With Valentine's Day right around the corner, we've been hearing an awful lot about love, romance, and couples. While it's sweet, the truth is that when it comes to monogamy, animals rarely participate. Over 90 percent of mammals have multiple mates and even those who form socially monogamous partnerships are often observed "cheating" on their partners. Although this behavior is common, some animals have earned a special reputation for their promiscuity. Read on to find out who are the biggest swingers of the animal world.