Behavior

Head of a basking shark.

Studies in 2003 have disproved the idea that basking sharks hibernate and have shown that they are active throughout the year.^[6] In winter, basking sharks move to deeper water (depths of up to 900 m) feeding on deep water plankton. Satellite tagging confirmed that basking sharks move thousands of kilometres during the winter months locating plankton blooms.

A study published in 2009, in which 25 basking sharks were tagged off the coast of Cape Cod, Massachusetts, indicated that at least some individuals in the North Atlantic migrate south in the winter. Remaining at depths between 200 metres (660 ft) and 1,000 metres (3,300 ft) for many weeks, the tagged sharks traveled as far south as Brazil, crossing the equator. One individual spent a month in the waters near the mouth of the Amazon River. It is unknown why the sharks undertake this journey. The lead author of the study, Gregory Skomal of the Massachusetts Division of Marine Fisheries, suspects it may be related to the shark's reproduction. ^{[5] [7]} It was also found that basking sharks shed and renew their gill rakers in an ongoing process, rather than over one short period.

They feed at or close to the surface with their mouths wide open and gill rakers erect. They are slow-moving sharks (feeding at about 2 knots) and do not attempt to evade approaching boats (unlike great white sharks). They are harmless to humans if left alone and will not be attracted to chum.

Basking sharks are social animals and form schools segregated by sex, usually in small numbers (3 or 4) but reportedly up to 100 individuals.^[4] Their social behaviour is thought to follow visual cues, as although the basking shark's eyes are small, they are fully developed and have been known to visually inspect boats, possibly mistaking them for conspecifics.^[8] Females are thought to seek out shallow water to give birth.