Walrus

Quick Take

• Walrus tusks were long assumed to be feeding tools, though their real purpose turns out to be far stranger and more versatile than scientists first believed. Tusk roles explained →
• Walruses can hunt prey in near-total darkness at crushing depths, and the body part they rely on to do it is not what you would expect. How walruses find prey →
• Despite having few natural predators, walrus populations have been collapsing for centuries, though the biggest threat is not the one most people name. Threats to walrus survival →
• A walrus pup is born already weighing as much as a full-grown adult human, and yet its development timeline holds an even more surprising milestone. Pup growth and milestones →

One of the most sociable marine mammals in the world is the lovable walrus. Though these creatures bellow and snort in comical fashion, flash their expressive whiskers, and flaunt their gorgeous ivory tusks in displays of dominance, they can be quite charming. However, they are under threat as the climate of our planet changes, melting the icy landscape that walruses thrive in.

Classification

The Walrus is a large marine animal that is found inhabiting the cold and icy waters of the Arctic Circle, whose exact relationship to Fur Seals and True Seals remains debated among scientists. Walruses are the second-largest ocean-dwelling mammals that come ashore to breed after Elephant Seals.

The Walrus is considered to be an increasingly vulnerable animal species, although gathering data on these elusive creatures can be difficult, so it is hard to determine exactly the current status of Walrus populations in the wild.

The scientific name of the walrus is Odobenus rosmarus, and they are classified in the family Odobenidae.

There are two subspecies of walrus:

• Atlantic Walrus (Odobenus rosmarus rosmarus): These walruses are found in icy northern Atlantic waters of Greenland, Canada, Norway, and Russia. They have large ivory tusks, which were hunted for in the 17th-19th centuries, causing them to become extinct in Newfoundland, Nova Scotia, and St. Lawrence. Males weigh between 2,646 and 3,307 lbs (1,200–1,500 kg) while females weigh up to around 1,323–1,543 lbs (600–700 kg). The population is 25,000.
• Pacific Walrus (Odobenus rosmarus divergens): The Pacific walrus inhabits the Northern Pacific Ocean between Russia and Alaska from the Bering Sea to the Chukchi Sea and also the Laptev Sea. Their tusks are smaller than the Atlantic species, but they are overall larger animals with males weighing up to 4,400 lbs (2,000 kg) while females can weigh more than 1 ton (907 kg). These species are also more migratory during seasonal shifts. Their population is 200,000.

Evolution

The most widely accepted theory about the origins of the walrus is that it shares a caniform (dog-like carnivoran) ancestor with true seals and ear seals that is most closely related to the modern bear. The first walruses were smaller than their modern counterparts, but reached larger sizes before evolving into true walruses and double-tusked walruses. As they evolved, they had tooth simplification, developed tusks, and acquired a combination of terrestrial and aquatic locomotion. They also developed a squirt and suction feeding mechanism.

These developments occurred over a time range of approximately 16.8 to 22.1 million years ago.

Anatomy and Appearance

Walruses have large and elongated bodies that are wider at the head and neck and taper towards their tail, which is embedded in a web of skin. Their tough and wrinkled skin is covered by a layer of sparse, coarse hairs and is generally grey or brown. However, whilst sunbathing out of the water, the skin of the Walrus (which can be up to 10cm thick around the neck and shoulders of males) develops a pink-red coloration.

Walruses have two pairs of flippers that are used to help to propel these large animals with great agility through the water, with their bodies powered by their back flippers while the front flippers are used to steer them in the right direction. On land, they move about awkwardly on all fours, curling their back flippers underneath them at right angles to give them more support. The skin on the bottom of their flippers is rough and knobbly, which helps to prevent these enormous animals from slipping on the ice.

Walruses have long tusks (extra-long upper canine teeth) that are used for both fighting and digging into the ice when they are pulling their heavy bodies out of the water.

Distribution and Habitat

Walruses are found throughout the northern Atlantic and Pacific Oceans, where they inhabit ice floes and rocky coastlines, along with spending a great deal of time in the freezing cold water. During the winter months when the ice is at its thickest, Walruses tend to prefer areas of thinner ice that they can easily break through to the surface from the water underneath. In the warmer summer months when the ice recedes, Walruses can be found more commonly on remote areas of rocky coastline.

Despite being well suited to the freezing conditions in the far north, Walruses have on occasion been known to venture further south in areas of Central Canada, around the United Kingdom, and even as far as the waters close to the Spanish coast. They do, however, spend most of their time in and around the Arctic Circle, where they are becoming increasingly under threat from global warming, which is rapidly depleting the ice that these animals rely on.

Behavior and Lifestyle

Walruses are incredibly sociable animals that live in large herds on the ice floes that can contain up to thousands of individuals and consist mainly of females (cows) with their young, along with some dominant males (bulls). When they retreat into the water to feed, these enormous herds break up into smaller bands numbering as few as ten individuals so there is less competition for food.

Male Walruses are almost double the weight of their female counterparts and have much longer tusks, which can grow up to a meter in length and are used primarily for fighting with competitors for the most favored breeding sites and the females that reside there. They are known to make a variety of vocal sounds, including loud bellows during the mating season that are easily and loudly produced thanks to the two pouches of air in their necks.

Reproduction and Life Cycles

Walruses most commonly breed in the middle of winter between January and March. After a gestation period that lasts for around 15 months, a single pup is born on the ice measuring up to 3.94 feet (1.2 meters) long and weighing up to 165.3 lbs (75 kg). Walrus pups have short and soft hair covering their bodies, pale grey flippers, and a thick, white mustache with no visible teeth.

They suckle only on their mother’s milk for their first six months, when they begin to eat more solid foods. After their first year, Walrus pups are almost triple the size they were at birth and begin to become more and more independent, although they tend to remain very close to their incredibly protective mothers until they are two or three years old.

Young females will often remain close to their mothers, but males begin to venture away from the herd to join all-male bachelor groups. Female Walruses can reproduce at around 6 or 7 years of age, but males are not mature until they are at least 10 years old and will often not successfully reproduce until they can prove their dominance around 5 years later.

Diet and Prey

Walruses are carnivorous animals that only hunt and eat other animals to survive. They have thick mustaches containing roughly 450 very sensitive whiskers that help them to find food in the dark and murky waters at depths of around 328 feet (100 meters) below the surface. Walruses find almost all of their prey on the ocean floor and are known to expel streams of both air and water into the sediment to reveal food hidden under the sand. They feed primarily by sucking food into their mouths rather than using their teeth to chew on it and are even known to grip shellfish between their lips and suck the soft creature out from inside the shell, before spitting the shell out into the water.

Walruses feed on a variety of different prey species including clams, snails, worms, squid, octopuses, and even some species of slow-moving fish. Some Walrus populations are also known to hunt seals.

Predators and Threats

Due to the large size and aggressive nature of these marine mammals, Walruses have few predators in their natural environments, except pods of Killer Whales and the occasional brave Polar Bear, as they can easily defend themselves with their enormous tusks. Humans are the most common predators of the Walrus as they are hunted for the meat, skin, and oil by local populations (along with the less desirable hunting of them for their ivory by non-native people). They are also threatened in certain areas by water pollution, including oil contamination that affects them directly but also through their prey, along with large fishing vessels that harvest the animals that the Walruses prey on and not only leave them with less food but also cause severe noise pollution in the normally quiet and remote waters.

Interesting Facts and Features

Walruses are incredibly well adapted to living in some of the coldest regions in the world, with thick skin that covers a thick layer of blubber (fat) that helps to keep them warm. Their enormous tusks were originally thought to aid them when feeding but are now known to be more to do with social status and even help with mobility. Walruses dig their tusks into ice floes to help them haul their enormous bodies out of the water but also anchor their tusks into the ice so they can sleep whilst their bodies remain submerged beneath the waves. Walruses are also known to use their long and powerful tusks like a pickaxe to carve their way through the thick ice.

They feed in the darkness of the ocean floor and are known to commonly dive to depths of between 262.5 feet (80 m) and 328 feet (100 m) for nearly half an hour at a time. However, recent studies show that depending on the availability of prey, Walruses have been known to reach much deeper depths of up to 590.6 feet (180 meters) below the surface of the water.

Relationship with Humans

For thousands of years, local people have thought of Walruses as being very similar to humans, as they are known to display qualities of intelligence, are slow to reproduce, and take long and very good care of their more vulnerable young.

Walruses have also been hunted by people in their native countries for thousands of years as a good source of food, but in more recent years they have also been increasingly hunted for the ivory in their tusks, which is considered to be second in both size and quality only to that of elephants. Large-scale hunting has decimated Walrus populations, particularly in certain areas, but it is also increasing amounts of pollution that are having a devastating effect on wild populations.

Conservation Status and Life Today

Today, the Walrus is considered to be a species that is Vulnerable in its natural environment, although data is hard to gather on these bottom-feeding mammals. They have been declining in number since the 18th century with increasing levels of hunting and human activity, and more recently are becoming increasingly threatened by the lessening amount of ice due to global warming. Although the exact population size is unknown, there are estimated to be between 200,000 and 250,000 individuals remaining in the freezing waters of the Arctic Circle.