Phenotype and mating success of male harbour seals, Phoca vitulina, at Sable Island, Nova Scotia.
Date
1997
Authors
Coltman, David W.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Reproductive behaviour and mating success of male harbour seals (Phoca vitulina) were studied at Sable Island, Nova Scotia, between 1992 and 1995. Individually marked males were fitted with time-depth recorders to monitor their activity at sea. Males were also given deuterium labelled water to estimate body composition and energy expenditure during the breeding season. These studies showed reproduction to be as energetically costly for male harbour seals as it is for males of other species. Due to small body size, most male harbour seals cannot energetically afford the extended fast which is characteristic of other breeding pinnipeds, hence they forage during deep diving bouts until females are likely to become receptive. All males changed their diving behaviour during the mating period such that repeated bouts of shallow diving activity, which reflect reproductive behaviour, predominated.
Mating success was estimated using microsatellite markers to analyze paternity genetically. The paternity analysis of two cohorts of pups indicated that harbour seals are polygynous, as the most successful male harbour seals may sire as many as 6 pups in a season, but the variance in mating success among males was low, with most males likely to have sired one or no pups. This is consistent with the limited ability of males to monopolize females in the aquatic mating environment, and with the dispersal of females at sea near Sable Island. Females may mate with males from any stretch of the island.
Male mating success could not be reliably predicted from any single phenotypic characteristic, however, multivariate analysis identified suites of characteristics which are associated with varying degrees of reproductive success. Relatively large males which hauled out alone and bore wounds from fighting were reproductively unsuccessful, and likely represent individuals who have been defeated in intrasexual competition. The group of males with the highest rate of mating success tended to have the greatest energy stores at the beginning of the mating season, and they started to compete for mates earlier and at greater energetic expense than other males.
Thesis (Ph.D.)--Dalhousie University (Canada), 1997.
Mating success was estimated using microsatellite markers to analyze paternity genetically. The paternity analysis of two cohorts of pups indicated that harbour seals are polygynous, as the most successful male harbour seals may sire as many as 6 pups in a season, but the variance in mating success among males was low, with most males likely to have sired one or no pups. This is consistent with the limited ability of males to monopolize females in the aquatic mating environment, and with the dispersal of females at sea near Sable Island. Females may mate with males from any stretch of the island.
Male mating success could not be reliably predicted from any single phenotypic characteristic, however, multivariate analysis identified suites of characteristics which are associated with varying degrees of reproductive success. Relatively large males which hauled out alone and bore wounds from fighting were reproductively unsuccessful, and likely represent individuals who have been defeated in intrasexual competition. The group of males with the highest rate of mating success tended to have the greatest energy stores at the beginning of the mating season, and they started to compete for mates earlier and at greater energetic expense than other males.
Thesis (Ph.D.)--Dalhousie University (Canada), 1997.
Keywords
Biology, Genetics., Psychology, Behavioral., Biology, Zoology.