The grey seal is Britain's largest carnivorous mammal. Its thick, insulating layer of blubber and waterproof fur allow it to survive in cold water temperatures.

The solitary hunter

When at sea, grey seals hunt alone; it is only on land that they congregate, often in their thousands. The seal's large eyes enable it to see well in dark, murky waters, but it uses its highly sensitive ears mostly when hunting for its prey. Even a blind seal has no trouble catching prey. You cannot easily see a grey seal's ears because there are no external ear flaps. The seal can close its ear openings when diving to keep water out.

As well as the ears, the seal's sensitive whiskers help it to detect prey, feeling the slightest vibration. Once a fish has been detected, the grey seal gives chase, its streamlined body allowing it to swim fast and with agility. It is possible that fish can be followed by sensing changes in the chemical composition of the water.

A wide variety of open-sea and bottom-dwelling fish is eaten and in coastal waters, salmon, herring and flatfish are the types most commonly eaten. Occasionally, squid and crabs are eaten too.

The grey seal is able to stay underwater for up to 16 minutes, although five to ten minutes is more normal. A land-living mammal is unable to breathe underwater for so long, but the grey seal can do this because its blood contains high amounts of haemoglobin (the red blood pigment that carries oxygen around the body). The seal's heart rate slows down considerably during a long dive in order to conserve oxygen.

Read More: Breeding

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