The reproductive behavior and energetics of male gray seals (Halichoerus grypus) breeding on a land-fast ice substrate

Abstract

The reproductive behavior of male gray seals (Halichoerus grypus) breeding on land-fast ice at Amet Island, Nova Scotia, was studied. Data on energy expenditure (rate of mass loss over time) were collected. The average time budget of males at Amet Island was comparable to that of land-breeding males. The behavior of males showed seasonal changes, with a decrease in the proportion of time spent in the water and an increase in agonistic behavior during the peak mating period. The estimated amount of body mass lost over the season ranged between 25.6 and 77.1 kg, and the estimated percent of initial body mass lost ranged between 7.7 and 26.5% (n=10). The maximum number of observed copulations for an individual male was nine. Only 15 out of 42 males observed during 1992 and 1993 were seen copulating. The number of observed copulations per male was strongly correlated with success in remaining close to, or attending, females (r=0.91, P<0.001, n=42). The mean duration of attendance was 4.5 ± 5.54 days (n=42). Large size was not an important factor in determining attendance success, but reproductive effort (the estimated proportion of body mass lost over the season) and success in agonistic interactions with other males were both correlated with male success.