Bisexual Walruses.

Male walruses don’t reach sexual maturity until they are four years old. During that time, they are most likely exclusively involved in same-sex relationships. The older males are typically bi-sexual, mating with females during breeding season and copulating with other males the rest of the year. Males rub their bodies together, embrace each other and even sleep together in water.

–From "Top ten gay animals" at LiveScience.com