and are accompanied by well-developed gill rakers, smaller eyes, much larger overall size and smaller average girth. Great whites possess large, dagger-like teeth; basking shark teeth are much smaller and hooked; only the first three or four rows of the upper jaw and six or seven rows of the lower jaw function. In behaviour, the great white is an active predator of large animals and not a filter feeder. Other distinctive characteristics include a strongly keeled caudal peduncle, highly textured skin covered in placoid scales and a mucus layer, a pointed snout—distinctly hooked in younger specimens—and a lunate caudal fin. In large individuals, the dorsal fin may flop to one side when above the surface. Colouration is highly variable (and likely dependent on observation conditions and the individual's condition): commonly, the colouring is dark brown to black or blue dorsally, fading to a dull white ventrally. The sharks are often noticeably scarred, possibly through encounters with lampreys or cookiecutter sharks. The basking shark's liver, which may account for 25% of its body weight, runs the entire length of the abdominal cavity and is thought to play a role in buoyancy regulation and long-term energy storage. Life history Basking sharks do not hibernate, and are active year-round. In winter, basking sharks often move to deeper depths, even down to and have been tracked making vertical movements consistent with feeding on overwintering zooplankton. Surfacing behaviors They are slow-moving sharks (feeding at about ) and do not evade approaching boats (unlike great white sharks). They are not attracted to chum. Though the basking shark is large and slow, it can breach, jumping entirely out of the water. This behaviour could be an attempt to dislodge parasites or commensals. Such interpretations are speculative, however, and difficult to verify; breaching in large marine animals such as whales and sharks might equally well be intraspecific threat displays of size and strength. Migration Argos system satellite tagging of 20 basking sharks in 2003 confirmed basking sharks move thousands of kilometres during the summer and winter, seeking the richest zooplankton patches, often along ocean fronts. They shed and renew their gill rakers in an ongoing process, rather than over one short period. A 2009 study tagged 25 sharks off the coast of Cape Cod, Massachusetts, and indicated at least some migrate south in the winter. Remaining at depths between for many weeks, the tagged sharks crossed the equator