Reproduction in the crabeater seal probably takes place on the pack ice surrounding Antarctica in the austral spring, from October to December (Kooyman 1981). Starting in September, a pregnant female occupies a space on the ice floe in which she gives birth and cares for her single pup. A male joins the female in her chosen area just before or just after parturition. He defends the female and the newborn pup. He is, in all likelihood, not the father of the pups. Females come into estrus just after weaning and Siniff et al. (1979) report that the male's only apparent interest is in waiting for the female to be sexually receptive. Males aggressively defend females from other intruding males. It is not clear if the males join the females because of a female cue such as scent or because of the pup.
Mating System: monogamous
Pups are born weighing approximately 20 kg and gain weight while nursing at about 4.2 kg/day (Shaughnessy and Kerry 1989). Physical contact between the mother and pup during this period is necessary. If either the pup or the mother strays, the other immediately follows. Pups are weaned at about 3 weeks old. It is unclear if physical mechanisms in the mother, such as reduced milk production, cause the weaning or if the defending male drives the pup and mother apart. Throughout the lactation period the male is aggressive towards the female. She defends herself by biting him on the neck and sides. By the end of lactation her body weight may be reduced by half, so she would be unable to defend herself adequately. She becomes sexually receptive shortly after weaning and, unlike most seals, copulation appears to occur on the ice floes instead of in the water (Shaughnessy and Kerry 1981; Siniff et al. 1979)
Gestation lasts about 11 months and probably includes a period of delayed implantation (Nowak 1997). Crabeater seals become sexually mature between 3 and 4 years of age and females may have successful pregnancies between 5 and 25 years old (Bengston and Siniff 1981).
Breeding season: Reproduction in the crabeater seal probably takes place on the pack ice surrounding Antarctica in the austral spring, from October to December.
Average number of offspring: 1.
Average gestation period: 11 months.
Average weaning age: 3 weeks.
Average time to independence: 3 weeks.
Range age at sexual or reproductive maturity (female): 3 to 4 years.
Range age at sexual or reproductive maturity (male): 3 to 4 years.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous ; delayed implantation
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
- Bengston, J., B. Stewart. 1992. Diving and haulout behavior of crabeater seals in the Weddell Sea, Antarctica, during March 1986.
- Kooyman, G. 1981. Crabeater Seal Lobodon carcinophagus. Pp. vol 2: 221-235 in S Ridgeway, R Harrison, eds. Handbook of Marine Mammals. London: Academic Press.
- Nowak, R. 1997. "Walker's Mammals of the World 5.1 (online): John's Hopkins University Press" (On-line). Accessed May 31, 2002 at http://www.press.jhu.edu/books/walker/.
- Shaugnessy, P., K. Kerry. January 1989. Crabeater Seals Lobodon carcinophagus during the breeding season: observations on five groups near enderby land, Antarctica. Marine Mammal Science, 5(1): 68-77.
- Siniff, D., I. Stirling, J. Bengston, R. Reichle. 1979. Social and reproductive behavior of crabeater seals (Lobodon carcinophagus) during the austral spring. Canadian Journal of Zoology, 57: 2243-2256.