Increasing evidence of humpback whale calving in the south-west of Western Australia

Abstract

An understanding of the spatial and temporal range of marine mammals, and identification of habitats that support critical behaviours is fundamental for effective species management and conservation. The humpback whale, while considered to be recovered within Australian waters, is subject to increasing levels of anthropogenic pressure across its migratory range. Increasing population size, in concert with long term climatic change, is likely to lead to intra and inter-species competition for food resources and habitat. Historically, humpback whales have been known to calf in the Kimberley region, with recent records of calving extending into the Pilbara as far south as Ningaloo Reef, off Exmouth Western Australia. This paper presents empirical evidence of significant numbers of humpback whale calves being born over 1500 km further south in Ngari Marine Park, southwest Western Australia, along their northern migratory route, including live sightings of neonates, deceased strandings of neonate calves and evidence of killer whale predation events. The presence of calving behaviour outside of known calving grounds presents challenges for species conservation and management with effective mitigation and management of anthropogenic pressures contingent on a contemporary understanding of species presence and behaviour. Further, there is considerable concern for the viability of calves this far south on their migratory route where water temperatures are cooler and sheltered areas for resting are more limited.