Species-specific beaked whale echolocation signals

TLDR

Beaked whales emit species‑specific frequency‑modulated upsweep pulses, whose variation is thought to arise from niche separation, anatomical limits, and prey‑size adaptations, with higher frequencies offering finer resolution but shorter detection ranges that may be offset by increased repetition rates. The study aims to use habitat modeling with acoustic detections to elucidate how ecological niches and prey influence species‑specific FM pulse types. The authors identified FM pulses from eight known beaked whale species and five additional distinct pulse types likely from separate species, with evidence that smaller whales produce higher‑frequency signals, suggesting a body‑length–frequency relationship.

Abstract

Beaked whale echolocation signals are mostly frequency-modulated (FM) upsweep pulses and appear to be species specific. Evolutionary processes of niche separation may have driven differentiation of beaked whale signals used for spatial orientation and foraging. FM pulses of eight species of beaked whales were identified, as well as five distinct pulse types of unknown species, but presumed to be from beaked whales. Current evidence suggests these five distinct but unidentified FM pulse types are also species-specific and are each produced by a separate species. There may be a relationship between adult body length and center frequency with smaller whales producing higher frequency signals. This could be due to anatomical and physiological restraints or it could be an evolutionary adaption for detection of smaller prey for smaller whales with higher resolution using higher frequencies. The disadvantage of higher frequencies is a shorter detection range. Whales echolocating with the highest frequencies, or broadband, likely lower source level signals also use a higher repetition rate, which might compensate for the shorter detection range. Habitat modeling with acoustic detections should give further insights into how niches and prey may have shaped species-specific FM pulse types.