Actually, one other animal does:

The Bonobo; a relative of the chimpanzees.

When startled, or when finding a new place to settle for the day, the apes will gather in various groups for a gigantic orgy, swapping between same and opposite sex partners. They've been known to have sex dozens of times a day. For reference, I learned this in one of my anthropology classes in college.

[Linked Image]

[Linked Image from nodiatis.com]