Dwarf Minke Whale ( Balaenoptera acutorostrata ) Mother and Calf Ecology in East and Southern Australia

ABSTRACT

Knowledge of mother–calf pairs, migratory patterns, female reproductive cycles, and birth‐year calf development are all essential for understanding risks in these critical life stages and monitoring little‐known dwarf minke whale ( Balaenoptera acutorostrata ) populations. Rare great barrier reef (GBR) sightings of mother–calf pairs accumulated by the Minke Whale Project from 2003 to 2023 plus sporadic southeastern Australian sightings were analysed. Imagery was used to identify individual whales, and calf length and breathing rate data were collected. Mother–calf spatiotemporal distribution, calf development, and calving intervals of resighted females were analysed. From > 20 years accumulated data, 215 of 293 (73.4%) sightings were from the GBR austral winter aggregation area, and 76 (26.6%) along the southeastern coastline. Sightings shifted north until late May and south from August, with no spatial shifting over the June–July aggregation period. Combining calf length and breathing rate data, this suggests calving occurs in southern regions during the northbound migration, and a GBR calving ground is unlikely. Limited resightings of mother–calf pairs confirm some remain in the GBR for extended periods, and calf morphometric data suggests a doubling in length over the first year. Calving intervals of 1–3 years were recorded, using resighting histories of GBR females. This research highlights the need for investigating dwarf minke spatiotemporal patterns of migration, particularly of mothers with calves, to better inform population monitoring, risk management, and the development of predictive models.