Female fifteen-spined sticklebacks prefer better fathers.

We studied how male fifteen-spined sticklebacks, Spinachia spinachia, vary in paternal competence, whether males advertise their competence and whether females prefer better fathers. In this species the male alone provides care for the offspring through nest building, fanning, cleaning and protecting the eggs. We found no female preference for larger males. Instead, females preferred males that during the subsequent paternal phase fanned their nests in shorter fanning bouts. Such males enjoyed a significantly higher hatching success because they fanned more often than males with longer fanning bouts. Males that fanned for short bouts during the paternal phase were also able to increase their fin beat rate. Frequent fanning and high fin beat rates may improve the flow of oxygen to the eggs. Beat rate may be a condition-dependent trait, because males that lost more weight were unable to increase their fin beat rate. During courtship, males perform behaviours such as displacement fanning and body shaking. Females preferred males showing more frequent body shakes during courtship. Body shake frequency correlated positively with hatching success, and negatively with mean fanning bout duration during the paternal phase. The results indicate that female S. spinachia show a preference for direct benefits in terms of better paternal care, and that males may signal this ability to females by shaking their body during courtship. Copyright 1998 The Association for the Study of Animal Behaviour.