The extremely violent behavior of baboons that includes the killing of infants and attack on pregnant females to force miscarriages for early sex with those females has been unveiled in a new study.
This extreme case of domestic violence and homicide by baboons stands out for the involvement of feticides even though infanticide has not been uncommon among many animals, including lions.
The study is published in Proceedings of the Royal Society B after an extended monitoring of wild baboons at Amboseli in Kenya for almost four decades.
According to researchers, the killing of infants and destruction of the fetus are being used by aggressive male baboons as a means to bring back the females into reproductive readiness and cut the male's waiting time for mating.
Normally, pregnant and nursing females will not oblige for sex at least for a year when they are gestating or lactating.
The domestic violence escalates when aggressive male baboons join new groups where fertile females are scarce, noted first author Matthew Zipple, who is a graduate student in professor Susan Alberts's lab at Duke University.
The study points out that such violent baboons are in a minority who attack females and infants to facilitate speedy sex.
But this is the first time a stark behavior of attacking mothers to force abortions has been noticed, asserts the study.
Alberts, chair of evolutionary anthropology at Duke, commented that records of many animals including baboons, lions, dolphins and rodents have examples of infanticide. But feticide has been very uncommon.
The study also mentioned deaths of a quarter of pregnant or lactating baboons and their kids who are attacked by violent males.
Despite the casualties, scientists say the rogue males are still gaining. This is because female baboons who survive such attacks do mate with the violent male.
"By killing an infant, an infanticidal male causes the infant's mother to return to a reproductive state sooner than she otherwise would by eliminating a period of continued lactation during which she would not be cycling," the authors wrote.
The study said a feticidal male comes out a winner as he gets away with the waiting period caused by pregnancy and lactation.
According to the research, during the period between 1978 and 2015, the baboon population around Amboseli National Park in Kenya had reported 2 percent infant deaths and 6 percent miscarriages attributed to violence by migrant male baboons.
The death rates escalated more than three times in the absence of cycling females.
"In situations where males have few opportunities, they resort to violence to achieve what's necessary to survive and reproduce," said Zipple.
The mysterious jump in infant deaths and crashed pregnancies after the arrival of new males in a social group also showed that many 1- and 2-year-olds were spared. That showed an intentional targeting of pregnant females and nursing infants by the violent male baboons.
Male Goal Met
According to the study, the crude behavior of rogue baboons is still hitting their goals as mothers who lose babies no longer gestate or feed become pregnant again within 41 days.
According to the researchers, fertile females become acute during times of food scarcity as females take 15 percent more time for births. This abnormal waiting time provokes sex-hungry baboons to violence for meeting their goals.
"It's not just who they are, it's the circumstances they find themselves in that makes the difference," Zipple added.