The evolution of stable social groups can be promoted by both indirect and direct fitness benefits. Sperm whales ( Physeter macrocephalus ) are highly social, with a hierarchical social structure based around core groups of adult females and subadults, a rare level of complexity among mammals. We combined long‐term satellite tracking (ranging from 11 to 607 days) of 51 individual sperm whales with genetic kinship analysis to a...

Humpback whales wintering in the Revillagigedo Archipelago, Mexico, have been considered a different subpopulation from those found off mainland Mexico and Baja California. The primary feeding grounds for Revillagigedo humpbacks remain unknown. In February 2003, we deployed 11 Argos satellite‐monitored radio tags to track movements and surfacings of humpback whales (five adults without calves, five mothers with calves, one cal...