Seasonal changes in female choosiness

Seasonal changes in female choosiness Åsa A Borg, Elisabet Forsgren, Trond Amundsen Department of Zoology, NTNU, NO-7491 Trondheim, Norway Selectivity in mate choice may vary according to various factors, such as predation risk, variation in mate quality and the operational sex ratio. In this aquarium experiment on the two-spotted goby (Gobiusculus flavescens), we show that female choosiness is not fixed but changes over the season as predicted from changes in operational sex ratios. In this marine fish, males take up nests in which females lay their eggs, thereafter males provide exclusive parental care of the eggs until hatching. Large males are better at defending their nests and might thus be preferred by females. However, the operational sex ratio seems to change over the season, from male biased at the start to female biased at the end. Therefore the opportunity for females to be selective should decline over the season. In simultanous choice tests, performed both early and late in the breeding season, females were allowed to choose between males differing in body length. As predicted, females preferred large males early in the season, but became unselective later on. These results are in accordance with other findings regarding the reproductive behaviour in this population and support the hypothesis that females adjust their choosiness in relation to male availability. Two-spotted goby, sexual selection, female choosiness, seasonal changes