Adult male Chacma baboons pose threats to the survival of the babies of their own species by killing up to 50 percent of the young. However, infanticide appears to be not just limited to these large monkeys that are primarily found in South Africa.
Killing babies of their own kind is also a behavior exhibited by a number of other animals including lions and lemur. In a bid to have a better understanding of infanticide among mammals, Dieter Lukas, from the University of Cambridge, and Elise Huchard, from the University of Montpellier, looked at observational studies involving 260 species of animals, 119 of which practice infanticide with the males observed killing the young not related to them.
The researchers also conducted a study on how infanticide has evolved over the past 160 million years and found that the common ancestor of the present day mammals did not kill their young. Infanticide is an evolved behavior that independently emerged in separate animal lineages.
Lukas and Huchard, however, observed that there are few things in common among the animal species that evolved infanticide. The females in these species often give birth year-round and not just once a year. Females also outnumber the males in animal groups.
The researchers explained that by killing the offspring of their competition, the males can fast-track the female back to full baby-making capacity. In short, infanticide is a sexual strategy.
"The study confirms that infanticide isn't some curious thing caused by humans encroaching on animal territory, it is a male tactic to improve their mating opportunities," said Kit Opie, from the University College London.
It also appears that the females of these species have come up with a strategy to prevent the males from killing their young and this involves mating with as many males as they can in a short time. This strategic promiscuity makes it difficult to discern the infant's paternity and the males stop killing the young if there is the possibility that the offspring is their own.
"Infanticide primarily evolves in social mammals in which reproduction is monopolized by a minority of males," the researchers wrote in their study, which was published in the journal Science on Nov. 14. "It has not promoted social counterstrategies such as female gregariousness, pair living, or changes in group size and sex ratio, but is successfully prevented by female sexual promiscuity, a paternity dilution strategy."
