PINNIPEDS

Seals collectively belong to the order Pinnipedia and the thirty-three (33) species within this order are known as Pinnipeds. The name Pinniped originates from the Latin word meaning ‘fin-footed' (or wing-footed), which refers to their fin-like flippers. Pinnipeds are mammals, therefore they are warm blooded, breathe air and give birth to live young which are suckled and reared by their mother.

Classification of Pinnipeds

The thirty-three (33) species of Pinniped can be divided into three (3) distinct families. The first group is the family Phocidae, consisting of eighteen (18) species referred to as true seals or ‘earless seals' due to their lack of external ear flaps or pinnae. The second group is the family Odobenidae that is represented by one species, the walrus. The walrus is easily distinguished by its tusks and great size. Like the ‘true seals' the walrus has no external ear flaps. The third group is the family Otariidae, including the fourteen (14) species of fur seals and sea lions. Fur seals and sea lions are recognisable by their external ear flaps (pinnae). The fourteen species consists of nine species of fur seals and five species of sea lions.

Evolution of Pinnipeds

As with whales and dolphins, seals were once land-dwelling mammals that took to the sea approximately twenty million years ago. The seals did not evolve as fully aquatic mammals however, and must return to land (or ice) to bear and rear their pups; some species spend much of their time on land between feeding trips. Despite this fact, seals have undergone many changes or adaptations to become highly efficient and elegant swimmers.

Water is a very different medium to air, and is harder to move about in than air. Water is also an excellent conductor of heat which is why a land-based mammal, such as a human, can not spend extended periods in the ocean without losing a lot of body heat. Lastly, water is a great conductor of sound, which allows communication over long distances; particularly useful as seals have good hearing. So from this information it is clear that changes or adaptations were required for the seals' land-dwelling ancestors to become efficient in their new aquatic medium. Changes occurred to the body shape, method of locomotion, method of maintaining body temperature and the senses such as eyesight, hearing, vocalising underwater and their whiskers.

Body shape of a Seal

All seals have a sleek, elongated body shape rather like a torpedo. Their streamlined body shape evolved to create as little resistance as possible in water – a very dense element. The external appendages of seals have been reduced from those of their land ancestors. The head merges with the rest of the body without an obvious neck, in keeping with their sleek body shape. The fur, when wet, is very smooth to allow water to glide over it easily. The thick layer of blubber (fatty tissue) just beneath the skin aids streamlining by smoothing out the contours of the body and any structures that may protrude such as the skeleton.

Method of locomotion

In water seals become very buoyant. This effectively makes them weightless; suspended in their water environment. Therefore they do not require the supporting limbs that keep a land mammal's body clear of the ground. Seals modified their limbs by shortening the arm and leg bones now hidden within the body, however these are still very strong. The bones of the hands and feet have elongated and are bound together in a web-like structure of skin to form flippers. These paddle-like blades are streamlined like the wings of an aircraft and are perfect for propulsion.

Locomotion in Fur Seals and Sea Lions : The Otariid's (Fur Seals/Sea Lions) fore flippers are their main source of power when swimming. Their fore flippers are longer than their relations, the Phocids (true seals), with cartilage extending past the digits (finger bones) for extra length and strength. Fur Seals and Sea Lions sweep through the water with powerful down strokes of the fore flippers that rotate at the wrist joints allowing the streamlined flipper to cut through the water on the return stroke. The Fur Seals and Sea Lion's hind flippers are also elongated, with cartilage extending past the digits. Their toes are joined with a web of skin and strong nails are found on the inner three toes of the hind flippers, which are ideal for grooming. The hind flippers are used for steering (and sometimes for paddling in confined quarters), and when not in use are left to trail behind the body completing the streamlined shape.

On land, Fur Seals and Sea Lions are the most agile of all seals. They are able to turn their hind flippers forward for walking. For slow walking the fore flippers are moved alternately with the hind flippers being brought up together (almost to the fore flippers) and the belly being held clear of the ground. For faster movement on land, Fur Seals and Sea Lions can break into a gallop by moving the fore flippers together, arching the back and bringing the hind flippers up more quickly in a series of bounds. The roughened skin on their flippers provides grip on rocks or ice. If approaching a seal on the beach, it is important to note that if threatened the seal may become aggressive, and some species can out-run a human.

Locomotion in True Seals : The Phocid's (True Seal's) main source of power when swimming comes from its rear flippers and hind quarters. When swimming a true seal presses its fore flippers against its body, where there is a slight indentation in the blubber for the flippers, to complete the streamlined form. In Phocids, the fore flippers are generally smaller than Otariids (Fur Seals & Sea Lions), being short and blunt in comparison, with strong claws on each digit. The Antarctic phocids' fore flippers are longer and more pointed than the northern phocids' with less developed claws. True Seals propel themselves by alternate strokes of the hind flippers, which are spread to take advantage of the web on the power stroke and relaxed on the return stroke. In addition to their hind flippers, True Seals use side to side movements of their hind quarters, rather like that of a fish, to propel themselves. When moving slowly True Seals may swim differently, holding the fore flippers out from the body for stability.

True Seals have far less mobility on land than Fur Seals and Sea Lions. They crawl on their bellies in a caterpillar-like fashion, with the seal taking its weight on its chest while bringing the pelvic region forward. It then transfers its weight to the pelvic region while it thrusts its chest forward. As mentioned, True Seals have limited mobility on land, however on ice they are able to move much faster by sliding across the ice. They are said to be able to move across ice as fast as a person can run. Both sides of a True Seal's fore flippers and hind flippers are covered with fur and there is no definite sole on the flipper. The strong claws found on a True Seals fore flippers are used for grooming. Some True Seals use their claws for grip when hauling out on rock or ice and others may use their claws to scrape snow and ice to keep a breathing hole open or to create a breeding lair in the ice.

Maintaining body temperature

The normal body temperature of a mammal is 37 degrees Celsius, however water conducts heat at a greater rate than air, therefore a land mammal loses body heat very quickly when immersed in water. To overcome this problem seals have two important adaptations that help them to maintain a normal body temperature. Seals possess a thick layer of blubber below their skin, surrounding their entire body with the exception of the head and flippers. Blubber (fatty tissue) does not conduct heat well therefore it is an effective means of preventing heat loss from the seal's body. Most seals have a layer of blubber that is 7 – 10 cm thick. Blubber can also act as a food store, helping female seals to produce milk to feed their pups and allowing seals to go without food for periods when they come ashore to breed, give birth or moult. As the blubber does not cover the head and flippers of a seal, there is a need to reduce heat loss from these areas. This is done by reducing the blood flow to these areas, which in turn causes a reduction in heat loss. Blood flow may also be reduced to other areas of the body surface when required, particularly useful when diving at depths where the water is much colder.

Another adaptation that helps a seal retain heat is the layer of fur covering the body. Sea Lions and True Seals have a coat of fur (sometimes quite sparse in some species), but Fur Seals have developed this method of insulation further than the other seals. The fine hair fibres trap a layer of warm air around the roots, which provides insulation. The fine but dense hair or under fur is supported by stiff guard hairs that make up the outer coat. Glands in the skin produce oil that helps the fine tips of the under fur repel water, therefore the water only penetrates the guard hairs. This form of insulation is effective on land and when nearer to the surface of the water, however at greater depths the pressure of the water pushes the trapped layer of air out, reducing insulation. Blubber is far more effective in these situations.

The Senses

Seals have excellent senses. Their eyesight is particularly good and this is especially useful underwater where light levels are low. It is said that seals only see in black and white, which gives them better vision in low light environments. Seals have large eyes that are almost spherical in shape. The large size of their eyeballs enables the eye to take in more light, therefore providing them with excellent low light vision. A seal's vision is equally as important on land as under the water. On land a seal's sight is important to assess the intentions of an intruder by the way it moves and its posture, and to look out for signs of danger. When out of water, seals often have to cope with very bright light conditions. To protect their sensitive eyes, a seal's pupil contracts to a tiny pinhole. This protects the eye from the increase in light but does not effect the eyesight. A seal's eyes are also protected by secretions, which look like oily streaks as it runs from the eyes.

As with their eyesight, a seal's hearing is highly developed both in and out of the water. The bones of a seal's middle ear are much larger than those of a land mammal, and seals can pin point the location of a sound underwater quite precisely. The Weddell Seal

can produce calls underwater that can be heard 30 kilometres away by other seals. On land seals are very vocal when communicating with each other. Hearing is an important sense on land, for instance a female seal and her pup use calls to enable them to distinguish each other from the rest of the mothers and pups. Male seals (bulls) make roaring sounds to establish dominance and territorial boundaries. The various species produce a wide range of sounds from grunting, barking and clicking to howling, rumbling, shrill chirping sounds and even eerie bell-like calls.

Seals use their extremely sensitive whiskers to detect vibrations underwater such as the movements of a fish swimming. This enables them to catch prey in the dark or in environments where there is little visibility. Seals push their whiskers forward when hunting and capturing their prey to allow successful detection of its vibrations. The whiskers are highly efficient for capturing prey, as it has been known that a seal, which was blind in both eyes, was still able to catch more than enough food for itself and remain healthy. The whiskers are also used on land for interaction between individuals. If the whiskers are held forward it is usually a sign of aggression. A female seal may also drive off the unwanted attention of a bull seal by attempting to bite its whiskers which irritates them, often causing the bull to retreat. During the Pet Porpoise Pool show, when a seal balances a ball on its nose, it uses its whiskers to sense the movement of the ball allowing the seal to keep it perfectly balanced.

While a seal's sense of smell is not used underwater as the nostrils are sealed, smell is said to be an important sense for seals on land. Seals often have a strong scent, particularly breeding males, which indicates that smell plays some part in social interactions. Further evidence that smell is important is that, as well as vocalisation, a mother seal will smell her pup if it has been separated from her to recognise it as her own.

Moulting

Like all mammals, a seal's hair needs renewing at certain intervals; therefore the process of moulting takes place. Moulting is more obvious in true seals than fur seals and sea lions. Fur Seals and Sea Lions lose their old coats and renew them gradually; therefore moulting is not so noticeable. True Seals, on the other hand, replace their coat every season over a short period. Fur and skin is shed in bits and pieces, often leaving the seal looking very untidy. Blood supply to the skin increases where the new coat is growing, so many species of true seal spend time huddled together on land during moulting to avoid great heat losses.

Reproduction and breeding behaviour

Fur Seals often choose rocky beaches safe from storm tides for breeding grounds, whereas Sea Lions tend to prefer sandy beaches, and True Seals choose to breed either on sandy beaches, or in cracks or holes in ice depending on the species. For Phocids and Otariids there is competition within the breeding males to establish a hierarchy and determine territorial boundaries, or with some species, to maintain exclusive access to a female. This is done by displays and loud vocalisations, or by engaging in fights. The females (cows), in many species, instinctively return to the colony where they were born to give birth to their own pups. It is usually the females that decide which territory, within the colony, they will give birth and mate in rather than the bulls choosing a heirem.

The reproductive cycles of Phocids and Otariids differ in that, although gestation periods (mating to birth) are generally the same being an annual cycle, the beginning of this cycle may occur in different months for different species or individuals. There are two exceptions to this and they are the Australian Sea Lion and the Walrus who both have unique breeding cycles. The Australian Sea Lion has a gestation period of eighteen months and the Walrus has a gestation period of fifteen months. The basic process however, is the same for all other species of seals. This begins with mating approximately 6 – 20 days (depending on the species) after giving birth, when the cows come into oestrus (heat). The cows continue to rear their newborn pups. After mating and fertilisation of the egg, there is a period of approximately three months where implantation of the egg is delayed. The delay allows births and mating to occur at the same time, when males and females congregate on land together which can be a dangerous time for many seals. The delay gives the cow time to recover from the initial strain of lactation and rearing a young pup before the new embryo begins to develop.

FUR SEALS Family Otariidae

The nine species of Fur Seals all possess a thick, luxurious layer of under fur. It was this under fur (and their blubber) that made them an attractive target for hunters, who reduced some species to near extinction. It was not until seal products began to be traded on a commercial basis that population numbers were reduced substantially. In the 1960's, film and television companies began broadcasting seal hunts, which raised the awareness of the general public by showing the harsh reality of the slaughter and skinning of seals. Despite this, it took many years for the world to come to its senses and for the hunting of seals to be banned for most species, or strictly controlled. The populations of some species have recovered well since hunting was banned, however some species still have dangerously low numbers. Fur Seals, Sea Lions and True Seals have all suffered at the hands of hunters throughout history.

The Fur Seals are divided into two genera. There are eight species in the genus Arctocephalus, which are known as the Southern Fur Seals. The Northern Fur Seal is the only species in the second genus, Callorhinus.

All the Southern Fur Seals look quite similar. Adult males are larger than the females in all species, and the males also possess a thick mane of fur around the neck and shoulder area. The largest of all the Fur Seals are the Cape and Australian Fur Seals, which are actually classified as the same species but divided into two sub-species. The smallest of the Fur Seals is the Galapagos Fur Seal.

CLASS Mammalia

ORDER Pinnipedia

FAMILY Otariidae

SUBFAMILY Arctocephalinae

GENUS Arctocephalus

SPECIES pusillus

SUBSPECIES doriferus

This fur seal is considered to be the same species as the Cape Fur Seal Arctocephalus pusillus pusillus, but the species is divided into two subspecies due to the different distribution of both seals. This seal is one of the largest of all the Fur Seals.

Australian Fur Seals are found in South-eastern Australian waters, mainly around Tasmania and Victoria, and may also be found off Southern New South Wales. The major breeding colonies, of which there are approximately ten colonies, are situated in Bass Strait between Victoria and Tasmania. There is only one colony in New South Wales, which is located at Seal Rocks, North east of Sydney. Australian Fur Seal pups are born between November and February, with mating occurring approximately one week after each female gives birth.

There are no completely accurate counts of Australian Fur Seals, however it is estimated that approximately 10,000 pups are born each year and that there are probably 40,000 Australian Fur Seals in total. It is thought that the population of this species is not increasing substantially, which may be due to inadequate feeding conditions.

LENGTH Males 2.3m – 2.7m Females 1.2m – 1.7m

WEIGHT Males: up to 360kg Females: up to 110kg

DIET Fish, small penguins, squid, octopus

APPEARANCE Large, dusty grey-brown seal. Has darker markings on the back, and is paler on its under parts. Variations in colour do occur.

NEW ZEALAND FUR SEAL Arctocephalus forsteri

CLASS Mammalia

ORDER Pinnipedia

FAMILY Otariidae

SUBFAMILY Arctocephalinae

GENUS Arctocephalus

SPECIES forsteri

New Zealand Fur Seals breed on many islands off the west coast of New Zealand, with colonies found from Open Bay to Fiordland in the south-west. Colonies are also found on islands south of New Zealand. This species also occurs in Australia where breeding colonies are situated at Kangaroo Island, off the South Australian coast, and along the south-western coast of Australia. New Zealand Fur Seal Pups are born between December and February, with the peak being in December. The total population of New Zealand Fur Seals is estimated at about 60,000 individuals. Between 5,000 and 10,000 of these are found in Australia.

LENGTH Males: 1.45m – 2.2m Females: 1.25m – 1.8m

WEIGHT Males: up to 180kg Females: up to 80kg

DIET

APPEARANCE Smoky grey back and flanks, fading to a dusty brown. Under parts are paler. Variations in colour occur.

SEA LIONS Family Otariidae

There are five species of sea lion, which are generally larger than the fur seals with the exception of the Australian and Cape Fur Seals. Sea lions possess a much coarser fur than fur seals and they lack the luxurious under fur of Fur Seals. Similarly to the Fur Seals, male Sea Lions are larger than the females. Adult male Sea Lions have a thick mane of fur around the shoulders. Sea Lions can often be found sharing their environment with Fur Seals, however they have limited contact with each other as they prefer different hauling out sites, even though they may be on the same beach.

CALIFORNIAN SEA LION Zalophus californianus CLASS Mammalia ORDER Pinnipedia FAMILY Otariidae SUBFAMILY Otariinae GENUS Zalophus SPECIES californianus

Californian Sea Lions are one of the most familiar of the Pinnipeds due to its popularity as a trained seal. Californian Sea Lions are particularly easy to train and possess a lively nature.

The Californian Sea Lion has been divided into three subspecies due to their different geographical ranges. The Californian Sea Lion (Zalophus californianus californianus) is the sea lion of the Pacific Coast of North America from Vancouver Island to Tres Marias Islands off Mexico, with breeding colonies on many small offshore islands of California and the Sonoran Coast of Mexico. There are approximately 75,000 sea lions found off the coast of North America and the population is flourishing.

Zalophus californianus wollebaeki is the sea lion found on the Galapagos Islands. There appears to be few physical differences between the Galapagos Sea Lions and those found off the coast of California. They are found on all the Galapagos Islands and breed on most of them as well. The population in the Galapagos is stable and estimated at about 40,000 individuals.

Zalophus californianus japonicus was the sea lion commonly found on islands in the Sea of Japan at the beginning of this century. There have been no sightings of these sea lions in recent times, however it may be possible, though doubtful, that there are specimens still in existence on remote islands in the Sea of Japan.

Pups are born from May onwards, with a peak in births during June. Mating occurs two weeks after individuals give birth.

AUSTRALIAN SEA LION Neophoca cinerea CLASS Mammalia ORDER Pinnipedia FAMILY Otariidae SUBFAMILY Otariinae GENUS Neophoca SPECIES cinerea LENGTH Males: 2m - 2.7m Females: up to 2m WEIGHT Males: up to 350kg Females: up to 110kg

APPEARANCE Varies from dark grey-brown to black. Females are often lighter in colour than males. Mature males possess a high bony crest on the forehead.

Australian Sea Lions are of similar size to the Californian Sea Lions. They are found off the South and south-west coasts of Australia. Before commercial sealing, Australian Sea Lions could be found as far east as Bass Strait, however this is not the case today.

The breeding colonies are inhabited from October onwards, with a peak in births of pups in late November and December. The Australian Sea Lion has a unique breeding cycle with an eighteen month gestation period (mating to birth). Most other seals have an annual cycle, apart from the Walrus whose gestation period is fifteen months.

As the male Australian Sea Lion matures it becomes darker and develops white to yellowish guard hairs on the top of the head and down the neck to the shoulders. It is for this reason that these sea lions are often referred to as ‘Australian White-Capped Sea Lions'.

The total population is said to be about 10,000, with possibly two thirds of the population located in Western Australia. Australian Sea Lions are protected in Australian and while quite small, the population is stable.

LENGTH Males: 2m – 2.5m Females: 1.7m – 2m

WEIGHT Males: 180 – 350kg Females: 80 – 105kg

DIET Fish, Little Penguins, Squid, Crayfish, Octopus

APPEARANCE Often shows greater colour variation than most Otariids. Females are silver-grey to fawn on the back and generally pale yellow or creamy underneath. Males are born with dark brown fur. After the moult they resemble the female in colour for the first two years. As the male ages it becomes darker and develops white to yellowish guard hairs from the top of the head to the shoulders. Males are large and stocky.

TRUE SEALS Family phocidae

Phocids can be divided into two subfamilies, Phocinae and Monachinae. The subfamily Phocinae (Northern Phocids) are found mainly in the Arctic and surrounding areas. The subfamily Monachinae (Southern Phocids) are found in warmer tropical waters and the Antarctic.

The Northern Phocids consist of nine species, all of which have well developed claws on their front and hind flippers. The Southern Phocids, also consisting of nine species, all have relatively small claws. The Northern Phocids have three incisor teeth on either side of the upper jaw, whereas the Southern Phocids have two incisors on either side of the upper jaw and two below, with the exception of the Elephant Seals who have one tooth on either side of the lower jaw.

LEOPARD SEAL Hydrurga leptonyx

Leopard Seals are mainly solitary animals that possess a ferocious reputation. When approached, these seals open their mouths widely to reveal their large, sharply pointed teeth in a threatening manner. Leopard Seals predominantly eat red meat; their main food source being penguins, other sea birds and on occasion they prey on the young of other seals. The Leopard Seal can be found from the shores of the Antarctic continent to the Sub-Antarctic Islands. In summer they are found on the northern edge of the Antarctic pack-ice. In winter they move north to the Sub-Antarctic and cool temperate islands. Leopard Seals are frequently seen near Patagonia, the Falkland Islands, New Zealand, Tasmania and southern Australia.

Most Leopard Seals breed on the pack-ice. Pups are born from September to January, with the peak in births occurring in November and December.

The total population of Leopard Seals is estimated between 250,000 and 500,000 individuals.

LENGTH Males: 2.5m – 3m Females: 3m – 3.6m

WEIGHT Males: 270 – 400kg Females: 370 – 500kg

DIET Penguins, other sea birds, young seals, krill, fish, squid

APPEARANCE Silver-grey to black on the back and silver or creamy underneath. They possess slate-grey spots on the underside and the reverse on the back where paler spots occur. Leopard Seals have a long neck with a reptile-like head. The females of this species are larger than the males, which is the opposite of most seal.