‘Many scientists don’t like to talk about shark sex,’ Juliet Eilperin writes in her entertaining study of sharks and their world. ‘They worry it will only reinforce the popular perception that these creatures are brutish and unrelenting.’ In as far as we understand the subject – only a few species have been observed mating – the business is ‘very rough’. Larger male sharks have to bite or trap the females to keep them around during courtship; marine biologists can tell when a female has been mating because her skin will be raw or bleeding. The process is so violent that, come the mating season, female nurse sharks will stay in shallow water with their reproductive openings pressed firmly to the sea floor. Otherwise they risk falling prey to roaming bands of males who ‘will take turns inserting their claspers in her’ (the clasper is the shark version of a penis, found in a pair behind the pelvic fins). A litter of fifty pups will have anything from two to seven fathers. But the reproductive story gets rougher still. A number of shark species go in for oophagy, or uterine cannibalism. Sand tiger foetuses ‘eat each other in utero, acting out the harshest form of sibling rivalry imaginable’. Only two babies emerge, one from each of the mother shark’s uteruses: the survivors have eaten everything else. ‘A female sand tiger gives birth to a baby that’s already a metre long and an experienced killer,’ explains Demian Chapman, an expert on the subject.

LRB 2 August 2012 | PDF Download