A number of years ago scientists documented a strange cooperative hunting relationship among badgers and coyotes. While they are natural enemies -- coyotes sometimes eat badgers, it turns out they both eat squirrels, marmots and prairie dogs. Thus, rather than face each other down they, on occasion, cooperatively hunt together in order to take advantage of the particular skill set each animal possesses.
Badgers and Coyotes catch ground squirrels differently. Badgers usually dig them up, coyotes pounce on them or chase them. Ground squirrels often escape a digging badger by leaving their underground burrows and running away across the surface of the ground. These same ground squirrels escape coyotes by running into burrows and disappearing underground. A ground squirrel will theoretically have less chance to escape a badger and a coyote hunting together. If it runs away from the coyote by going underground into a burrow, the badger will dig it up. If it leaves a burrow to escape the badger, the coyote will run after it and catch it.
These cooperative relations are not short term -- out of 214 observed associations in one study, over half of them lasted more than an hour and 2 lasted for over five hours. A brief video on the phenomena is here.
This is just one of a wide range of phenomena discussed in The Unselfish Gene, an interesting article by Yochai Benkler author of the soon to be released The Penguin and the Leviathan: How Cooperation Triumphs over Self-Interest.