A humpback calf photographed off Hervey Bay in Queensland last month carried fresh, broad cuts across its back, wounds that naturalists say were almost certainly caused by a boat's propeller. On a whale-watching tour that day, senior naturalist Isabel Taylor noticed the mother and calf hanging back from other whales that were breaching and slapping the water in front of delighted tourists. "The mood on the boat changed a bit," she recalls, once the slash marks came into view. That calf is far from alone.

Images gathered by WWF Australia and shared with The Guardian document a pattern repeating along the entire east coast, from a humpback near Sydney's Bondi Beach with exposed red flesh where a propeller blade appears to have struck repeatedly, to a female known to researchers as "bladerunner," whose back and tail still bear a deep, distinctive scar pattern believed to date back more than twenty years. Experts argue these are not isolated accidents but symptoms of a deeper imbalance: a whale population that has rebounded dramatically since commercial whaling was banned is now funnelled through coastal waters crowded with recreational and commercial vessels. Dr Raphael Mayaud, a marine ecologist at Griffith University who advises the International Whaling Commission on vessel strikes, says the images capture something statistics alone cannot. "These images really bring home the physical and direct impact we're having on these animals, especially on animals that size," he says.

Researchers including Rebecca Dunlop at the University of Queensland are now examining whether migration corridors and seasonal boating restrictions, already used in parts of North America, could reduce collisions along Australia's coast. The irony is stark: a conservation success story, decades in the making, is now generating a new kind of casualty.