In 2019, researchers sailed to a sprawling seamount off the coast of South Africa, and lowered hydrophones to the seafloor. They picked up all kinds of noises: waves, the crackling of the reef, dolphin clicks and whistles, and an assortment of humpback whale calls. Mixed in with the humpback sounds were noises reminiscent of gunshots. Right whales are known to make gunshot sounds, but none were around at the time of recording. So were these mysterious sounds coming from humpbacks? “We’ve never really heard about it being made by humpbacks or seen anything in the literature,” Erin Ross-Marsh, t…