DOES MALE HARASSMENT OF FEMALES CONTRIBUTE TO REPRODUCTIVE SYNCHRONY IN THE GREY SEAL BY AFFECTING MATERNAL PERFORMANCE

We investigated the possibility that male harassment of lactating fema les differed in relation to time of birth in the grey seal, Halichoeru s grypus, on Sable Island, Nova Scotia. This was done by comparing the frequency of male disturbances, maternal performance and pup growth f or females that either gave birth during the peak of the pupping seaso n or after the peak. Of the females, 58% gave birth in a 7-day period near the beginning of the pupping period, when the operational sex rat io was 2-4 females per male. Late in the pupping period the operationa l sex ratio reversed to about 1 female for every 2 males. The relative frequency of disturbances by males was significantly greater for late -pupping mothers than for peak-pupping ones (1.9 vs. 1.4 encounters/h) . Females that gave birth late also were disturbed by males 3 times mo re often than females that gave birth during the peak (3.4 vs. 1.1% of observation time). Late-pupping mothers spent 22% less time suckling (4.0 vs. 5.1% of observation time), had 30% slower growing pups (1.7 v s. 2.4 kg/d), and weaned pups that were 16% lighter (45.6 vs. 54.0 kg) . The effect of birth time on pup mass gain and weaning mass was not a ttributable to factors such as maternal mass, pup birth mass or pup se x. We conclude that the reduced maternal performance is likely the res ult of the increased male harassment. As reduced weaning mass can lead to reduced juvenile survival, male harassment may have contributed to the enhanced reproductive synchrony in this species.