Let's face it, most animals get around. Only about 5 percent of mammals are considered to be monogamous. What a biologist means by monogamy is not necessarily what a marriage counselor might assume. In the animal kingdom, what we think of as commitment-type monogamy should really be separated out into at least three types of bonds, explained Diane Witt, who leads the Neural Systems Cluster at the National Science Foundation, in a live chat last week. There is sexual fidelity, social attachment and parental behavior. Research in a number of animal species suggests that differences in neurochemicals and receptors might influence various degrees of these sorts of pairing.

For instance, birds are quite socially monogamous, with some 92 percent of species sticking with one mate for at least a mating season. But that does not mean that some of them are not getting a little extracurricular action. With the advent of genetic testing, scientists have been able to get the inside scoop on flings by testing parents and offspring. So even birds with a reputation of respectability were often caught straying from the nest.

Not all animals, however, have ended up with a scarlet letter from science. See which animals stay true to their true loves and how humans stack up against animal kingdom odds.

View slide show of 12 mostly monogamous animals.