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

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 Niño/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.