SIGNALING OF SEXUAL RECEPTIVITY BY PIGMENTATION PATTERN IN FEMALE STICKLEBACKS

In a marine population of three-spined sticklebacks, Gasterosteus aculeatus, from Long Island, New York, females usually exhibit shiny silver flanks and a pale olive-tan dorsum, which make them cryptic when viewed laterally in the water column. As females become increasingly gravid, they develop a temporary dark mottled or bar-like pattern along their back and upper flanks, which makes them conspicuous when viewed in the water column. Laboratory observations revealed that this pattern is temporally associated with sexual receptivity to courting males. When males were presented with a choice of two dummy females, one with and one without the mottling, the males directed more courtship to the mottled one. This suggests that the mottling pattern may serve to advertise the females' sexual receptivity to territorial males and stimulate the males to court them. © 1991 The Association for the Study of Animal Behaviour.