Читать книгу Nature’s Babies - Mike Dilger - Страница 15

Surely one of the most celebrated of all beasts among whale-watchers because of their ability to virtually leap clear of the water and their haunting songs, the humpbacks are also thought to carry out the longest migration of any mammal. Each year they will travel from their summer feeding areas in the higher latitudes to breed and give birth in tropical waters during the winter – a round trip of over 16,000 km (10,000 miles).

The humpback is found in all the major oceans and can reach an impressive 12 to 17 m (39 to 55 ft) in length. Their knobbly flippers are immensely long and can be used, together with the colour of the underside of the tail, to identify different individuals. Humpbacks only feed on krill and small shoaling fish in the summer, before living off their fat reserves during the breeding season. When feeding, they are capable of working cooperatively using a technique called ‘bubble-netting’: a number of whales will drive a shoal of fish into a tight cylinder of underwater bubbles, before piling in, mouth agape, to swallow – in just a few gulps! – thousands of fish filtered from the water by special baleen plates.

The male humpbacks are particularly vocal, and are capable of producing loud and complex ‘songs’ by forcing air through their nasal cavities. It is not understood if this is used by breeding males to try and intimidate other males or attract females, or even if it serves another function entirely. Groups of males will often compete for the females, and on their return to the tropics twelve months later, the females will give birth to a 5 m (16 ft) long, 700kg (1,500 lb) calf. The young calf will then be a constant shadow beside its mother until weaned a year later.