The leopard seal is an amazing creature that lives in Antarctic waters. Although these seals play a unique role in the Antarctic ecosystem, they are often misunderstood as a species. There are many interesting aspects of this formidable Southern Ocean predator to be aware of. This type of seal is almost at the very top of the food chain. It got its name because of its characteristic coloration.
Origin of the species and description
It has long been assumed that the marine mammals of the pinniped group are descended from a common land-dwelling ancestor, but so far no clear evidence of this has been found. The discovered fossils of the species Puijila darwini, which lived in the Arctic during the Miocene (23-5 million years ago), provided that missing link. A well-preserved skeleton was found on Devon Island in Canada.
He measured 110 cm from head to tail and had webbed feet instead of the fins his modern descendants sport. Webbed feet would have allowed it to spend some of its time hunting for food in freshwater lakes, making land travel less awkward than flippers in winter, when frozen lakes would have forced it to forage on solid ground. The long tail and short legs made it look like a river otter.
Video: Leopard seal
While land animals are thought to have originally descended from marine life, some are, for example, ancestors of whales, manatees, and walruses — eventually crawled back into aquatic habitats, making these transitional species such as Puijila an important chain in the evolutionary process.
The French zoologist Henri Marie Ducrotay de Blainville was the first to describe the leopard seal (Hydrurga leptonyx) in 1820. It is the only species in the genus Hydrurga. Its closest relatives are the Ross, crabeater and Weddell seals, known as Lobodontini seals. The name Hydrurga means “water worker” and leptonyx — it means “little claw” in Greek.
Appearance and Features
Compared to other seals, the leopard seal has a pronounced elongated and muscular body shape. This species is known for its massive head and reptile-like jaws, which allow it to be one of the top predators in the environment. A key feature that is hard to miss is the protective coat, with the dorsal side of the coat being darker than the ventral side.
Leopard seals have a mixed coat of silver to dark gray, which makes up the characteristic “leopard” coloration with a spotted pattern, while the ventral (underside) side of the coat has a lighter color — from white to light grey. Females are slightly larger than males. The total length is 2.4–3.5 m, and the weight — from 200 to 600 kg. They are about the same length as the northern walrus, but the weight of leopard seals is less by almost half.
The ends of the leopard seal's mouth are constantly curled up, giving the illusion of a smile or a menacing grin. This involuntary facial expression adds a frightening look to the animal and cannot be trusted. These are potentially aggressive predators that constantly monitor their prey. On the rare occasions when they go out on land, they protect their privacy by emitting a warning growl at anyone who is too close.
The streamlined body of the leopard seal allows it to gain great speed in the water by striking in sync with its greatly elongated forelimbs . Another notable feature of — short, crisp whiskers that are used to study the environment. Leopard seals have a huge mouth relative to their body size.
The front teeth are sharp, like those of other carnivores, but the molars are connected to each other in such a way as to sift krill from the water, like a crabeater seal. They do not have external auricles or ears, but they do have an internal ear canal that leads to an external opening. Hearing in the air is similar to human hearing, and the leopard seal uses its ears along with its whiskers to track prey underwater.
Where does the leopard seal live?
These are pagophilic seals whose life cycle is completely connected with the ice cover. The main habitat is the Antarctic seas along the perimeter of the ice. Adolescent specimens are observed on the shores of subantarctic islands. Stray leopard seals have also been recorded on the coasts of Australia, New Zealand, South America and South Africa. In August 2018, one individual was sighted at Geraldton on the west coast of Australia. Leopard seals are denser in West Antarctica than elsewhere.
Fun fact: Lonely male leopard seals prey on other marine mammals and penguins in the ice-bound Antarctic waters. And when they are not busy looking for food, they can drift on ice floes to rest. Their outer coloration and unmistakable smile make them easily recognizable!
Most of the members of the genus remain inside the pack ice throughout the year, being in complete isolation for most of their lives, with the exception of the period when they are with their mother. These matrilineal groups may move further north during the Australian winter to the subantarctic islands and coastlines of the southern continents to provide proper care for the young. While solitary individuals may appear in areas of lower latitudes, females rarely breed there. Some researchers believe this is due to offspring safety issues.
What does a leopard seal eat?
Leopard seal — it is the dominant predator of the polar region. Developing a speed of up to 40 km/h and diving to a depth of about 300 m, he leaves his prey with little chance of salvation. Leopard seals have a very varied diet. Antarctic krill make up about 45% of the total diet. The menu may vary depending on the location and the availability of tastier prey items. Unlike other members of the family, the diet of leopard seals also includes Antarctic marine mammals.
The most common victims of the leopard seal's insatiable appetite are:
- crabeater seal;
- Antarctic fur seal;
- eared seal;
- Weddell seal;
The resemblance to the feline namesake is more than just skin coloring. Sea leopards — the most formidable hunters of all seals and the only ones that feed on warm-blooded prey. They use their powerful jaws and long teeth to kill prey. They are efficient predators that often wait underwater near the ice shelf and catch birds. They can also rise from the depths and grab birds on the surface of the water in their jaws. Clams — less dramatic prey, but an important part of the diet.
Fun fact: Leopard seal — the only seals known to regularly prey on warm-blooded prey.
A curious incident happened to photographer Paul Nicklen, who, despite the danger, was the first to dive into Antarctic waters to capture leopard seals in their natural environment. Instead of an evil sea demon, he encountered a cute female leopard who probably thought she was looking at a stupid baby seal.
For several days, she brought live and dead penguins as food for Niklen and tried to feed him, or at least teach him how to hunt and feed himself. To her dismay, Niklen wasn't too interested in what she had to offer. But he got some phenomenal photos of an intriguing predator.
Character and lifestyle features
Studies show that, on average, the aerobic diving limit for young seals is about 7 minutes. This means that leopard seals do not eat krill during the winter months, which is a major part of the diet of older seals as krill are found deeper. This can sometimes lead to joint hunting.
Interesting fact: There have been documented cases of cooperative hunts for Antarctic fur seals, conducted by a young seal and possibly its mother helping her grown pup, or may be the interaction of a female + male pair to increase the productivity of the hunt.
When a leopard seal gets tired of eating but still wants to have fun, it can play cat and mouse with penguins or other seals. When the penguin swims to the shore, the leopard seal cuts off his escape route. He does this over and over until the penguin either manages to make it to shore or succumbs to exhaustion. There seems to be no point in this game, especially since the seal uses up a huge amount of energy in this game and may not even eat the animals they kill. Scientists have suggested that this is clearly for sport, or perhaps it could be young, immature seals who want to hone their hunting skills.
Sea leopards have very poor contact with each other. As a rule, they hunt alone and never meet more than one or two other members of their species at the same time. An exception to this solitary behavior is the annual breeding season from November to March, when several individuals will cluster together. However, due to their exceptionally obnoxious behavior and solitary nature, little is known about their full reproductive cycle. Scientists are still trying to figure out how leopard seals choose their mates and how they define their territories.
Social Structure and Reproduction
Because leopard seals live in places that are difficult for humans to reach, little is known about their breeding habits. However, their breeding system is known to be polygamous, meaning that males mate with multiple females during the mating season. A sexually active female (aged 3–7 years) can give birth to one calf in the summer by coming into contact with a sexually active male (aged 6–7 years).
Mating takes place from December to January, shortly after weaning the grown calf, when the female is in oestrus. Preparing for the birth of seals, females dig a round hole in the ice. A newborn cub weighs about 30 kg and stays with its mother for a month before it is weaned and taught to hunt. The male seal does not take part in caring for the young and returns to his solitary lifestyle after the mating season. Most leopard seal breeding takes place on the pack ice.
Fun fact: Mating takes place in the water and the male then leaves the female to care for the cub she gives birth to after 274 days of gestation .
It is believed that the soundtrack is very important during breeding, as males are much more active at this time. These vocalizations have been recorded and are being studied. While little is known about why these sounds are made by males, they are believed to be related to aspects of their breeding and reproductive behavior. Hanging upside down and swaying from side to side, adult males have characteristic, stylized postures that they reproduce with unique consistency and are believed to be part of their breeding behavior.
From 1985 to 1999, five research cruises were made to Antarctica to study leopard seals. The seal pups were observed from the beginning of November to the end of December. The scientists noticed that there were about one pup for every three adults, and they also saw that most females stayed away from other adult seals during that season, and when they were seen in groups, they showed no signs of interaction. The mortality rate of leopard cubs during the first year is close to 25%.
Natural enemies of leopard seals
It is not easy to live long and healthy lives in Antarctica, and leopard seals are lucky to have not only an excellent diet, but also an almost complete absence of predators. Orcas — the only established predator of these seals. If these seals manage to escape the wrath of a killer whale, they can live up to 26 years. While not the largest mammal in the world, leopard seals can live an impressively long time given their stressful and rugged habitat. In addition to killer whales, small individuals of the leopard seal can try to hunt: large sharks and, possibly, seals. The fangs of the animal are 2.5 cm.
Trying to study these creatures can be dangerous, and in one case, a leopard seal is known to have killed a man. Not too long ago, a marine biologist working for the British Antarctic Survey drowned after being dragged nearly 200 feet (61 m) below the water by a seal. It is currently unclear whether the leopard seal intended to kill the biologist, but most importantly — it is a sobering reminder of the true nature of these wild animals.
When hunting penguins, the leopard seal patrols the waters at the ice edge, almost completely submerged, waiting for the birds to head towards the ocean. It kills swimming penguins by grabbing their legs, then vigorously rocking the bird and repeatedly slamming its body against the surface of the water until the penguin dies. Previous reports of the leopard seal cleaning its prey prior to feeding have been found to be incorrect.
Lacking the teeth needed to cut its prey into pieces, it swings its prey from side to side, tearing it into smaller pieces. At the same time, krill are eaten by suction through the seal's teeth, allowing the leopard seals to switch to different feeding styles. This unique adaptation may indicate the success of the seal in the Antarctic ecosystem.
Population and species status
After the crabeater and Weddell seals, the leopard seal is the most numerous seal in Antarctica. The estimated population of this species ranges from 220,000 to 440,000 individuals, ranking leopard seals as “Least Concern”. Despite the abundance of leopard seals in Antarctica, they are difficult to study with traditional visual methods because they spend long periods underwater during the Australian spring and summer when visual surveys are traditionally conducted.
Their special ability to create sound compositions underwater for long periods made it possible to create acoustic surveys, which helped researchers understand many of the animal's personality traits. Leopard seals — predators of the highest order, representing a potential risk to humans. However, attacks on humans are rare. Examples of aggressive behavior, harassment and attacks have been documented. Notable incidents include:
A great leopard seal is attacked by Thomas Ord-Lees, a member of the “Trans-Antarctic Expedition 1914-1917”, while the expedition was camping on sea ice. A leopard seal about 3.7 m long and weighing 500 kg was chasing Ord-Lee on the ice. He was only saved when another expedition member, Frank Wild, shot the animal.
In 1985, Scottish explorer Gareth Wood was bitten twice in the leg when a leopard seal tried to drag him off the ice and into the sea. His companions managed to save him by kicking him in the head with spiked boots. The only recorded death was in 2003, when a leopard seal attacked diving biologist Kirsty Brown and dragged him underwater.
In addition, the leopard seal has shown a tendency to attack black pontoons from rigid inflatable boats, after which it was necessary to equip them with special safety devices to prevent punctures.