Humpback whales come to the assistance of other species by harassing the killer whales that are attacking those animals.

Robert Pitman at the Southwest Fisheries Science Center in La Jolla, California, and his colleagues reviewed reports of 115 interactions between humpback whales (Megaptera novaeangliae) and killer whales (Orcinus orca). In at least 31 cases, humpbacks approached and 'mobbed' killers as the killers attacked or fed — mostly on sea lions, seals and other whale species.

The authors suggest that the humpbacks responded to the calls of the attacking killers. They add that humpbacks do not seem to benefit from helping other animals, so this may be a case of interspecies altruism.

Marine Mammal Sci. http://doi.org/bm58 (2016)