Whales and Seals Definitive
Whales and Seals Definitive
Whales and seals are the two groups of marine mammals to be found in the Southern Ocean, where they are an important part of the marine ecosystem. Severely exploited by man in the past they are now mostly protected. Some have seen dramatic population increases in recent decades, though others remain greatly reduced compared to pre-hunting levels.
Whales
Southern Ocean whales are migratory, heading to warmer waters during the Antarctic winter. Calves are born in these more hospitable seas and the whales return south in the austral spring. During this time they follow the receding ice edge which is an area of high biological productivity that provides a rich feeding ground.
There are two natural groups of whales: toothed and baleen.
Toothed whales
Toothed whales use ‘echolocation’ to navigate and find prey. They emit high-pitched clicks and sense them as they bounce back off objects.
The group includes more than 60 species. These vary in size from the largest being the sperm whale (£3.60) and the smallest being porpoises. The disparity in these is so large it would take one thousand porpoises to equal the body weight of a single sperm whale.
Between these two extremes are more than 20 species of beaked whale and many dolphins (which are in fact whales). The largest of these is the orca or killer whale (£5) that preys on fish, penguins, seals, and other whales. The largest population of orcas seems to be in Antarctica where it is estimated some 160,000 animals range. They typically live to be over 50 years and can swim up to 30 miles per hour in short bursts.
Baleen whales
The baleen whales, such as the fin whale (£1.40), southern right whale (£1.85) and humpback whale (£2), have fibrous plates of baleen instead of teeth, which they use to strain plankton and small fish from the seawater.
The most numerous baleen whale is the Minke whale (£1), a species that spends much of its time in the Antarctic near the ice-edge. The Minke was named for an infamous 18th-century Norwegian whaler who regularly broke the rules concerning the types and sizes of whales that he was permitted to hunt at that time. Soon all the small whales became known as ‘Minke’s whales’.
Minkes are the only baleen whale that are still hunted commercially. Japanese and Norwegian whalers kill a few hundred each year for scientific purposes and for meat. The Minke whale has a remarkable song that sounds very mechanical and caused some problems for military sonar listening for submarines during World War II.
Seals
There are also two natural groups of seals: true seals and eared seals, the latter comprising fur seals (50p) and sea-lions. At Bird Island alone there are 65,000 breeding fur seals. In fact, all seals have ears, but ‘eared’ seals differ in having a small external ear rather than just a small aperture on the side of the head.
Depending on species, seals feed on fish, squid and/or krill. Thick layers of blubber beneath the skin of both whales and seals act as a food reserve and insulation. All Antarctic seals also have a layer of fur, giving additional insulation when they are hauled out on land or ice.
Seals leave the water to breed, rest and moult. Of the six Antarctic species, four are ice-habitat specialists, breeding on the sea ice in spring. Ross (1p) and Leopard seals (74p) tend to be solitary, whereas Weddell (5p) and crabeater seals (10p) form loose breeding aggregations.
Weddell seals were named for the British Antarctic explorer James Weddell, who commanded British expeditions into the Weddell Sea (which is also named for him). They live farther south than any other mammal.
Weddell seals use their large, strong, forward-pointing canine teeth to chew breathing holes through cracks in the ice. They can dive over 2,000 feet deep and stay submerged for over an hour. They also have excellent eyesight, allowing them to navigate effectively in the dim light beneath Antarctic ice shelves.
The leopard seal is the largest of the true Antarctic seals and is the only seal that eat other seals. They have excellent senses of sight and smell under water.
Antarctic fur seals and elephant seals (80p) are both found north of the pack-ice zone and breed in dense colonies on beaches. Here, dominant males (bulls) maintain harems of females (cows) in territories. In constantly defending these cows, bulls will not forage at sea and instead they rely on blubber reserves laid down in the previous winter.
All seals breed annually and the timing of pup production and associated behaviour is linked to habitat and ecology.
Technical details:
Designer Andrew Robinson
Printer Cartor Security Printing
Process Lithography
Stamp Size 42 x 28mm
Perforation 13 ¼ x 13 ½ per 2cms
Sheet Layout 10
Release date 10 December, 2024
Production Co-ordination Creative Direction (Worldwide) Ltd