- A team of Japanese scientists have observed a mother chimpanzee taking care of her severely disabled baby in Mahale Mountains National Park in Tanzania.
- Nicknamed XT11, the disabled baby had abnormalities similar to those reported for a captive chimpanzee with Down-like syndrome, study reports.
- XT11 survived till she was nearly two years old, largely due to her mother’s care, the authors believe.
In Mahale Mountains National Park in Tanzania, a team of Japanese scientists observed a mother chimpanzee taking care of her severely disabled baby in the wild. This is the first detailed report of its kind, which looks at how a wild female chimpanzee responds to her disabled infant, researchers write in a recent paper published in the journal Primates.
Nicknamed XT11 by the researchers, the disabled baby was born to 36 years old Christina (nicknamed XT) in January 2011.
XT11 had numerous disabilities similar to those reported for a captive chimpanzee with Down-like syndrome. Researchers observed that her eyes looked empty and her mouth was often half open. She had a lump on her belly, which the team speculates could be due to abdominal hernia. She also had an extra finger on her left hand, and a bald patch on her back.
Behaviorally, XT11 was less active than typical infants of her age, the authors write. While healthy infants can sit up by six months, the team reports that XT11 could do so only after her twentieth month. The researchers also never observed XT11 walking or feeding on plants on her own. She remained dependent on her mother’s milk for much longer than chimps of her age typically are.
(10 months). e) XP (elder sister) holds XT11. f) Bald patch along the spinal cord (10 months); XT11 is held by XP upside-down. Image from Matsumoto et al, 2015.
Given these severe abnormalities, XT11 managed to survive until she was nearly two years old. This was largely due to her mother’s care, the authors believe.
XT11’s mother, XT, would carry her all day long, both while walking and while climbing trees, although it disturbed her own feeding.
“XT had to carry XT11 ventrally all the time, support her with a hand and walk tripedally, support her posture on trees, place her on her breast before suckling, and put her on the ground while grooming,” the authors write. “Without this kind of unusual and flexible maternal care, XT11 might not have survived for her entire 23 months in the wild.”
Sometimes, XT11’s elder sister, XP, stepped in to help by handling, carrying, grooming and playing with XT11. But XP stopped once she had her own children.
Moreover, chimpanzees usually allow non-relatives to care for their babies. However, XT did not allow non-relatives to take care of XT11.
“As there was no evidence that other individuals showed any aversion to or fear of the disabled infant, XT’s intolerance might have been due to understanding that her infant required unusual extra care and that letting others carry the infant was unsafe,” the authors write.
XT11 died in December 2012. While the cause of her death is unknown, the researchers speculate that one reason could be her poor diet.
Citation:
- Matsumoto T, Itoh N, Inoue S, Nakamura M 2015. An observation of a severely disabled infant chimpanzee in the wild and her interactions with her mother. Primates DOI 10.1007/s10329-015-0499-6
