Diet & Eating Habits

Adult harbor seals eat 5-6% of their body weight per day, about 4.5-8.2 kg (10-18 lb.).

Harbor seals don’t chew their food. They swallow their food whole or tear it into chunks. With their back molars, they crush shells and crustaceans.

Foraging

In dark or low light conditions, a harbor seal uses its sensitive vibrissae to find food.

Harbor seals generally obtain the water they need from their food. If food intake is decreased, the metabolic breakdown of fat produces water. The metabolism of 0.45 kg (1 lb.) of fat produces 0.64 kg (1.4 lb.) of water.

What Do Seals Eat?

Seals live in a wide variety of ocean environments ranging from frigid polar waters to tropical seas. Seals are perfectly adapted to their marine lives, with a physiology that allows them to forage for food at great depths.

Although seals live primarily in the water, they are mammals. And, like other mammals, are warm-blooded and suckle their young. While they have many similarities to whales and dolphins, seals must give birth to their pups on land and shed their skin on land yearly.

Types

There are 35 species of seals, all of whom belong to the Order Pinnipedia. These species can be divided into three general families: fur seals and sea lions; walruses; and ‘true’ seals. The differences between the seals rests primarily on whether they have external ears, how well they can maneuver on land, and whether they have a thick or thin coat.

Seals have a highly specialized physiology that allows them to dive to great depths in search of food, to sustain these dives for extended periods of time, and to resurface without experiencing the “bends.” When a seal begins a dive, its heart rate slows to 1/10th of its normal rate, the arteries constrict, and blood flow is greatly decreased to all organs except for the sense organs and the nervous system. All seals are highly tolerant to the pain and fatigue associated with the lactic acid that accumulates during extended dives that can last for up to an hour and at depths of more than 655 feet.

Features

All species of seal generally eat octopus, squid, shellfish, cod, herring, flounder, sculpin, salmon, mackerel, sandeel, shrimp, whelk, and other crustaceans such as krill. However, some seals specialize in only certain types of seafood; for instance, Southern Elephant seals eat mainly squid while walruses eat mainly mollusks.

While seals are in constant danger from their natural enemies, sharks, killer whales, and, in the Arctic, polar bears, the greatest threat to them are humans. Fisherman often kill seals that become entangled in their nets, and pollution–whether in the form of liquid pollutants in the water or ropes, packaging straps, or discarded fishing nets–can either poison or suffocate seals.

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Michelle Kerns writes for a variety of print and online publications and specializes in literature and science topics. She has served as a book columnist since 2008 and is a member of the National Book Critics Circle. Kerns studied English literature and neurology at UC Davis.

What Do Seals Eat?

Just a look at a seal’s skull gives you a hint as to what makes up its diet. If you didn’t know better, you’d think it was the skull of a wolf, with its fangs and carnassial teeth meant for grabbing and shearing meat. Indeed, seals are carnivores. They’re not only carnivores but are quite skilled and persistent hunters. The difference is that wolves hunt on the land while seals hunt in the ocean. To help them do this, nature has not only equipped them with fangs but flippers, torpedo-shaped bodies, and layers of blubber if they make their living in the colder seas.

Seals are members of the Pinnipedia order, which is divided into three families and about 34 species. Two include the true seals, the fur seals, and sea lions. The 10 foot long, one-ton walrus with its famous tusks make up a family of its own. Read on to learn what makes up the seal’s diet and how it gets its food.

What Foods Do Seals Eat?

Seals eat shrimp, octopus, fish, and krill.

As carnivores, seals eat aquatic animals, mostly fish. However, some seals have a surprisingly varied diet. The endangered New Zealand sea lion, for example, eats not only fish but squid and octopus and crustaceans such as shrimp. It will even eat other seals and has been known to catch and eat insects and seabirds.

The walrus appears to be an invertebrate specialist. It takes mollusks, marine worms, sea cucumbers, sea squirts, and other tunicates and soft coral. It hunts along the bottom of the sea and can find prey through its sensitive whiskers. It uses its flippers and blows jets of water into the seabed to clear it. When a walrus finds prey, it grips it with its lips and sucks the meat out of the shell. The walrus rarely eats seabirds and bits of other seals and might scavenge if it finds a dead whale.

The Antarctic fur seal’s diet is mostly krill, but they’ve been known to eat penguins. Harbor seals have been known to eat ducks, and gray seals have been known to eat harbor porpoises. These porpoises can grow to over six feet long and weigh 168 pounds, but grown gray seal bulls are larger. They can be over seven feet long and weigh 680 pounds.

How Do Seals Hunt Prey?

Fish are the main part of a seals diet.

Some seals, such as the California sea lion, hunt cooperatively with dolphins who can corral great schools of fish. Many seals range far and wide and dive deeply to hunt for prey. The Weddell seal can dive as deep as 1968.5 feet and stay submerged for an hour looking for prawns and other bottom feeders. Harbor seals can swim as far as 31 miles from their resting areas and stay out there for days looking for food.

Northern elephant seals swim as much as 13,000 miles through the ocean in search of food and don’t return to land until it’s time to reproduce and molt. Not only this, but they can dive to over 5000 feet and hold their breath for close to two hours. They also have several physical adaptations that allow them to conserve energy and oxygen while they’re diving.

The leopard seal has a good repertoire of hunting strategies. It stalks penguins along the edges of the ice where the bird lives. When the penguin comes into the water, the seal grabs its feet and shakes and bashes it to death. It then rips the animal into manageable pieces. Like the walrus, the leopard seal uses suction to eat small fish. When it hunts for krill, the leopard seal uses filter feeding. Its back teeth come together in a way that lets it strain krill from the ocean. This is also true of the crabeater seal. The crabeater seal, by the way, doesn’t eat crabs so much but specializes in krill.

The ribbon seal of the North Pacific Ocean have weaker fangs than some other seals, and they hunt their prey by piercing them with their teeth and swallowing them whole as opposed to tearing them to pieces.

Monk seals forage on the bottom of the sea and have been seen flipping over rocks to look for prey. Still, as fast swimmers they can pursue prey in open water.

Some seals have different strategies depending on the time of day. The Baikal seal uses its eyes to search for fish during the day, while at night it uses touch to find crustaceans.

Facts About Seals & Sea Lions

Seals and sea lions are semiaquatic mammals that are in a group called pinnipeds, meaning “fin-footed.” Walruses are also members of this group. While related, all three are in different taxonomic families.

“True” seals, also called earless seals, are members of the Phocidae family, according to the Integrated Taxonomic Information System (ITIS). Sea lions are members of the Otariidae family (eared seals), along with several species of fur seals. Walruses are in the Odobenidae family.

As their names imply, one difference between the two types of seals is their ears. Eared seals have external ear flaps, while true seals do not. Another difference is that the rear flippers of true seals point backward, and these seals move on land with an up-and-down undulating motion. Fur seals and sea lions can rotate their hind feet and use them to walk along with some speed. Also, fur seals are so-named because they have thick fur that can trap air and help keep them warm. True seals have thin fur and use blubber for insulation.

Seal sizes

There are 18 species of true seals, according to Seals World. The largest is the southern elephant seal. Males are massive, weighing up to 8,500 lbs. (3,855.5 kilograms). Females are much smaller, but still weigh more than a car at 2,000 lbs. (907.18 kg). Males measure about 20 feet long (6 meters), while females are about half as long.

The Gulf of the Farallones National Marine Sanctuary is home to one fifth of California’s harbor seals. These marine mammals rely on safe havens within the Sanctuary to haul-out, rest, and breed. (Image credit: NOAA, Photo Library/Jan Roletto)

The smallest is the ringed seal, with an average length of 5 feet (1.5 m) and a weight of 110 to 150 lbs. (50 to 70 kg). Unlike other seals, males and females are about the same size. The ringed seal is the most common seal in the Arctic, according to the National Oceanic and Atmospheric Administration (NOAA).

There are 16 species of eared seals; seven of them are sea lion species. One of the most recognized species, according to the NOAA, is the California sea lion, which is often featured doing tricks at zoos and aquariums. In the wild, these animals live along the West Coast of North America. They are often seen sunning themselves on beaches, docks and jetties. Males average about 700 lbs. (315 kg) and can reach above 1,000 lbs. (455 kg). Females average 240 lbs. (110 kg). [Gallery: Seals of the World]

Habitat

True seals typically live in the cold ocean waters of the Arctic or off the coasts of Antarctica. Some seals make caves in the snow to live in. Others never leave the ice pack and poke breathing holes in the ice, according to the National Snow and Ice Data Center. Harp, ringed, hooded, spotted, bearded and ribbon seals live in the Arctic. Crabeater, Weddell, leopard and Ross seals live in the Antarctic.

Fur seals and sea lions live in the Northern Pacific between Asia and North America and off the coasts of South America, Antarctica, southwestern Africa and southern Australia. They can spend about two years in the open ocean before returning to their breeding grounds, according to the NOAA.

Seals generally prey on fish, but they will also eat eel, squid, octopus and lobster. Leopard seals will eat penguins and smaller seals, according to Seals World. The gray seal can eat 10 pounds (4.53 kilograms) of food in one day. They sometimes skip eating for a few days, and often stop eating completely during mating season and will live off energy from their stored-up blubber for weeks.

The seal pup and Ursula, the mother. The baby is the first born at the New England Aquarium in Boston, which is trying to breed the vulnerable animals. (Image credit: New England Aquarium)

Baby seals

When mating season comes, male seals will issue deep, throaty calls to attract the attention of females. A male seal will also call out to let other males know that his females are spoken for. Males are very territorial when it comes to mating. They will fight for the right to mate, hitting and biting each other. The winner gets the chance to mate with up to 50 females in their area.

Mothers carry their young for a gestation period of around 10 months. When they feel the time is right, some seals will dig nests in the sand on which to have their young. Seals and sea lions have just one pup a year. Others, like the harp seal, will have their babies directly on icebergs. Baby seals, called pups, will stay on land until their waterproof fur grows in. This can take around a month.

Females will mate and become pregnant again as soon as her pups are weaned. Males are not able to mate until they are around 8 years old, because it takes that long for them to grow big enough and strong enough to win a mating fight.

Classification/taxonomy

All pinnipeds — phocids (true seals), otariids (eared seals) and odobenids (walruses) — are in different families in the suborder Caniformia (doglike carnivores) and are related to dogs, coyotes, foxes, wolves, skunks, otters and bears.

The taxonomy of seals, according to ITIS, is:

Eared seals (fur seals and sea lions)

• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Suborder: Caniformia
• Family: Otariidae

Genera and species:

• Arctocephalus (southern fur seals — eight species)
• Callorhinus ursinus (northern fur seal)
• Eumetopias jubatus (northern sea lion or Stellar sea lion)
• Neophoca cinerea (Australian sea lion)
• Otaria flavescens (South American sea lion)
• Phocarctos hookeri (New Zealand sea lion)
• Zalophus (California sea lions — three species)

True seals

• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Suborder: Caniformia
• Family: Phocidae

A killer whale identifies a Weddell seal resting on an ice floe off the western Antarctic Peninsula. The whale will notify other killer whales in the area so they can coordinate a wave to wash the seal off the floe. (Image credit: Robert Pitman/NOAA)

Genera and species:

• Cystophora cristata (hooded seal)
• Erignathus barbatus (bearded seal)
• Halichoerus grypus (gray seal)
• Histriophoca fasciata (ribbon seal)
• Hydrurga leptonyx (leopard seal)
• Leptonychotes weddellii (Weddell seal)
• Lobodon carcinophaga (crabeater seal)
• Mirounga (elephant seals — two species)
• Monachus (monk seals — three species)
• Ommatophoca rossii (Ross seal)
• Pagophilus groenlandicus (harp seal)
• Phoca (hair seals, harbor seals)
• Pusa (Caspian seal, ringed seal, Baikal seal)

Conservation status

All pinnipeds — seals, sea lions and walruses — are protected in U.S. waters under the Marine Mammal Protection Act, according to NOAA. Most seals are not considered endangered, according to the Red List of the International Union for Conservation of Nature (IUCN). There are a few exceptions, though. The Galápagos fur seal and the monk seal are both endangered. Some local populations, such as gray seals in the Baltic Sea, are endangered. The northern fur seal and hooded seal are vulnerable. The Caribbean monk seal was declared extinct in 2008.

The crabeater seal has the largest population of any species of seal in the world. It is estimated there are 2 million to 75 million individual seals, according to the IUCN.

Elephant seals have what is called “smoker’s blood” because they have the same amount of carbon monoxide in their blood as a person who smokes 40 or more cigarettes each day, according to researchers. Scientists think this high level of gas in their blood may protect them when they dive to deep levels in the ocean.

Harp seals can stay underwater for up to 15 minutes. Weddell seals are even more impressive. The can stay underwater for up to 80 minutes. They only pop up for air when they find holes in the ice layers above the ocean.

Nina Sen contributed to this article.

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Alina Bradford is a contributing writer for Live Science. Over the past 16 years, Alina has covered everything from Ebola to androids while writing health, science and tech articles for major publications. She has multiple health, safety and lifesaving certifications from Oklahoma State University. Alina’s goal in life is to try as many experiences as possible. To date, she has been a volunteer firefighter, a dispatcher, substitute teacher, artist, janitor, children’s book author, pizza maker, event coordinator and much more.

How to Feed Seals

Seals love to hunt for their food. In aquariums, they are usually fed on fish by offering these foods in the water or by hand. They can however be very dangerous which means you probably should avoid feeding a wild seal.

What Do Seals Eat In The Wild?

In the wild, seals eat foods that are available in their natural habitats such as fish, penguins, crustaceans, krill, squid, and other food. Seals usually do not migrate, but may choose to do so if there is no food in their habitat.

What Do Seals Eat In Captivity?

In captivity, seals are fed on small fish, squid, and krill. Seals enjoy eating all sorts of seafoods in captivity and they can also be taught to perform in front of audiences and are usually awarded fish.

What do Baby Seals Eat?

Baby seals are called pups. Pups usually stay on land for about a month until their waterproof fur grows in after which they will start to swim. Seals are mammals and feed by drinking from their mothers. From one month on, seal mothers will bring their pups fish so they can start to feed on solid foods. When pups are first weaned from their mothers, they will drastically lose a lot of weight. They can lose up to 1 third of their weight while they are learning to hunt. When the pup is strong enough, it will join its mother and will learn to hunt for its own food.

How Much Do Seals Eat?

As a rule of thumb, seals eat 4 – 6 percent of their body weight every day. An average grey male seal weighs about 400 kg and needs about 15 – 23 kg of food every day. An average harbor seal weighs 136 kg and needs only 5 – 9 kg of food per day.

The biggest seal, the elephant seal, weighs about 2040 kg and needs to feed 81 – 123 kg food every day.

How Often Do Seals Eat?

In some months, seals need to eat as often as they can to store lots of blubbers. Female pups do however fast while they are still nursing their pups.

Seals also eat much less in wintertime because food can be very scarce in these months. During winter, seals will use their stored blubber to carry them through the winter.

Do Seals Bite Humans?

Seals can be very dangerous. They can lash out and bite humans if they feel threatened and some are even known to swim up to people on docs and might bite them. They have microorganisms in their skin and on their teeth that can enter your body when they bite you. These microorganisms can cause infections which is why seals can be very dangerous.

Their razor-sharp teeth are also perfectly capable of slashing through your skin within milliseconds.

Do Seals Eat Penguins?

Yes, seals do hunt and eat penguins. They can catch penguins on the islands or in the water. Fur seals are especially likely to catch and eat penguins.

Do Seals Drink Water?

Seals can drink seawater but they are not too likely to do so. They usually get enough moisture from the food they consume and do not need to drink water. If it is particularly hot, the seal will however drink water while swimming and they usually consume lots of water when they are swallowing their prey whole underwater.

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