Sexual Competition, Coercive Mating and Mate Assessment ... - CPRG

970 A. Bisazza, S. Manfredi & A. PilastroIn the replicates with two females, females showed little tendency to shoal andduring 79.1 ‹ 7.8% (range 70±93.3%) of the observation periods they were swimmingin two di€erent squares of the grid and were usually followed by one male ata time. Fights between males occurred almost exclusively when both males werefollowing the same female. Large males still made signi®cantly more attacks thansmall ones (Table 1). There was a tendency for reduced aggressiveness of the smallmales in trials with two females but the di€erence was non-signi®cant (z ˆ 1.48, pˆ0.15, n ˆ 14, Mann±Whitney test). With a 1 : 1 sex ratio, the number of matingattempts carried out by the small male was nearly identical to that performed bythe large male (Table 1). The proportion of mating attempts carried out by thelarge male in these replicates was signi®cantly lower than that observed in thereplicates with two males and one female (t ˆ 3.76, p ˆ0.001, n ˆ 33). Large malesdid most of their mating attempts with the large female, whereas small males didmost of their mating attempts with the small female (repeated measure ANOVA, Fˆ 58.3, df ˆ 3,39, p