Demographic Seasonality of Sperm Whale Presence in the Central Gulf of Alaska and the Aleutian Islands

Sperm whales are a sexually dimorphic, cosmopolitan species, with a stratified distribution. Generally, males grow larger and travel to higher latitudes, while mature females and immature whales form social units thought to be more common in tropical and temperate regions. Little is known about their migration, especially by males for mating. This study detected presence of sperm whales echolocation clicks and the spatiotemporal distribution of sexes at four sites in the central Gulf of Alaska and two along the Bering Sea Aleutian Islands,by using click characteristics as a proxy to estimate acoustic total body length and as an indicator for sex. Sperm whales were detected at all sites, including continental slope, deep abyssal, and seamount habitats. Some recording sites showed seasonal patterns potentially linked to the demographic composition of the population, especially males moving between temperate and high latitude regions. We also found females frequenting sites in these high-latitude habitats where they’ve been rarely documented since whaling. Our analysis improves understanding of the spatiotemporal distribution and population structure of sperm whales which is essential for efficiently estimating densities to inform appropriate management and conservation measures.