Calving intervals, longrange movements and site fidelity of southern right whales (Eubalaena australis) in southeastern Australia

Abstract

Southern right whales in south‐eastern Australia are endangered and vulnerable to impacts from human disturbance. Information on population demographics and movement data is needed to inform ongoing species management. While the number of whales observed using the south‐eastern Australian coastline is increasing, there has been no change over three decades in the annual abundance of cow‐calf pairs at Logans Beach in Warrnambool, Victoria, the only established calving ground in south‐east Australia. Knowledge of life history parameters of the south‐eastern Australian subpopulation is lacking. Here, we examine sightings and photo‐identification data from southern Australia to investigate calving intervals, long range movements and fidelity to the Logans Beach calving ground. Sightings data revealed at least 93 calves were born at Logans Beach between 1980 and 2018 (an average of 2.6 per year) with a mean calving interval of 3.5 ± 0.2 years (± SE, n = 34). Comparison between photo‐identification catalogues compiled for south‐eastern and south‐western Australia shows that southern right whales are wide ranging within southern Australian waters. Females can be sighted at locations as far apart as 3,800km across seasons with at least 7% of whales using both regions. We also provide the first report of an Australian southern right whale female belonging to one subpopulation relocating long‐term to a calving area in another. This work highlights knowledge gaps for the south‐east Australian subpopulation such as the proportion of female calves born at Logans Beach returning to their natal site and the degree of mixing between the two Australian subpopulations outside their wintering areas. Our work provides the first assessment of calving rates, movement and site fidelity within the south‐eastern Australian subpopulation, critical for understanding constraints to recovery and informing conservation management of southern right whales in Australia. Targeted, long‐term monitoring programs across south‐eastern Australia are needed to provide demographic information on which to base assessments of the impacts of anthropogenic threats such as noise disturbance, entanglement and vessel strike.