Humpbacks are a friendly species that interact with other cetacean species such as bottlenose dolphins. Right whales interact with humpbacks. These behaviors have been recorded in all oceans. Records of humpback and southern right whales demonstrating what were interpreted to be mating behaviors have been documented off the Mozambique and Brazilian coasts. Humpback whales appear in mixed groups with other species, such as the blue, fin, minke, gray and sperm whales. Interaction with gray, fin, and right whales have been observed. Teams of researchers observed a male humpback whale singing an unknown type of song and approaching a fin whale at Rarotonga in 2014. One individual was observed playing with a bottlenose dolphin in Hawaiian waters. Recently, incidents of humpback whales protecting other species of animals such as seals and other whales from killer whales has been documented and filmed. Studies of such incidents indicate that the phenomenon is species-wide and global, with incidents being recorded at various locations across the world. In September 2017 in Rarotonga, the Cook Islands, two adult humpback whales were observed protecting snorkeler and whale biologist Nan Hauser from a 4. 5 m (15 ft) tiger shark, with one whale pushing the woman away from the shark while the other used its tail to block the predator's advances. This may be the first recorded incidence of humpback whales acting protective over a human.