Spatiotemporal distribution and population structure of sperm whales in the Eastern North Pacific

Abstract

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. Here, we outline an approach to detect presence of sperm whales echolocation clicks and the spatiotemporal distribution of sexes at 12 sites along the eastern North Pacific 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 the high-latitude habitats of the Gulf of Alaska and the Bering Sea Aleutian Islands, where they have been rarely documented since whaling. Our analysis improves the 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.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. Here, we outline an approach to detect presence of sperm whales echolocation clicks and the spatiotemporal distribution of sexes at 12 sites along the eastern North Pacific 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 the high-latitude habitats of the Gulf of Alaska and the B...