Swim like a fish

Cormorants specialise in underwater attack. They are designed to move easily between air and water. Their feet are webbed and set back on the body to help them swim and dive. Special feathers let water in fast, expelling air so they can submerge quickly. But a cormorant's greatest attribute is its eyes. Above water the pupil is small, restricting the amount of light entering the eye. A greater cormorant's eye shows how tiny the pupil is. But a split second after the head is submerged the pupil expands to let in more light, and the lens changes shape. It sees clearly even in dark or cloudy water. The chase is on. Slowing their heart rate by half and reducing their need for oxygen by 90% cormorants can stay under water for minutes at a time. They become target-seeking submarines. The fish dart away, but are soon exhausted and the cormorant easily chases them down. Their diving expertise allows cormorants to go further out and chase larger fish, where sometimes the rewards can be magnificent.

Credits

Role Contributor
Editor-in-chiefPeter BASSETT
Editor-in-chiefDavid WALLACE
ProducerMary COLWELL
NarratorJohn HANNAH

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