Subtle variations in sperm whale calls suggest that individuals announce themselves with discrete personal identifiers. To put it another way, they might have names.

It’s long been known that sperm whales use click sequences, or codas, to communicate across miles of deep ocean. Scientists have now studied a particular coda made by sperm whales around the world. Called 5R, it’s composed of five consecutive clicks, and superficially appears to be identical in each whale. Analyzed closely, however, variations in click timing emerge. Each of the whales studied seems to have its own personal 5R riff and the differences were significant.

http://www.wired.com/wiredscience/2011/03/sperm-whale-names/#