A BBC natural history crew has filmed the "humpback whale heat run", where 15m long, 40 tonne male whales fight it out to mate with even larger females.
During the first complete sequence of this behaviour ever captured, the male humpbacks swim at high speed behind the female, violently jostling for access.
http://news.bbc.co.uk/earth/hi/earth_news/...000/8318182.stm