Geographical and Seasonal Distribution of Australian Pygmy Right Whales ( Caperea marginata ) Based on Passive Acoustics

Abstract

The pygmy right whale ( Caperea marginata ) is one of the least studied mysticete species. To shed light on its geographic and seasonal distribution, we compiled archival acoustic recordings from 26 sites across southern Australia and developed a deep‐learning detector for pygmy right whale “doublet” vocalizations. Seasonal patterns differed markedly between regions: On the southwestern shelf, detections consistently peaked between July and November (with an anomalous early season in March–June 2012), whereas southeastern waters exhibited more dispersed year‐round call presence, with pronounced peaks in July–October 2012, March, May–June, August, November–December 2015, June–November 2016, and February 2017. Co‐occurrence analysis of doublet and “spot” calls revealed synchronized presence/absence, supporting the hypothesis that both call types originate from the same species. Our findings underscore region‐specific habitat use and seasonal migration of pygmy right whales and highlight the value of automated acoustic techniques combined with ecological context for monitoring cryptic cetaceans in data‐limited environments.

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