Seals and East Coast

Harbor Seals

General Description and Status
Harbor seals, Phoca vitulina concolor, are the most abundant pinniped species off the eastern coast of the United States. Their maximum length is nearly 6 feet. Harbor seals are recognized by their short, concave snout, giving them a profile shaped much like the head of a dog. Approximately 4,000-4,500 harbor seals are believed to overwinter in southern New England (Payne and Selzer 1989).

Distribution and Abundance
Harbor seals range from Labrador to Long Island, New York with occasional sightings as far south as South Carolina and Florida (Brimley 1931, Caldwell and Caldwell 1969, Payne and Selzer 1986). This species previously bred as far south as Cape Cod during the first part of the twentieth century (Katona et al. 1993). However, their breeding range and seasonal distribution have changed over time which has most likely been a direct result of a state-offered bounty in effect in Massachusetts from the late 1800's until 1962 (Payne and Selzer 1989). Since the enactment of the Marine Mammal Protection Act in 1972, harbor seals have more than doubled their numbers in southern New England (Payne and Schneider 1984).

In southern New England, harbor seals occur mainly from late September through May (Schneider and Payne 1983). Following May, they move northward and are found along the coast of Maine and eastern Canada (Whitman and Payne 1990). By the end of November, many seals leave their more northern habitats with great numbers traveling to the Cape Cod area (Katona et al. 1993). Harbor seals are abundant in the waters off Cape Cod during the winter and spring (Payne and Selzer 1989) although periodic sightings also occur in the summer and fall (Center for Coastal Studies, unpublished data).

Feeding
Analyses of fecal samples from harbor seals indicated that the main prey item for this species in the Cape Cod area is sand lance, Ammodytes (spp.) (Payne and Selzer 1989). Overall, though, harbor seals are considered to be opportunistic feeders and tend to forage on fish and squid species that are regionally and seasonally abundant, showing a preference for small schooling fishes (Payne and Selzer 1989).

Reproduction
Presently in New England, no pupping ledges are known to exist south of Maine (Payne and Selzer 1989). Adult females commonly pup in the same area in which they were born. Pups are born from mid-April to mid-June and generally, are weaned within 4 to 6 weeks (Wilson 1978). Shortly after weaning, females will mate again. Both sexes are thought to reach sexual maturity by the age of 6 (Boulva and McLaren 1979). Segregation by both sex and age class has been reported at haul-out sites during the breeding season in many locations (see Kovacs et al. 1990). However, along the beaches of Sable Island, Nova Scotia, there was no evidence of segregation by age, sex or breeding condition (Godsell 1988). Breeding males are known to display while in the water which may be attributed to territory defense or possibly self-advertising (Perry et al. 1993), although Godsell (1988) found that such displays or fights did not appear to influence male haul-out patterns.

Group Size and Composition
Little information exists regarding the social structure or group composition of harbor seals in the Cape Cod region. According to Whitman and Payne (1990), younger seals appear to occupy mainly the outer parameters of breeding areas and they found that, in the waters surrounding Cape Cod, 95% of the seals were juveniles (less than 1 year) and subadults (less than 4 years). Data on harbor seals inhabiting rock haul-out sites indicate that they create hierarchies based on size and sex with territorial adult males dominating all other sex and age classes while protecting their preferred sites (Sullivan 1982). Whitman and Payne (1990) reported that dominant males appeared to displace subadults of both sexes on rock haul-out sites after weaning occurs and competition for receptive females begins to increase. This displacement of subordinate subadults and juveniles may explain somewhat their great abundance in the Cape Cod area.




Grey Seals
General Description and Status


Grey seals, Halichoerus grypus, are the largest seals seen in the Stellwagen region with any frequency. They reach up to 8 feet in length and are most often recognized by their long, straight snout which gives them a horse-shaped head. A frontal view of the nostrils reveals a "W" shape unlike the "V" shape appearance of the harbor seal. There are no current population estimates for grey seals in the Gulf of Maine but their numbers appear to be increasing.

Distribution and Abundance
The western North Atlantic grey seal ranges from the Labrador coast southward to Nantucket with the main concentration found around the Gulf of St. Lawrence (Bonner 1990). In the early 1960's, the Massachusetts population of grey seals was thought to number around 20 animals as a result of bounty hunts (Shurman 1986). Presently, that remnant population is located southwest of Nantucket Island and is the only active breeding colony off the eastern coast of the United States (Payne and Selzer 1986). In recent years, sightings of grey seals in Massachusetts waters (including the Stellwgen Bank region) have become more frequent which is probably due to animals
immigrating from the expanding Canadian stock (Katona et al. 1993). The majority of grey seal
sightings in Cape Cod Bay and the Stellwagen Bank area occur during the winter and spring, although periodic sightings have been recorded in the summer (Center for Coastal studies unpublished data).

Feeding
Grey seals prey mostly on fish but will also forage on invertebrates (Katona et al. 1993). In the Nantucket area, grey seals are thought to feed on skates, Raja spp., alewife, Alosa pseudoharengus, and sand lance, Ammodytes spp. (Shurman 1983).

Reproduction
In the northwest Atlantic, pups are born in January and February, either on land or on ice (Bonner 1990). Nursing lasts for 2 to 3 weeks and breeding occurs shortly after weaning (Bonner 1990, Katona et al. 1993). Data from Sable Island, Nova Scotia, suggest that females return to the same beach area to pup from year to year (Bones and James 1979). Bones and James (1979) also reported that males did not appear to defend territories or form dominance hierarchies but instead competed for the right to stay within the aggregation of receptive females. Males that failed to establish themselves with receptive cows tried to intercept females returning to the sea at the end of the breeding season, but appeared not to be as reproductively successful. Studies of grey seals around Great Britain indicate that both sexes exhibit fidelity to previous breeding sites (Amos et al. 1993, Twiss et al. 1993). Amos and others (1993) found that 30% of pups born to the same female in different years were full siblings, which may be partly due to this high degree of site fidelity. Amos and others (1993) also reported that this species breeds colonially in remote areas around the British Isles and that males compete aggressively for receptive females and even though the dominant males are generally more successful, subordinate males do gain some access to females. This was attributed to subordinates either being able to "sneak" access to females or, perhaps, that some females are fertilized outside of the breeding colony.

Group Size and Composition
Information regarding the social structure or group composition of grey seals in the Cape Cod area is not available.