Male harassment reduces short-term female fitness in guppies.

Males can maximise their fitness by copulating with as many females as possible. Although this behaviour may have negative consequences for the females involved, females can also benefit from multiple mating. For example, multiple mated female guppies produce more, larger and fitter offspring. It is not clear if these fitness benefits are a direct result of multiple mating, or the product of female choice - either pre or post copulatory - for better quality males. To answer this question, individual virgin female guppies were exposed to different combinations of males: just one male; three males, one at a time; and three males presented simultaneously. Mating activity was more intense in the three-at-a-time treatment but did not differ between the other two. This increased attention did not affect gestation time nor offspring size, but significantly reduced the number of offspring produced. This reveals that male harassment causes a direct reduction in female short-term fitness.