Nj. Lunn et al., REPRODUCTIVE-PERFORMANCE OF FEMALE ANTARCTIC FUR SEALS - THE INFLUENCE OF AGE, BREEDING EXPERIENCE, ENVIRONMENTAL VARIATION AND INDIVIDUAL QUALITY, Journal of Animal Ecology, 63(4), 1994, pp. 827-840
1. The reproductive performance of female Antarctic fur seals was exam
ined in relation to age, reproductive experience and environmental var
iation over 10 consecutive years (1983-92) at Bird Island, South Georg
ia. 2. The age at which females first gave birth varied from 3 to 6 ye
ars; over 90% of these females were 3 or 4 years of age. We found no e
vidence to suggest that age at primiparity had significant effects on
subsequent reproduction; however, 3-year-old primiparae were less like
ly to be seen in subsequent years than 4-year-old primparae which may
indicate a cost, in terms of survival, for females that first give bir
th at an early age. 3. Age-specific reproductive rates increased rapid
ly from ages 2 to 6 years, reached a peak of 0.80 at 7-9 years, remain
ed above 0.75 until 11 years and then began to decline with increasing
age. 4. The mean duration of foraging trips in the current year (whic
h was used as a measure of the availability of food resources) consist
ently improved models of the likelihood of pupping and of weaning succ
ess. When these trips were long (indicating reduced local food resourc
es), females returned to the breeding beaches later, fewer females pup
ped, they gave birth to lighter pups and weaning success was reduced.
5. The reproductive performance of older, experienced Antarctic fur se
als was greater than that of younger, inexperienced animals because th
ey had higher natality rates, gave birth to heavier pups earlier in th
e season, had greater weaning success and were more likely to pup the
next season.