Female chimpanzees employ babysitters to wean young faster

November 9, 2016, University of Toronto
Chimpanzees at play at Ngogo, Kibale National Park, Uganda. Here, infant Gus begs for honey from old male Bartok. Credit: Iulia Badescu

A babysitter can make a big difference in a parent's life. For wild chimps in Uganda, it may even mean that mothers can wean their infants faster, which can allow them to reproduce again more quickly.

A University of Toronto study looked at 42 pairs of chimpanzee mothers and infants at Ngogo, Kibale National Park, Uganda. They wanted to better understand the impact of "alloparenting" - or babysitting - when individuals other than the mother assisted with .

In a paper published in the Royal Society Open Science (RSOS), they describe looking at two particular aspects of care that these other individuals provided: infant handling, that is carrying and holding the infants, and natal attraction, the interest in infants demonstrated through behaviours like grooming and playing.

The researchers compared whether the extent of involvement of these individuals impacted the proportion of time that mothers spent foraging, the rates that infants nursed, and the contribution of milk to infants' diets.

"Infants who were held and carried more by babysitters, nursed less often and drank less milk," said Iulia Badescu, a PhD candidate in Evolutionary Anthropology at the University of Toronto, and lead author of the study. "This means that they were becoming more nutritionally independent compared to infants of the same age who were babysat less or not at all. They were going through the weaning process quicker, and would likely be done weaning at a younger age."

Babysitting may thus benefit mothers by enabling females to invest in their next offspring sooner through this accelerated weaning.

"But not all chimpanzee mothers relied on babysitters, and in fact, in other chimpanzee communities, babysitting may be a behaviour that rarely occurs. Our findings emphasize the significance of babysitting as a flexible component of female reproductive strategies in some species."

In a separate study, Badescu and her colleagues found that chimpanzee mothers let their "toddlers" nurse for comfort, even after lactation was over and they were receiving no milk.

"The young chimps were already weaned but continued to make contact with their mothers' nipple not for nutrition, but presumably for emotional purposes, when they needed to be comforted," said Badescu of the related study published in the American Journal of Physical Anthropology last month.

The researchers employed a novel method in both studies to arrive at their conclusions, analyzing fecal samples to determine what the contribution of maternal milk was to the diet of the chimpanzee infants. Until now, it has been very difficult to actually measure what animal infants eat in the wild, and Badescu and her colleagues are the first to use this non-invasive method with wild primates in large numbers.

"This novel method quantifies infant diets for us, so that we can know more precisely when weaning occurs for wild mammals, and also provides a biological way to determine if some are developing quicker than others" Badescu said.

Explore further: Baby monkeys grow faster to avoid being killed by adult males

More information: Alloparenting is associated with reduced maternal lactation effort and faster weaning in wild chimpanzees, Royal Society Open Science, rsos.royalsocietypublishing.or … /10.1098/rsos.160577

Related Stories

Mother-infant communication in chimpanzees

February 26, 2016

Animals other than humans learn how to communicate via the manual modality. Gestures are also important in the communication of great apes. Mothers of chimpanzees, for example, communicate with their infants mainly by tactile, ...

Recommended for you

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

TheGhostofOtto1923
1 / 5 (1) Nov 17, 2016
Traditional African proverb, "It takes a village to raise a child" and also something to do with a hillary book. No I'm not going to read it.

I wonder if the close interaction of pleistocene communities served as a check on individual character defects, and perhaps allowed these defects to flourish which only became a problem when emphasis shifted to isolated families with fewer children.

Children benefitted from the collective mental health of the village but began to suffer from the mental illness of individual mothers.

Monogamous relationships reduced competition for repro rights. Females of most species naturally want to choose the best possible donor for each successive child while males want to impregnate as many females as possible.

Both behaviors however are anathema to tribal stability and so members were selected for their ability to resist these tendencies; ie domesticated.

But marriage may not the best possible arrangement for children.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.