Social organization of sperm whales off the Galapagos: implications for management and conservation.

Groups of females Physeter macrocephalus resided in the study area for at least 2 months. The groups were attended from time to time by males >13.7 m in length. The proportion of large males in the population rose to 2-3% in April. Males were observed to adopt a 'searching' strategy, moving between groups of females. Female pregnancy rates could drop substantially following either relative male depletion, or general reduction of the population. It is recommended that the 'harem' model of sperm whale social organization be replaced with one more consistent with these results. -from Author