The sand tiger shark is one of the best-studied of the shark species. They are the only sharks known to gulp air at the surface and store it in their stomach to provide buoyancy (2). These sharks generally mate between October and November and courtship can take a long time, with the male aggressively nipping his potential mate (3). Females are ovoviviparous, giving birth to two large pups every two years. Pups hatch out of their eggs within the oviduct of the mother's reproductive system, one in each oviduct, and then feed on eggs that the female continues to produce (6). Over nine months to a year, the pups grow within their mother feeding on hundreds to thousands of eggs (6) and, by the time they are born, measure up to a metre long (3). During the day they are found near caves and ledges (5), hovering just above the surface either singly or in small groups (3). These fairly docile sharks are sluggish and, despite a ferocious reputation, feed mainly on fish (5).