-72 h after exposure (Ross Crews 1978). Thus, there appear to be pheromones in the copulatory plug that not only render mated females temporarily unattractive, but also cause sexually active males to become sexually quiescent, ceasing courtship behavior after exposure to this pheromone. Similar studies in the Swedish viper (Vipera berus) did not yield any behaviors similar to those exhibited by garter snakes (Nilson Andren 1982). 

Costanzo, J. 1989. Conspecific scent trailing by garter snakes (Thamnophis sirtalis) during autumn further evidence for use of pheromones in den location. J. Chem. Ecol. 15 2531-2538. 

Ford, N.B. D. Holland. 1990. The role of pheromones in the spacing behaviour of snakes. In Chemical Signals in Vertebrates, 5, eds. D.W. Macdonald, D. Miiller-Schwarze S.E. Natynczuk, pp. 465-472, Oxford University Press, Oxford. 

Graves B.M., Halpem M. and Friesen J.L. (1991). Snake aggregation pheromones source and chemosensory mediation in Western Ribbon snakes (Thamnophis proximus). J Comp Psychol 105, 140-144. 

To examine variation in the quality of methyl ketones expressed by females and newly-emerged males, we determined the number of unique methyl ketones expressed by individual snakes and compared the relative concentrations of individual methyl ketones comprising the overall pheromone profiles for the two groups. The methyl ketones present in the pheromone extracts were identified by gas chromatography / mass spectrometry (Hewlett Packard 5890 Series II gas chromatograph coupled with a Hewlett Packard 5971 Series mass selective detector— see LeMaster and Mason 2003 for full description of the GC/MS platform and methods). 

Ford, N.B. (1981) Seasonality of pheromone trailing behavior in two species of garter snake, Thamnophis (Colubridae). Southwest. Nat. 26, 385-388. 

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. 

LeMaster, M.P and Mason, R.T. (2002) Variation in a female sexual attractiveness pheromone controls male mate choice in garter snakes. J. Chem. Ecol. 28, 1269-1285. 

Male garter snakes do not pursue already mated females. These females carry a gelatinous mating plug in their cloaca for about 2 days. Copulatory fluids around her cloaca contain a copulatory pheromone that inhihits males advances. Males detect this copulatory pheromone on a female s trail hy tongue flicking from a distance (O Donnell etat. 2004). 

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... 

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