Animals ¢.

In order to achieve copulation, a male snake must align his body in the same direction as his mate. This may not be a trivial problem in an elongate limbless animal, especially when the male is much smaller than the female (and hence, his head is far from hers) and when she is simultaneously being courted by many other males (so that much of her body is not visible). This is exactly the situation experienced by red-sided gartersnakes (Thamnophis sirtalis parietalis) at communal dens in Manitoba. To clarify this question, we modi ed cues available to males by manipulating various attributes of females (direction of movement, presence of head and tail, concentration of sex pheromones, etc.). Male alignment during courtship does not depend on the visual stimulus provided by the female ¢ s head or tail. Instead, male alignment is in uenced by the female ¢ s direction of movement, and by pheromonal stimuli from her skin. We suggest that courting male snakes obtain directiona