Gray Seal Facts

Scientific Name: Halichoerus grypus

Gray seal and pup
Gray seal and her pup.

Westend61 / Getty Images

The gray seal (Halichoerus grypus) is an earless or "true seal" found along North Atlantic coasts. It is called the gray seal in the United States and the grey seal elsewhere. It is also called the Atlantic seal or the horsehead seal, for the male's distinctive arched nose.

Fast Facts: Gray Seal

  • Scientific Name: Halichoerus grypus
  • Common Names: Gray seal, grey seal, Atlantic seal, horsehead seal
  • Basic Animal Group: Mammal
  • Size: 5 feet 3 inches - 8 feet 10 inches
  • Weight: 220-880 pounds
  • Lifespan: 25-35 years
  • Diet: Carnivore
  • Habitat: North Atlantic coastal waters
  • Population: 600,000
  • Conservation Status: Least Concern

Description

Like other earless seals (family Phocidae), the gray seal has short flippers and lacks external ear flaps. Mature males are much larger than females and have a different coat color. Males average around 8 feet long, but may grow to over 10 feet in length. They weigh up to 880 pounds. Males are dark gray or brownish gray with silver spots. The species' scientific name, Halichoerus grypus, means "hook-nosed sea pig," and refers to the male's long arched nose. Females range from around 5 feet 3 inches to 7 feet 6 inches in length and weigh between 220 and 550 pounds. They have silver-gray fur with dark scattered spots. Pups are born with white fur.

Gray seal bull
The gray seal bull has a distinctive horsehead face. Noemi De La Ville / 500px / Getty Images

Habitat and Distribution

Gray seals live in the North Atlantic Ocean. There are three large gray seal populations and numerous smaller colonies. The species occurs in great numbers in the coastal waters of Canada south to Massachusetts (with sightings in Cape Hatteras, North Carolina), the Baltic Sea, and the United Kingdom and Ireland. The seals are most often seen when they haul out in winter. They frequent rocky coasts, icebergs, sandbars, and islands.

Gray seal distribution map
Gray seal distribution. Darekk2 using IUCN Red List data / Creative Commons Attribution-Share Alike 4.0 International license

Diet

Seals are carnivores. Gray seals eat fish, squid, octopuses, crustaceans, porpoises, harbor seals, and seabirds. Mature males (bulls) will kill and cannibalize pups of its own species. Gray seals can dive for as long as an hour at depths up to 1,560 feet. They use sight and sound to hunt their prey.

Behavior

For most of the year, gray seals are solitary or live in small groups. During this time, they rest in open water with only their head and neck exposed to air. They gather on land for mating, pupping, and molting.

Reproduction and Offspring

Males may breed with several females during the mating season. Gestation lasts 11 months, resulting in the birth of a single pup. Females give birth in March in the Baltic, from December to February in the western Atlantic, and from September to November in the eastern Atlantic. Newborn pups have white fur and weigh around 25 pounds. For 3 weeks, the female nurses her pup and does not hunt. Males do not participate in pup care but may defend females from threats. After this time, the pups molt into their adult coats and head to the sea to learn to hunt. Pup survival rate ranges from 50-85%, depending on weather conditions and prey availability. Females become sexually mature at 4 years of age. Gray seals live between 25 and 35 years.

Conservation Status

The IUCN classifies the gray seal conservation status as "least concern." Although the species was nearly extirpated in the mid-20th century, it began to recover in the 1980s following the passage of the 1972 Marine Mammal Protection Act in the United States and the Conservation of Seals Act 1970 in the United Kingdom (which does not apply to Northern Ireland). Gray seal population size has continued to increase. As of 2016, the population was estimated to be 632,000 gray seals. Some fishermen have called for a cull, believing high seal numbers are at least partly responsible for low fish stocks.

Threats

Gray seals are legally hunted in Sweden, Finland, and the Baltic Sea. Risks to the seals include entanglement in fishing gear, by-catch, collision with ships, pollution (especially PCBs and DDT), and oil spills. Climate change and severe weather also affect the seals and their prey.

Gray Seals and Humans

Gray seals do well in captivity and are commonly seen in zoos. They were traditionally popular in circus acts. According to Scottish scholar David Thomson, they gray seal was the basis of the Celtic seal legend of the selchie, a creature that could assume human and seal form. While gray seals frequent inhabited areas, people are advised to avoid feeding or harassing them, as this alters seal behavior and ultimately endangers them.

Sources

  • Ailsa j, Hall; Bernie j, Mcconnell; Richard j, Barker. "Factors affecting first-year survival in grey seals and their implications for life history strategy." Journal of Animal Ecology. 70: 138–149, 2008. doi:10.1111/j.1365-2656.2001.00468.x
  • Bjärvall, A. and S. Ullström. The Mammals of Britain and Europe. London: Croom Helm, 1986.
  • Bowen, D. Halichoerus grypus. The IUCN Red List of Threatened Species 2016: e.T9660A45226042. doi:10.2305/IUCN.UK.2016-1.RLTS.T9660A45226042.en
  • Bowen, W.D. and D.B. Siniff. Distribution, population biology, and feeding ecology of marine mammals. In: J.E., Reynolds, III and S.A. Rommel (eds), Biology of Marine Mammals, pp. 423-484. Smithsonian Press, Washington, D.C.. 1999.
  • Wozencraft, W.C. "Order Carnivora". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press, 2005. ISBN 978-0-8018-8221-0.