When he visited Sri Lanka - one of the best places in the world to see blue whales - this was not the picture that photographer Tony Wu had in mind. Floating inert in the water, its body broken by a huge impact, this blue whale was almost certainly the victim of a ship-strike. Marine biologist Asha de Vos says that a few carcasses are discovered every year, but that exactly how many of these ocean giants are being killed is unclear. "The southern coast of Sri Lanka is home to one of the busiest shipping lanes in the world and it overlaps with areas of high blue-whale activity, so there is definitely cause for concern," she told BBC Wildlife. Get your copy of the latest BBC Wildlife magazine now!