You might have romantic ideas about monogamy in the animal kingdom, but the truth is that only about 5 percent of species are together forever ... and forever is relative, because while they may be socially entwined with one other animal, the advent of genetic testing has taught us that they aren't entirely faithful sexually [source: Harmon].
But don't throw away your promise ring yet. Several animal species have been shown to naturally stick with one partner, with both parents taking care to raise and protect the kiddos, too. And although they might not be the most elegant example to point to during a wedding toast, prairie voles don't just mate for life but also groom each other and share a parental role. Studies found that even after a mate died, fewer than 20 percent found another mate [source: Harmon]. Sandhill cranes also mate for life, and messing around (or, as researchers call it, "extra-pair copulation") is so rare that a paper was written about an instance it was discovered, in 2006 [source: Hayes].
But monogamy isn't strictly for male and female pairs. Let's take a look at some animals that have what many think of as a "less traditional" partnership.