Abstract

In sperm whales, mature males are generally solitary and migrate long distances from high to low latitudes, while females and immatures form social units in subtropical and tropical waters. To study intraspecific and spatial variation in habitat use, we described four behaviors and we used two acoustic parameters: the Inter-Pulse Interval, which can be used to determine the size, age and/or sex of sperm whales, and the Inter-Click Interval of the regular clicks emitted during echolocation. Habitat was characterized by bathymetry, distance from shore and slope of the seabed. During 24 ship surveys we identified 19 aggregations and 73 individuals. The social structure was consistent with the literature, with aggregations composed of females and/or juveniles, immatures and sometimes mature males. Spatial distribution according to topography remained constant for all types of aggregations. However, habitat use varied with bathymetry and the presence of immatures, revealing the existence of specific areas for hunting and socialization, suggesting a trade-off between hunting and parental care in sperm whales. Although the social structure changed during the study period, the topographic distribution remained stable between January and June. This study highlights the influence of bathymetry on the social, spatial and behavioral dynamics of sperm whales.