Movements, habitat use and feeding success of cultural clans of South Pacific sperm whales

Summary 1 The population of sperm whales (Physeter macrocephalus) in the South Pacific is divided into at least five sympatric vocal clans that almost certainly reflect cultural variation. 2 We investigated differences in movements and feeding success of groups from different clans off the Galapagos Islands and northern Chile, using data from 87 days spent tracking groups of known clan. 3 Groups from different clans showed different use of habitat and movement patterns. Off the Galapagos Islands, ‘Plus-one’ clan groups moved in relatively straight lines while ‘Regular’ clan groups had more convoluted tracks and a more inshore distribution, patterns which were consistent across years. 4 Groups from different clans had different defecation rates, indicating between-clan variation in feeding success. Off the Galapagos Islands, ‘Plus-one’ clan groups were more successful in the depauperate ENSO (‘El Nino/Southern Oscillation’) conditions of 1987. However, in the cooler conditions of 1989, groups of the ‘Regular’ clan had much higher feeding success than those of the ‘Plus-one’ clan. 5 Thus we suggest that cultural inheritance in sperm whales incorporates foraging strategy as well as vocal patterns, and that clan membership has fitness consequences. 6 That clans seem differentially affected by altered climate conditions has implications for the effects of global warming on sperm whales. 7 The results also support the hypothesis that culturally determined differences in fitness may have affected genetic evolution through the process of cultural hitchhiking.