Are Seals Mammals?

Written by AZ Animals Staff
Published: September 24, 2021
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Seals are mammals! They possess all the things that make an animal a mammal. They are warm-blooded, they are vertebrates, they have fur, and most of all, the mothers feed their babies with milk expressed through mammary glands. Indeed, seal milk is some of the richest milk there is. The milk of the hooded seal, for example, is so full of fat that the mother only needs to nurse her baby for two weeks, tops, before it’s independent.

Seals, also called pinnipeds, aren’t just mammals but belong to a special group called marine mammals. These mammals live most of their lives in or near water, especially the ocean. Pinnipeds spend most of their time in the water, hunting for something to eat, but they have to come out on land to give birth, mate, and molt their fur. This is one of the things that separates them from whales, dolphins, and porpoises, who are completely aquatic and are at risk of death if they are beached.

There are basically three types of pinniped. They are walruses, true seals, which don’t have external ears and need to drag themselves over land or ice, and sea lions, which have external ears and can manage to shuffle around on their flippers. Walruses, by the way, don’t have fur all over their bodies, but they have so many sensitive whiskers that they’ve inspired a style of human mustache. The closest living relatives to seals are bears, and seals separated from them about 60 million years ago.

Are Seals Mammals
A large grey harp seal lays on an ice pan with its face and body covered in snow. Seals, also called pinnipeds, aren’t just mammals but belong to a special group called marine mammals.

Dolores M. Harvey/Shutterstock.com

Why Would People Think Seals Are Not Mammals?

It is possible that people think pinnipeds are a type of fish, as some people think that whales and dolphins are types of fish. This is because they have fins and flippers instead of legs and are beautifully adapted for life in the water. But seals aren’t fish, but mammals.

Are seals endangered?

One out of five pinniped species is endangered due to reckless hunting, climate change, and pollution. Some pinnipeds are tangled up in nets meant to catch fish or other marine life. Global warming, for example, melts sea ice and makes it harder for them to find a place to haul out. Warming water doesn’t hold oxygen as well as cold water, and this reduces the abundance of the seal’s prey. Pollution is bad for marine life in general and even the noise made by sea vessels can be damaging. Here are some pinnipeds that are listed as endangered.

  • Mediterranean monk seals. There are less than 700 of these animals found in a handful of populations around the Mediterranean Sea. Because of this, it is one of the rarest pinnipeds in the world.
  • Ungava seal. This is a rare freshwater seal found in the north of Quebec. Scientists believe there are less than 100 of these animals left.
  • Saimaa ringed seal. This animal is another freshwater seal and is only found in Lake Saimaa in Finland. An estimated 400 individuals are left.
  • Hawaiian monk seal. This animal is one of two mammals that are endemic to Hawaii. The other is the Hawaiian hoary bat.
  • New Zealand sea lion. Also called the whakahao, this large pinniped is one of the rarest sea lions. It is the only species in the Phocarctos genus.
  • Australian sea lion. This sea lion, which is also the only species in its genus, is known for its strange breeding cycle.
  • Galapagos fur seal. This little seal is the smallest of the fur seals. It is only found in the Galapagos Islands.
  • Galapagos sea lion. This sea lion is found both on the Galapagos Islands and less frequently on Isla de la Plata. It is the smallest sea lion.
  • Walrus. This charismatic pinniped is famous for its tusks and its huge size. A big male can weigh over two tons. Its conservation status is vulnerable.
Are Seals Mammals
An endangered Hawaiian monk seal on a beach in Kauai, Hawaii. This seal is one of two mammals that are endemic to Hawaii.

Lorraine Logan/Shutterstock.com

Next Up: Discover the Largest Lobster Ever Caught!

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AZ Animals is a growing team of animals experts, researchers, farmers, conservationists, writers, editors, and -- of course -- pet owners who have come together to help you better understand the animal kingdom and how we interact.

FAQs (Frequently Asked Questions) 

What is a seal good for?

Seals have been hunted since antiquity. They were and in some cases still are hunted for their fur which is especially true of their pups. They’re also hunted for their meat and their blubber. More and more, pinnipeds are coming under the protection of laws that prohibit them from being recklessly hunted or hunted at all.

How many species of seals are there?

According to the IUCN, there are 36 species of pinnipeds. Some of these species have subspecies.

Where are seals found?

Seals are found mostly in the polar regions, though there are a few, such as monk seals, that are found in warmer waters such as the Mediterranean. Yet even if the waters are warm they cool down thanks to seasonal ocean currents. This allows them to become more nutrient-rich. The great majority of pinnipeds are found in saltwater, and only a few are found in freshwater. These include the Ungava, the Saimaa ringed, and the Baikal and Caspian seals.

Are they omnivores, herbivores or carnivores?

Pinnipeds are carnivores, as they eat only animals such as krill, squid, fish, penguins, and smaller seals, including the pups of other species.

Are seals dangerous?

They are not really dangerous to humans, but some are more aggressive than others, especially during the breeding season or if they are hungry. At least one human has been killed by a leopard seal. Scientists believe that the animal mistook the human, who was wearing snorkeling gear, for a type of seal that was the leopard seal’s usual prey. A look at the dentition of many pinnipeds reveals the fangs and carnassial teeth of carnivores, and even if an animal doesn’t mean to outright kill a human they can deliver a serious bite. Also, seals are surprisingly large animals. Pinnipeds such as the elephant seal and the walrus are just too huge to tangle with.

Do seals migrate?

Some species of pinniped do migrate. Indeed, the northern elephant seal’s migration is the longest of any mammal. Males swim 13,000 miles, and females swim 11,200 miles every year to find food then haul out to breed, molt and give birth. It was thought that hooded and harp seals didn’t migrate, but they might migrate down from their birthing grounds in Greenland and northeastern Canada to New England.

Why do seals molt?

Pinnipeds need to molt from time to time because their fur doesn’t keep them warm but just protects them from injury and getting burnt by the sun’s ultraviolet light. Also, they need to molt mostly on land because they need to send their blood close to the surface of their skin to encourage the growth of new fur. They couldn’t do this in the cold waters where most seals live because the blood would be shunted to their internal organs. With their fur and even their skin sloughing away they would become hypothermic very quickly. A seal that still visits the water during its molt takes a much longer time to get a new coat of fur.

Many pinnipeds molt right after they become pregnant, even though elevated pregnancy hormones can interfere with the molt. The animal gets around this through a phenomenon called embryonic diapause. While she’s molting, the embryo simply doesn’t develop and the hormones are kept in check.

There are animals that don’t just lose and regrow their fur but lose and regrow their top layer of skin. Elephant seals do this, and they not only have to stay on land for some weeks, but they can’t eat during this time. This is called a catastrophic molt.

How long do seals live?

The lifespan of a seal depends a lot on the species, but as mammals, seals can live a long time. The gray seal can live for over 30 years, the Galapagos sea lion can live between 15 and 24 years, the walrus can live between 30 to 40 years, and though a male elephant seal can grow to be nearly twice as massive as a walrus, it only lives between 11 and 13 years. Pups of all species are the most vulnerable to predation and even getting trampled to death by males of their own species as the bulls fight rival males or try to mate with the pup’s mother.

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