Summary: Guttridge et al. (2009)

Sharks are often seen to associate in groups, but the structure (composition and organization) of these groups is unknown. Guttridge et al. (2009) aimed to quantify the social preferences of juvenile lemon sharks Negaprion brevirostris that live in close association with heterospecific nurse sharks Ginglymostoma cirratum. Juvenile lemon sharks associated with conspecifics in binary choice field experiments. Guttridge et al. (2009) found that 2-3 year old lemon sharks preferred groups of size-matched individuals and associated with conspecifics more than with heterospecifics. Their study provides further information on group-joining decisions and suggest that active mechanisms play a role in shark group formation and structure. Furthermore, shark associations provide opportunities for investigating social learning and cooperation in these fish.