About the Species
Gray seals are found in coastal waters throughout the North Atlantic. They are sometimes called "horseheads" (adults males in particular have large, horse-like heads) because of their large, curved noses.
Gray seals gather in large groups during the mating/pupping, and molting seasons. Outside of the mating/pupping season, they often share their habitat with harbor seals.
Gray seals, like all marine mammals, are protected under the Marine Mammal Protection Act. NOAA Fisheries is committed to conserving and protecting gray seals. Our scientists and partners use a variety of innovative techniques to study, learn more about, and protect this species.
To manage gray seals in U.S. waters, we have grouped them into a western North Atlantic stock. Our scientists are not currently able to estimate the number of seals in this stock.
Learn more about our estimates for population size in our stock assessment reports.
- Throughout Its Range
Gray seals are part of the "true” seal family. All true seals have short flippers, which they use to move in a “caterpillar”-like motion on land. They do not have external ear flaps.
Female gray seals are about 7.5 feet long and weigh about 550 pounds, while males are about 10 feet long and weigh about 880 pounds. Females have silver-gray fur with scattered dark spots, while males have dark gray fur with silver-gray spots. Males also have longer noses than females. The male nose is so distinctive that the gray seal’s scientific name, Halichoerus grypus, means "hooked-nosed pig of the sea."
Gray seal pups have white fur known as lanugo. This white fur helps absorb sunlight and trap heat to keep the pups warm. The lanugo is also related to their evolutionary history with other ice-breeding seals. Gray seals breed on ice in part of Canada (Gulf of St. Lawrence) and the Baltic Sea. Pups shed their lanugo when they are about 3 weeks old.
Behavior and Diet
Gray seals gather in large groups during the mating/pupping and molting seasons. During the rest of the year, they are usually found alone or in small groups. Only their head and neck are above the surface when they rest in open waters.
Gray seals can dive up to 1,560 feet below the surface for as long as 1 hour. They eat 4 to 6 percent of their body weight in food each day, but they do not eat during the mating/pupping or molting seasons. These seals are effective hunters because they have excellent vision and hearing. They often hunt in groups, which makes it easier for them to catch their prey. They eat fish, crustaceans, squid, octopuses, and sometimes even seabirds.
Where They Live
Gray seals are found across the North Atlantic in coastal areas from New York to the Baltic Sea. There are three stocks of gray seals worldwide: the western North Atlantic stock (eastern Canada and the northeastern United States), the eastern North Atlantic stock (Great Britain, Iceland, Norway, Denmark, the Faroe Islands, and Russia), and the Baltic Sea stock.
On land, gray seals are found on rocky coasts, islands, sandbars, ice shelves, and icebergs. They share their habitat with many other species and often live in the same areas as harbor seals.
Lifespan & Reproduction
Gray seals live for 25 to 35 years. They gather in large groups to mate. Males that breed on land can mate with many different females in a single breeding season.
Females are pregnant for about 11 months and give birth to a single pup. Females in the eastern Atlantic Ocean give birth from September to November, while females in the western Atlantic Ocean give birth from December to February. Females in the Baltic give birth in March.
At birth, newborn gray seals weigh about 35 pounds. They nurse on high-fat milk for about 3 weeks. During this time, they gain about 3 pounds per day and develop a thick blubber layer.
Gray seal pups are very vocal. Their cries sometimes sound like a human baby crying. This is normal behavior that helps mothers find their pups when they return to the shore from foraging. Moms don’t feed while nursing the pups, but they do use vocalizations to find pups on a crowded beach.
Gray seals can become entangled in fishing gear and other types of marine debris, either swimming off with the gear attached or becoming anchored. They can become entangled in many different gear types, including gillnets, trawls, purse seines, or weirs. Once entangled, seals may drown if they cannot reach the surface to breathe, or they may drag and swim with attached gear for long distances. This can ultimately result in fatigue, compromised feeding ability, or severe injury, which may lead to reduced reproductive success and death.
Gray seals are easy to view in the wild, but this puts them at higher risk of human-related injuries and death. Feeding (or trying to feed) them is harmful and illegal, because it changes their natural behaviors and makes them less wary of people and vessels. They learn to associate humans with an easy meal and change their natural hunting practices—for example, they take bait catch directly off fishing gear. Sometimes they fall victim to retaliation (such as shooting) by frustrated boaters and fishermen.
They may also be disturbed or harassed by the presence of humans and watercraft. Harassment is illegal and happens when any act of pursuit, torment, or annoyance might injure them or disrupt their behaviors. Remember to share the shore with gray seals for their safety and yours.
Contaminants enter ocean waters from many sources, including oil and gas development, wastewater discharges, urban runoff, and other industrial processes. Once in the environment, these substances move up the food chain and accumulate in predators near the top of the food chain such as gray seals. These contaminants accumulate in gray seals’ blubber stores, threatening their immune and reproductive systems.
Oil spills and energy exploration
Oil spills can harm gray seals. If exposed to oil, a gray seal’s fur can no longer repel water. This makes it difficult for the seal to swim, float, and keep warm. Inhaling or swallowing oil can also damage a seal’s respiratory, digestive, reproductive, and central nervous systems. Oil can also irritate or burn the seal’s skin.
Inadvertent vessel strikes can injure or kill gray seals. Gray seals are vulnerable to vessel collisions throughout their range, but the risk is much higher in some coastal areas with heavy ship traffic.
Gray seals, like all marine mammals, are protected under the Marine Mammal Protection Act. In the United States, NOAA Fisheries works to protect all gray seals.
Reducing Vessel Strikes
Collisions between gray seals and vessels can injure or kill seals. The most effective way to reduce vessel disturbance is for vessels to stay away to keep seals and vessels apart. In the Greater Atlantic Region, we have issued “Watch for Seals on the Shoreline” guidelines to reduce the disturbance of gray seals.
Implementing Oil Spill Response Plans in the Event of a Spill
Gray seals are at risk of harm in the event of an oil spill. To minimize the effect of a potential spill on gray seals, NOAA developed the Marine Mammal Oil Spill Response Guidelines.
Overseeing Marine Mammal Health and Stranding Response
We work with volunteer networks in all coastal states to respond to marine mammal strandings. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health. When stranded animals are found dead, our scientists work to understand and investigate the cause of death. Although the cause often remains unknown, scientists can sometimes identify strandings due to disease, harmful algal blooms, vessel strikes, fishing gear entanglements, pollution exposure, and underwater noise. Some strandings can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Educating the Public
NOAA Fisheries aims to increase public awareness and support for gray seal conservation through education, outreach, and public participation. We share information with the public about the status of gray seals, as well as our research and efforts to promote their recovery.
All marine mammals, including gray seals, are protected in the United States under the MMPA.
NOAA Fisheries conducts various research activities on the biology, behavior, and ecology of gray seals. The results of this research are used to inform management decisions for this species.
Determining the size of gray seal populations helps resource managers determine the success of conservation measures. Our scientists collect population information and present the data in annual stock assessment reports.
Monitoring Population Abundance and Distribution
Scientists observe gray seals to record their numbers and distribution. By comparing numbers collected over multiple years, scientists can look for trends—i.e., whether the population is increasing, decreasing, or remaining stable during a given period.
We use photographs taken from the air to monitor gray seal populations in New England. We monitor the number of gray seals pups born in the following pupping colonies: Muskeget, Monomoy and Nomans Islands in Nantucket Sound, as well as Seal, Green, Matinicus Rock, and Wooden Ball Islands off mid-coast Maine. Our scientists also track gray seals to study their movements and habitat use.