Orangutans named Hellen and Lucy watch researchers from a higher canopy.
Image: Takumi Tsutaya
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How do you determine how many months or years animal mothers nurse their babies? If you’re not in a rush and can observe this dynamic, you could supposedly stick around to see when the baby, mother, or both decide that they’re done. However, that could take years. A team of researchers investigating breastfeeding in orangutans recently opted for a different, perhaps surprising strategy—searching for particular proteins in poop.
In a preliminary study published in the journal Communications Biology, researchers searched for milk‑specific proteins in the feces of wild Bornean orangutans (Pongo pygmaeus) living in the Danum Valley Conservation Area, in the Malaysian part of the island of Borneo. These proteins prove that he or she is continuing to drink breast milk.The practice of recognizing particular proteins in feces is called fecal proteomics and it can help scientists better understand what animals are consuming.
“Orangutans have a slow life history with one of the longest interbirth intervals and the lowest reported infant mortality rates among primates or even mammals,” the team wrote in the study. “Breastfeeding is a key factor in their life history because it possibly promotes offspring health and increases maternal interbirth intervals.”
The team gathered fecal samples for over two and a half years, and found milk‑specific proteins in all the 20 samples from orangutans less than six and a half years old. This indicates that the young great apes were continuing to breastfeed until they were at least that age.
According to the team, these results are “consistent with the behavioral evidence as having one of the longest breastfeeding periods in mammals.”
What’s more, “milk intake was significantly correlated with higher levels of biological defense and probiotic bacterial proteins.”
In other words, the more milk a young orangutan drinks, the more probiotic intestinal bacteria it has and the sturdier its biological protections are. Such consistent and enduring breastfeeding probably helps the very high survival of orangutan babies and plays a role in their slow reproductive approach.
Unfortunately, Bornean orangutans are critically endangered, and the paper highlights why their populations don’t rebound quickly after a decrease. Safeguarding what’s left of their rainforest habitats is crucial.
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