|Gray Seal Halichoerus grypus
Common Names: Horsehead Seal, Horseface Seal, Horsey Seal
Halichoerus grypus is a large seal with a distinctive long, broad, prominently bridged snout, which has lead to the common name of ‘horsehead’ or ‘horseface’ seal. The scientific name, Halichoerus grypus, can be translated to mean “hooknosed pig of the sea”. While the adult coat colouration is variable, it is generally bolder and more prominently spotted than the Harbour Seal. The male coat is typically a dark silver or gray colour with black blotches on the back, while the ventral side and head are usually slightly lighter. The female coat is even lighter in colouration, being light gray or tan on the dorsal side with dark overlying spots, and white or silver on the stomach. At birth the pups have a long, white coat or lanugo, but after a period of three to four weeks, the young animals moult and assume a gray, spotted juvenile coat. The male seals or bulls moult annually between February and May, at which time they lose and renew their fur and part of the epidermis, while the females moult slightly earlier from January to April. The adult males may reach a maximum length of 300 cm and a weight of 362 kg, while the females are slightly smaller and generally do not exceed lengths of 230 cm and weights of 181 kg.
Geographical Distribution and Habitat Requirements:
The gray seal inhabits the temperate waters of the North Atlantic, and the global population is approximately 135,000, half of which are found in the British Isles. Globally, they are occur in the waters around Norway, the White and Baltic Seas and Iceland. In regards to the Canadian distribution of Halichoerus grypus, significant numbers can be found in the Gulf of St. Lawrence, where ice breeding commonly occurs in the Northumberland Strait, George Bay, and the Magdalen Islands. Beyond the gulf, the species can be found primarily in Nova Scotia on both Basque and Sable Island, and less frequently on the eastern coast of the province. They have been observed around both Newfoundland and Prince Edward Island, and around Grand Manan Island in New Brunswick on the Bay of Fundy. I have personally observed the gray seal off the southern tip of Campobello Island, N.B. on a small rocky island know as Boring Stone that is only visible at low tide. Halichoerus grypus frequently inhabits such skerries exposed at low tide, as well as exposed rocky coasts and remote islands in temperate seas. The habitats that this species prefers are those that are remote and found in areas with rough seas and strong rip tide currents.
While the young seals disperse widely in the first few years of their lives, the adult gray seal is typically sedentary about the vicinity of its breeding colonies. Colonies are known to range in size from 100 to almost 9,000 individuals. This species employs group foraging, and leave the water to form dense colonies when moulting and breeding. The breeding season itself varies greatly with the geographical location of the colony. The species is extremely territorial during the breeding season, with the female defending the area immediately around the calves and the males defending the entire breeding area. The older males establish breeding areas on rocky beaches or ice shelves, and within a particular breeding area there can typically be found a harem of 6 to 10 females with their respective calves. The bull challenges intruders with displays of aggression that include a lowered head, hissing noises and a shuffling charge. If the intruder does not withdraw, the two animals will engage in a physical confrontation in which the individuals grapple with one another’s necks. It is usually the invader that will ultimately retreat, and the victorious bull will give a celebratory roll. In the Baltic Sea and the Canadian shores, mating occurs on ice or rocky shores in January and February. In the British Isles, mating occurs on rocky islands from September to December. It is usually single births that occur, and the pup is nursed for a period of 16 to 18 days. After the pups have moulted, the mothers desert their young and return to the water. The young animals then enter the water themselves and usually disperse elsewhere. Sexual maturity is reached at the age of six or seven years.
Gray seals often employ deep diving when foraging, and are known to remain under water for periods of up to 20 minutes and reach extreme depths of 200m. Deep diving adaptations include extreme bradycardia, increased oxygen stores, peripheral vasoconstriction and anaerobic metabolism in their peripheral tissues. Halichoerus grypus is carnivorous and typically feeds on benthic fish such as rockfish, saithe, pollack, cod, flounder, whiting, coal fish, and ling and to a lesser degree on squid, pelagic crustacea, and schooling fish such as herring and salmon. Aside from human hunting, the killer whale is the main predator of the gray seal. Gray seals, like other pinnipeds, are intelligent and have well developed senses. They have good vision underwater, functional vision in air and it is adaptable to the darkness of ocean depths. Hearing is acute both above and below the water’s surface. Although first year mortality is 50% in the gray seal, males that survive the first year typically live to an age of 35 years and females to 45 years. Competition amongst males may contribute to their shorter life span. The gray seal is active all year
and hibernation does not occur.
While large scale commercial hunting of the Gray Seal has not occurred in several years, the Nova Scotian Sealer’s Organization is seeking permission to slaughter 25,000 animals over the next three years in order to market the seal products. The Canadian government also announced in January 1999, that they have granted permission for the hunting of several hundred seals in areas other than Sable Island. Gray seals are highly unpopular with fisherman as they often consume commercial fish such as salmon, and they have been known to damage fishing nets and traps. They also act as the terminal host for codworm, and it is the intermediate stage of the codworm that encysts in the flesh of cod. The shooting of seals to prevent the damage of nets and traps is legal in many countries, but attempts are being made to encourage the use of less severe methods such as anti-predator nets to deter the gray seal. Marine pollution poses a significant threat to gray seal survival as the animal’s respiration can be affected by organochlorines and oil spills in the water. Although the gray seal is not considered to be critically endangered by the IUCN, it is listed as being an endangered species in the Baltic Sea region where populations have been greatly declined by hunting, disturbance, marine entanglement and pollution. The population of gray seals in this region at one time numbered well over 100,000 but over the years it has been reduced to critical levels. Hunting of the gray seal in the Baltic region was banned in 1988, but there has been mounting pressure from Finland to lift this ban. This pressure exits despite the publication of a study in 1997 that indicated that the level of hunting that the Baltic Sea population could reasonably sustain was close to zero! Studies have also been done on the use of immunoconception in gray seals in order to “manage” the increasing wild populations by inhibiting or greatly reducing the conception and birth of new pups. While the Western Atlantic populations of the gray seal are not presently endangered, one has to wonder what may become of Halichoerus grypus in several years if the intentional eradication of the species continues.