Spatiotemporal distribution of humpback whales off north-west Australia quantifying the Exmouth Gulf nursery area

Humpback whales (Megaptera novaeangliae) migrate from their Antarctic feeding grounds to their north-west Australian breeding grounds. North-west Australia has experienced rapid development of the mining and petroleum industry, and remains under increasing human pressure. The aim of this study was to examine the spatiotemporal distribution of humpback whales across the north-west: North West Cape, Pilbara and Exmouth Gulf. Aerial surveys (n = 184) were conducted from 2000 to 2010. After accounting for survey effort, kernel density estimation was used to assess the monthly distribution of whales. The largest density hotspot of whale groups was the centre to western edge of Exmouth Gulf. The highest encounter rate of mother–calf pairs was in October in Exmouth Gulf (0.0447 ± 0.0082 groups/km), which was significantly higher than in the North West Cape and Pilbara (0.0005 ± 0.0002 and 0.0011 ± 0.0005 groups/km, respectively). The comparison among the three regions confirms and quantifies Exmouth Gulf as an important nursery area for humpback whale mother–calf pairs. Nursery areas are important for lactating humpback whale mothers as they carry the highest energetic demands in the population. It is crucial that nursery areas remain relatively undisturbed from human pressures so mothers can rest to conserve energy and nurse their young.