On the coast of Western Australia , a humpback whale is “pirouetting”, sweeping its pectoral fins through the water, its massive jaw hanging wide open. Surrounded by companions, the animal isn’t lunging for a meal: rather, it is putting on a mysterious behavioural display. This underwater ballet, captured on camera by an onlooker and shared online, is one of the clearest examples of a rarely documented phenomenon known as “gaping”. Whale-watchers witness a whale displaying gaping behaviour. As autumn chills Australia’s east coast, the ocean transforms into a bustling humpback highway . May marks the mammals’ annual migration from Antarctic waters to the warmer breeding grounds of Queensland and northern New South Wales – and for those with shoreline views, it heralds the start of whale-watching season. Scientists believe gaping may be a social display or a way for calves to stretch their mouths before feeding.…