Animal：The ''winged''swimmers - Harbour seals
【明報專訊】The family of seals are members of pinnipeds (鰭足亞目), which literally means ''winged-feet''. The ''wings'' of the seals are their flipper-like limbs, which make them awesome swimmers.
All about adaptation
Harbour seals are probably the pinnipeds with the broadest distribution. They can be found in coastal waters in the northern hemisphere. On a good day, they can be seen on rocks, beaches and mud flats where they can easily slip back into water to escape any threats on land.
Seals are not small creatures. An adult male harbour seal can measure close to two metres in length and weigh up to 170 kg. But do not be fooled by their sizes into thinking that they must be clumsy in movement. In fact, harbour seals have the bodies of ace swimmers.
Their flippers are long and flat, lined with webbed digits. With perfect coordination of their hind limbs and side-to-side movements of their streamlined body, harbour seals are agile in water. When swimming, they basically stop breathing. Their narrow nostrils (鼻孔) close under water. Their heart rates also slow down to conserve oxygen. Their large eyes with flat corneas (眼角膜) allow more light in, even in dark waters. And their whiskers (鬚) are super sensors which can detect sound waves to spot prey. If there is a need, harbour seals can remain underwater for up to 30 minutes!
Harbour seals also have adaptation for their time on land. Their fur protects their skin when hauling out, or gathering on land. Gland secretions keep their skin moist. They have thick layers of fat under their skin, which provide energy and insulation. These also give the harbour seals a higher metabolic rate at rest than most other land animals their size.
Let's play
Harbour seals are of a playful nature, whether pups or adults. Even though they are not very sociable, they play a lot, mostly by themselves. They also play with objects, such as large seaweed. What a wonderful thing to remain curious and fun-loving, like children!
Keep their home clean and safe
Harbour seals are solitary animals and only form small groups during pupping and moulting (fur-regrowth) seasons. Pups are nursed by mother seals with milk with a high fat content of 50%. This super nutrition allows them to grow up very fast. It also means that mother seals have to make frequent feeding trips. Safe and accessible sites on land are therefore important for a thriving harbour seal population.
Harbour seals haul out near the shore, where there are risks of polluted waters, as well as entanglement and capture in fisheries. Let's protect harbour seals by treating our waste carefully and keeping it away from the coasts and the seas!
Text and photos: Ocean Park Hong Kong
[Smarties' Power English 第297期]
