The New York Times, 1992
Researchers who have spent thousands of hours observing the behavior of bottlenose dolphins off the coast of Australia have discovered that the males form social alliances with one another that are far more sophisticated and devious than any seen in animals apart from human beings. They have found that one team of dolphins will recruit the help of another team of males to gang up against a third group, a sort of multi-tiered battleplan that scientists said requires considerable mental calculus to work out.
https://www.nytimes.com/1992/02/18/science/dolphin-courtship-brutal-cunning-and-complex.html
https://www.nytimes.com/1992/02/18/science/dolphin-courtship-brutal-cunning-and-complex.html