Competing studies seek to offer explanation of animal monogamy WASHINGTON, July 30 (UPI) -- U.S. scientists have published competing theories for why some animals are monogamous and some are not: convenience or protecting offspring. The answers to one of nature's most vexing questions is a difficult one since scientists can't see hard evidence of when and how certain species developed monogamous behaviors. That leaves them to study current mating and rearing habits and use mathematical equations to extrapolate how and when they began. The two studies, one published in the journal Science and the other in Proceedings of the National Academy of Sciences, offer differing hypotheses. In Science, researchers suggest monogamy was an offshoot born of convenience for males mating with multiple females who lived great distances from one another. In the NAS study, scientists suggest males took a single female as a means to protect their offspring from competing males that might see it as a hurdle to mating with the female and try to kill the young animals, the Los Angeles Times reported Tuesday. A third leading theory is that males mated exclusively with one female to prevent infanticide. Birds are the animals most likely to live in monogamous relationships. Only 9 percent of mammals are monogamous. Among primates, the group that includes humans, 29 percent of species are monogamous.