SYDNEY, Aug. 13 (Xinhua) -- Australian researchers have found that playtime between baleen whales and dolphins is often a mutual activity, with many encounters involving "cooperative and reciprocal" social play.
Researchers analyzed 199 documented encounters involving 19 species, captured on videos or in photographs by the public, tourism operators and scientists across 17 locations worldwide, according to a statement released Tuesday by Australia's Griffith University.
The university's Whales & Climate Program lead, Olaf Meynecke, said a quarter of these interactions can be defined as a mutual interaction, with humpback whales (classified as baleen whales) responding positively toward dolphins in about one-third of cases.
"The humpback whales were rolling from side to side, undertaking belly presentation and other behaviors that are associated with courtship or friendly socializing," said Meynecke, the lead author of the study published in online journal Discover Animals.
The researchers observed that whales typically approached dolphins slowly with their heads and rostrums, with most interactions showing no avoidance. They were especially interested in recording whale reactions as dolphins are often being described as harassing whales.
The study found that the most common interaction was dolphins swimming near a whale's rostrum, much like bow riding, a behavior that may help dolphins travel more efficiently and, at times, serve as a form of one sided play.
Footage from underwater camera tags on humpback whales even showed bottlenose dolphins following humpbacks not only on the surface but also to the ocean floor for apparent social play.
The findings highlight marine mammals' complex social structures, and interspecies interactions in ocean ecosystems. ■
