A family very close to seals (Phocidae) is the sea lion family. They may look very similar to seals at first glance, but there are big differences. Do you know the difference? On this page, you will get to know the sea lion family a little better.

The sea lion family is also known as eared seals. They derive this name from their auricles. In the scientific world, we call this family Otariidae. Like seals , sea lions belong to the order Carnivora, or carnivorous mammals. Bears, lions, wolves and walruses are also members of this order. Sea lions are carnivores. They hunt fish, crustaceans and shellfish in shallow coastal waters.

Sea lions, seals and walruses are often placed in a special group of marine mammals. This group is called the pinnepeds (Pinnipedia). You might have guessed it: this group gets their name from the shape of the legs. In these animals, the legs are very short, but with very long toes and fingers. This makes them look like they have fins.

Sea lions are often confused with seals. Do you have any idea how you can actually distinguish a sea lion very easily? Their name (eared seals and Otariidae) kind of gives it away: the ears. You can see little auricles protruding from the side of their heads. Seals and walruses do not have these; they have holes as ears.

De lichaamsbouw van zeeleeuwen lijkt wel wat op dat van zeehonden. Ze hebben een lang lichaam met een grote borstkas. Ze zijn over het algemeen wat slanker gebouwd dan zeehonden, met een spitsere kop. De voorpoten van zeeleeuwen zijn een stuk langer dan die van zeehonden.

Sea lions can move a lot more smoothly over land than seals. This is because they can fold their rear flippers forward. By leaning on their front and rear flippers, they can simply walk on land. And when needed, for example to flee, they can even run quite fast!

You can usually clearly see the difference between males and females in adult sea lions. Males are a lot bigger, with a very large chest, thick neck and larger head. This distinct difference between males and females is called sexual dimorphism.

Did you know...

Sea lions are incredibly good swimmers. Just like other pinnipeds, for that matter. They just take a slightly different approach from seals and walruses. Seals and walruses use their hind flippers to gain speed and their front flippers to steer. Sea lions do the opposite.

Sea lions have very long front flippers. Instead of their rear flippers, they use these long front flippers to gain speed. They move their front flippers up and down, like wings. By doing this, they push themselves forward through the water. They then use their rear flippers to steer.

Because they swim this way, sea lions are a lot more agile than seals. But, they cannot swim as long and deep as seals.

Sea lions are social animals: they often live together in huge groups. These groups are also called colonies. During the mating season, an entire colony often lies together on the coast. Within a colony, there are smaller groups consisting of a male and his harem. These harems can sometimes consist of dozens of females!

Especially when hunting, sea lions are a lot more social than seals. Sea lions often hunt schools of fish in groups. By working together, they can easily catch fish from schools. This is much more difficult for seals, which hunt alone.

Did you know...

In the Pacific, sea lions are fairly widespread. They live mostly in tropical and subtropical seas (California and Galápagos, for example), but also in the more temperate and sub-Antarctic regions (such as South America and New Zealand).

Sea lions always mate and have their pups on land. Therefore, there are no species found in the Arctic. The only places in the Atlantic where sea lions live are the southern tip of the African continent, and along the South American coasts. So here in Europe, you cannot see sea lions in the wild.

The family of sea lions (Otariidae) consists of 14 species in total. These are often divided into 2 groups based on their appearance. The fur seals or sea bears (Arctocephalinae) are slightly smaller and get their name from the longer fur around the chest and neck. In these animals, you can see an extreme size difference between males and females (sexual dimorphism). This group consists of eight species. The sea lions (Otariinae) are a bit larger, have smoother fur and have a somewhat smaller difference between males and females. This group consists of 6 species.

Did you know...

However, this outdated division is still often used, as it is convenient to divide the sea lion family based on their external characteristics. Once a scientific consensus is reached, this article will be updated.

Northern fur seal (Callorhinus ursinus)
South American fur seal (Arctocephalus australis)
New Zealand fur seal (Arctocephalus forsteri)
Antarctic fur seal (Arctocephalus gazella)
Galápagos fur seal (Arctocephalus galapogoensis)
Juan Fernández fur seal (Arctocephalus philippi)
Cape fur seal (Arctocephalus pusillus)
Subantarctic fur seal (Arctocephalus tropicalis)

Steller sea lion (Eumetopias jubatus)
Australian seal ion (Neophoca cinerea)
South American sea lion (Otaria flavescens)
California seal ion (Zalophus californianus)
Galápagos sea lion (Zalophus wollebaeki)
New Zealand sea lion (Phocarctos hookeri)

A family close to seals (Phocidae) is the walrus family. In terms of behaviour and body shape, they are very similar to seals and sea lions. Yet many walruses have one very recognisable feature: their tusks. Read on to get to know walruses a little better.

The family of walruses is also known in science as the Odobenidae . Like seals, walruses belong to the order Carnivora, the carnivorous mammals. This order also includes animals such as wolves, bears and lions.

Walruses are one of the three members of the Pinnipedia (pinnipeds). This group of mammals is special because they spend much of their lives in the water. Their front and hind legs have turned into fins after millions of years of evolution, allowing them to move very well in water. The other two members of this group are sea lions (Otariidae) and seals (Phocidae).

This family is a bit special because it only has one relative! It might be a bit confusing, but the only species in the walrus family (i.e. the Odobenidae) is the walrus (Odobenus rosmarus). All other species have unfortunately been extinct for a long time.

Walruses, like other pinnipeds, have a large, rounded thorax. Their abdomen is relatively small, giving them a cone-shaped body. They have shorter front flippers than sea lions. Nevertheless, walruses can lean on these, allowing them to lift their head and thorax off the ground.

Walruses have a lot less fur than seals and sea lions. Adult males sometimes look as if they have no fur at all. To stay warm, walruses have a thick layer of blubber. It often looks like walruses have extremely many small rolls of fat, especially the adults.

The only species still alive today (Odobenus rosmarus) has very recognisable tusks protruding down from the upper jaw. Fossils of very old walrus species show that many of their extinct relatives also had tusks.

Walruses, like sea lions, can fold their rear flippers forward. This allows sea lions to lift their entire body off the ground to walk. Walruses cannot do that: they are too heavy for that.

Walruses move over land by dragging themselves forward with their front flippers. In the process, they push off with their rear flippers. The belly does not come off the ground in the process, so it slides over the ground. On land, they are somewhat more clumsy than sea lions.

The way walruses move in the water is very similar to how seals do. They use their rear flippers to gain speed, but do not hold them flat against each other. They paddle alternately with their rear flippers while moving the abdomen back and forth.

Walruses are social animals. On land, they lie down together in very close groups to rest. They also like to swim in groups in the water. Outside the mating season, males and females will usually live separately from each other. Walruses are pregnant longer and take care of their pups a lot longer than seals and sea lions.

During the mating season, different groups of males and females come together in a large group. The males then fight each other for a piece of territory. These fights can be fierce.

The only walrus species alive today is found around the Arctic. They need shallow water with a soft seabed to hunt well. Therefore, they usually do not go very far from the shore. Walruses often rest in groups on sandy or rocky shorelines, as well as on the ice.

Walruses also used to occur a lot further south. Archaeodobenus, a primordial walrus, lived around Japan about 6 million years ago. At the same time, species also lived around California, such as the Gomphotaria. It seems they all lived in the northern hemisphere, as did the only surviving species.

What is a seal? What do seals look like and do you know how they differ from sea lions? How many species of seals are there and where do they live? On this page you will learn more about the seal family.

The group of animals that we call true seals are all members of the family Phocidae .

Seals are mammals that live in the ocean, also known as marine mammals. Together with the family of sea lions and the family of walruses they are placed in a special clade of marine mammals. This clade consists of so called pinnepeds (Pinnipedia).

Pinnipeds got their name from the shape of their flippers. These animals have very short flippers, but with very long fingers and toes. This makes it look as if they have fins.

Seals belong to the order of mammals that mostly eat meat: CarnivoraThis order also includes animals such as bears, lions, wolves, sea lions and walruses .

Did you know...

Seals are carnivores, which means that they must eat other living animals to survive. They often eat fish, crustaceans and shellfish. Some species can eat very small animals such as krill. Others hunt for even bigger prey such as birds and other mammals.

You can partially recognize seals by their special physique. They have a long body with a broad chest and a small lower body. This gives them a streamlined, cone-shaped body. Their flippers are very short and wide and they have five digits which are webbed. This makes them perfectly suited for aquatic life.

Sea lions and walruses have similar physiques and adaptations, so what makes seals stand out? First of all, seals’ hind flippers cannot be folded underneath their body to walk on. Sea lions and walruses are able do this, which it easier for them to "walk" on land.

Seals have to hobble on their bellies to move on land. The way in which seals move is also referred to as caterpillar-like motion.

Another difference are their ears. Sea lions have small external ear flaps. Seals don't have such visible ears, they have ear holes on the side of the head.

Did you know...

Seals are strong swimmers. They have to be, as seals spend a lot of time in the water. In general seals can stay underwater for a longer period of time than sea lions and walruses. To hunt for food, some seal species must be able to dive very deep.

A seal has a special way of swimming. To speed up, seals swim with their hind flippers by holding them flat against each other and moving them quickly side to side. You could compare this to how fish swim. Fish also whip their tail to the side to move through the water. The front flippers are a lot smaller than the back flippers. They also don't use it to move forward, but to steer.  

Did you know...

Most seal species live a solitary lifestyle. This means that they prefer to do almost everything on their own. The only exception is during the mating season, because then the animals congregate in large numbers to birth pups and mate. When mating season is over, the seals moult together, after which they each go their separate ways.

You can see seals resting in groups on beaches and sandbars, but that does not mean that they like to be together. Because seals are less agile on land, they cannot run away from large predators. Therefore, when the seals are on land it is safer for them to be with other seals. Additionally, often times there is not enough space to lie far apart so they are “forced” to be closer than they would want to.

Seals can be found in every ocean of the world. They often live along the coasts or on the ice of the North or South Pole. There is even a species of seal that does not live in the sea, but in the freshwater Lake Baikal in Russia! Each species is adapted to live in certain areas and not one seal species can be found all over the world.

Did you know...

The true seal family (Phocidae) is often divided into two subfamilies: northern seals (Phocinae) and southern seals (Monachinae). The group of northern seals consists of ten species. The southern seal group is made up of eight species. Worldwide there are a total of eighteen different seal species.

Bearded seal (Erignathus barbatus)
Hooded seal (Cystophora cristata)
Harp seal (Pagophilus groenlandicus)
Ribbon seal (Histriophoca fasciata)
Baikal seal (Pusa sibirica)
Ringed seal (Pusa hispida)
Caspian seal (Pusa caspica)
Largha seal (Phoca largha)
Common seal (Phoca vitulina)
Grey seal (Halichoerus grypus)

Leopard seal (Hydrurga leptonyx)
Weddell seal (Leptonychotes weddellii)
Crabeater seal (Lobodon carcinophaga)
Ross seal (Ommatophoca rossii)
Northern elephant seal (Mirounga angustirostris)
Southern elephant seal (Mirounga leonina)
Hawaiian monk seal (Neomonachus schauinslandi) Mediterranean monk seal (Monachus monachus)

Seals belong to the order Carnivora. This is a special group of animals within the class Mammalia (mammals). Carnivora are mammals that are specialized in eating other animals, better known as carnivores.

Did you know...

Millions of years ago, dinosaurs were the dominant animals on Earth. During that time there were mammals, but their fossil records showed that they were the size of tiny shrews. They specialized in living nocturnal lives, a feature that mammals still have to this day.

The first mammals ate insects in order to survive. After the massive extinction of the dinosaurs there was room for mammals to expand and evolve. This resulted in various mammals with all kinds of specializations. This gave rise to the specialization of eating meat; the birth of the order Carnivora.

The oldest Carnivora fossils that have been found are from the Miacis congnitus. These predators somewhat resembled modern civets with their long, agile bodies and long tails. Miacis most likely lived in trees and ate small invertebrates, reptiles and birds. They lived during the late Paleocene and early Eocene epoch (62 – 34 million years ago). All modern Carnivora descend from these prehistoric animals, including seals.

Do you want to learn more about the evolution of the seal family? Check out our page on the evolutionary history of the Phocidae.

All the Carnivora are mammals (Mammalia). This means that they nourish their offspring with milk.

All Carnivora are 'viviparous’. This means that they develop their offspring in the placenta inside the uterus of their mother and give birth to "living” young.

Carnivora have a relatively large skull with a large cranium. They have large brains and are considered to be intelligent animals. In general Carnivora have somewhat rounder heads than other mammals. These rounder heads ensure that their eyes are well positioned for hunting other animals.

The shape and position of their eyes are striking. Carnivora have relatively large eyes that are close together. Because both their eyes face forward, Carnivora such as seals have a very good depth perception. This is extremely important for carnivores. After all, in order to hunt other animals they must be able to see exactly how far away their prey is.

But the easiest way to recognize Carnivora is by their teeth. Because Carnivora eat meat, their teeth have been adapted to killing and eating animals. They have large, pointed canine teeth and sharp, serrated molars. This helps carnivores to cut muscles and tendons and even crack bones.

Did you know...

Thes two words can be confusing, because they seem very similar. They do not have the same definition.

The Carnivora are an order of mammals that are adapted to eating meat. To survive, they must kill animals or find carcasses. When talking about Carnivora we are talking about the classification of carnivores in relation to other mammals. Examples are wolves, lions and seals.

But these mammals are not the only animals that eat meat. If an animal's diet consists mainly of meat, we are talking about a carnivore diet. Birds of prey, crocodiles, Tyrannosaurus rex and seals are therefore all carnivores.

To eat and digest high-fiber plants (such as grass) you need an extremely long and complex digestive system. This is because plants are very difficult to digest and that take a lot of time. They also have very few nutrients, therefore herbivores are almost constantly eating.

Meat, on the other hand, is easier to digest. Carnivora therefore have very short, simple digestive systems. Meat is also very rich in energy and protein, so they can spend less time eating compared to herbivores.

But depending on energy alone is not enough to survive. As you may know, animals also need vitamins, fats and minerals. Therefore, Carnivora not only eat the meat from their prey, but also their organs, fat, skin and sometimes even their bones. It contains all the nutrients an animal could wish for. Seals, for example, swallow many of their prey whole. Skeleton and everything else.

Did you know...

Not always. There are species that eat almost exclusively meat, but there are also Carnivora with a mixed diet. Yet we still call them carnivores, because their bodies are mainly specialized in eating and digesting meat.

If the diet of a Carnivora consists of at least 70 percent meat, we call them hypercarnivores. Ze kunnen ander voedsel slecht of niet verteren. Zeehonden en de andere Pinnipedia are hypercarnivores. They only eat meat, so no plant materials.

There are also Carnivora with a mixed diet. If they consume meat for less than 30 percent of their diet, we call them hypocarnivores. They often eat mushrooms and fruit in addition to meat. These contain little fiber and a lot of sugars and proteins, so they are quite easy to digest for Carnivora. Brown bears (Ursus arctos) are known hypocarnivores. For their hibernation they have to build up a lot of reserves. That is the reason why they eat everything they come across.

In between the hyper- and hypocarnivores you have so-called mesocarnivores. Their diet consists of 50-70 percent meat. Many canids are mesocarnivores. They mainly eat meat, but they can also digest certain plants as long as they don't contain too much fiber.

Did you know...

Within the order Carnivora there are 16 families and 296 species. The families are divided into two suborders : the Caniformia and the Feliformia.

The suborder Caniformia consists of nine families:

• Canidae (canids)
• Ailuridae (red panda)
• Mephitidae (skunks and stink badgers)
• Procyonidae (e.g. raccoons)
• Mustelidae (e.g. weasels)
• Ursidae (bears)
• Odobenidae (walruses)
• Otariidae (sea lions)
• Phocidae (seals)

The suborder Feliformia consists of seven families:

• Felidae (felines)
• Eupleridae (Madagascarian carnivorians)
• Herpestidae (mongooses)
• Hyaenidae (hyenas)
• Nandiniidae (African palm civets)
• Prionodontidae (Asiatic linsangs)
• Viverridae (civets and genets)

Did you know...

As the name suggests, seals live in salt water. Nevertheless, it sometimes happens that we receive a report of a seal in an area with fresh water. Such a report often comes in with the question: "Isn't that a bad thing?"

Luckily, that is not the case. A seal mainly needs fish to survive and they are also in fresh water. There are reports of seals in the Utrecht canal, the Schildmeer and in the major rivers. Seals are smart. They usually find their way back. 

Seals don't necessarily need to be in salt water to survive. Unlike other marine animals, they are not very sensitive to the salinity of water. It is true that after a while their eyes can get irritated. Apart from that, seals can survive in fresh water for a while. As long as there's plenty of fish to hunt.

The two most recent cases reported to us are seals Hulcky and Thor. We took Hulcky from the Veluwemeer when it turned out that she was suffering from a lungworm infection. She was taken in at the Sealcentre and eventually released back into the sea.

Seal Thor was just seen in the fresh water of De Onlanden after we had caught and released him. Thanks to its tag and its spots on fur, we were able to recognize that it was this specific seal. After a while he found his way back on his own.

Since March 2012 we have had more reports:

• March 2012: common seal near Goudswaard, South Holland.
• December 2012: common seal in the Biesbosch.
• December 2012: common seal in the Schildmeer, Groningen. The animal seemed to swim back and forth between the Schildmeer and Farmsum.
• January 2013: common seal in the Meuse near Dreumel.
• April 2013: common seal in river Hunze in Drenthe, moved on by itself.
• December 2013: common seal in the Schildmeer, Groningen. Unknown if it was the same seal. The animal was seen with fish in its mouth.
• August 2015: ringed seal in Utrecht canals, collected at seal sanctuary A Seal in Stellendam.
• October 2015: common seal in Biesbosch.
• March 2016: common seal in the Maasplassen near the Weerd in Roermond.
• November 2016: common seal “Hulcky” spotted in Veluwemeer.
• August 2021: common seal Thor spotted first in Peizerdiep, later in De Onlanden.

The seal species that occur in the Netherlands all live in salt water. But there are seal species in the world that actually live in fresh water. There are five in total. These populations probably became separated from the sea long ago.

It concerns the following five species:

Lake Iliamna, Alaska Phoca vitulina mellonaea freshwater subspecies of the common seal.
Lake Baikal, Siberiia Pusa sibirica, Baikal seal , a separate species. Also the smallest seal species.
Lake Ladoga, Russia Pusa hispida ladogensis, freshwater subspecies of the ringed seal.
Lake Saimaa, Finland Pusa hispida saimensis, freshwater subspecies of the ringed seal.
Lac des loups marins, Quebec Phoca vitulina mellonae, a freshwater subspecies of the common seal.

Bron: Van Lanen, 2012

It is believed that more seals visited the Dutch inland waterways in the past, but that has decreased in the last century.

The construction of flood defenses in all major rivers in the Netherlands has probably contributed to this. Because of all the locks, dikes and scuppers, it is quite difficult for a seal to find an easy way to inland. Sometimes seals find a way, but they get lost along the way and can't find their way back. If those animals do not receive enough food, then action must be taken to help them return to the sea. In other cases, seals seem to know very well how to move between sea and lake.

The seal that has already been seen a number of times in the Schildmeer, for example. It was first seen at Farmsum, then at Schildmeer. To get to that lake, the seal first had to swim through a channel to the south, and then swim into a small drainage channel. When the animal was later spotted again at Farmsum, it seemed that the animal knew what it was doing. A year later another seal was seen in the Schildmeer.

It has been said by several people that the seals may be able to learn how locks work.

Due to industry, agriculture and waste water from households, the water quality has deteriorated rapidly in the last century. Due to the deteriorating quality of the freshwater ecosystem, many freshwater bodies became uninhabitable for certain fish species. As a result, diversity in many freshwater bodies also declined sharply. As mentioned before, seals need a lot of fish to survive. If that fish is not there, a seal will not easily choose to hang out in such an area.

In the past few years, a lot of work has been done to improve the water quality. And that will continue. Various projects are also being developed to increase the species richness in Dutch waters. For example, by leaving the sea locks ajar and creating fish passages in dikes, it is hoped that migrating fish species will return to the Dutch interior. With this return, they hope that the ecosystem will improve.

Perhaps with this improvement we will encounter more seals in Lake Veluwe in a few years?