Parental Care

 

Parental care in all pinniped seals is exclusively the task of the female. Females invest in their young primarily by milk production, but also through defense of the young and the energy requirements of pregnancy (Lydersen and Kovacs, 1999). Most pups are born from mid-March to May on exposed ice floes (Burns, 1967). Pups are born during this season probably because it is the most favorable time of year for weather, ice, and feeding conditions (Burns, 1967). In a study of birth sites by Kovacs et al. (1996) all birth sites where the young survived more than 48 hrs were less than one meter from the water. Ice floes are probably utilized because of the presence of predators on the mainland and the terrestrial immobility of seals because they have limbs adapted for swimming (Harrison et al. 1968). The sex ratio of pups at birth is essentially equal.
Growth and Development
Bearded seals have precocial young (Lydersen and Kovacs, 1999). Pups are born with their eyes open, and are able to vocalize, move around, and suckle within minutes of birth (Lydersen and Kovacs, 1999). Pups can usually enter the water and swim a few hours after that (Lydersen et al. 1994). Pups probably enter the water shortly after birth to prevent predation by moving away from the sight and smell of the birth blood (Lydersen and Kovacs, 1999, Kovacs et al. 1996). Bearded seal pups are born with a body mass of 29-43 kg at birth (Lydersen et al. 1994) and gain weight rapidly as they build fat/blubber. This quick growth rate could be partially caused by the high fat content (up to 53%) of the mother’s milk (Burns, 1967) which is provided to the pups by the nursing mother once about every 3 hrs (Kovacs et al. 1996). This high fat content is also a high drain on the female, causing them to lose body weight rapidly (Burns, 1967, Atkinson, 1997). The pups are also born with dense natal hair which is important for warmth. Most moms nurse their pup for 12-18 days (Rearden, 1981, Stirling and Thomas, 2003) and in bearded seals weaning is more gradual than other phocid seals, being completed about 24 days after birth. (Gjertz et al. 2000, Lydersen and Kovacs, 1999). Toward the end of lactation pups start to eat some solid food as indicated by investigations of their stomach contents (Lydersen et al. 1994).
Image Courtesy of David Rugh - National Marine Mammal Laboratory  

Juvenile Behavior
During the pup’s dependency period they split their time equally between being hauled-out on the ice and being in the water with their mother (Lydersen et al. 1994). When hauled-out, pups are usually not more than one body length away from the water and always lay at the edge of the ice facing the water (Lydersen and Kovacs, 1999). When the pups are in the water they also split their time equally between time spent submerged and time spent at the surface. Most of the pups’ dives are shallow and of short duration but diving skills also increase significantly with age (Lydersen et al. 1994). Also, the bearded seal evolved under significant predation pressure from polar bears and therefore pups might have needed to develop swimming and diving skills at a very early age (Lydersen et al. 1994).

Image courtesy of NOAA, Photographer: Captain Budd Christman, NOAA Corps. Taken May 1979 in the Bering Sea.
Maternal Behavior
When with pups, female bearded seals alter their activities to take care of their pups. In a study done by Krafft et al. (2000) the female seals with pups only spent 8% of their time hauled-out and 92% of their time in the water. Most of the time spent out of the water was assumed to be time spent nursing. But by minimizing their time hauled-out mother-pup pairs could be less conspicuous to surface predators. Of the time spent in the water it was divided equally between being on the surface and time spent submerged, which could be a compromise between feeding and attending the pup. Much of this time in the water was spent in maternal care, being with and taking care of their pup. Most dives the mothers performed were U-shaped dives, thought to be foraging dives. From these dive profiles and stomach contents, this study showed that bearded seal mothers forage during the lactation period, even though they are still losing weight. This weight loss and foraging behavior is probably because the energy expenditure required to produce a weaned pup is extremely high, too high for the seals to produce successful offspring without foraging themselves during this time.