Nature
A whole population of whales swapped their song for a stranger's tune in two years
Humpback whales off eastern Australia abandoned their traditional song and adopted, almost note for note, a completely different song sung by whales from the Indian Ocean population. Researchers tracked the switch after a handful of 'foreign' males turned up singing the new tune, and within about two years nearly every whale in the population had switched. It's one of the fastest cultural changes ever documented in a non-human animal.