Wild chimpanzee mother cares for disabled child

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Associate Professor Michio Nakamura

Over 23 months in the Mahale Mountains National Park, Tanzania, a research team from Kyoto University observed how a female chimpanzee cared for her disabled infant. This was the first time that such an infant was observed in the wild, and also the first report of a disabled infant surviving for nearly two years.

The infant showed striking similarities to characteristics seen in Down's syndrome. The mother -- an experienced 36 year old female -- cared for the child differently compared to how she had raised her other offspring, for instance by carrying it in one arm while walking. The infant's older sister also provided help in looking after the child. In addition, the team reports that other individuals did not express negative attitudes toward the disabled child.

The infant disappeared one month after the sister gave birth to her own child.

The researchers believe that the mother's "flexible" child rearing and extra help from the sister were instrumental in helping the infant survive in the wild.


(a) The mouth tends to be half open (age: 9 months)
(b) Abdominal hernia on the stomach (age: 11 months)
(c) The mother lays the baby on the ground when grooming (age: 6 months)
(d) There is a sixth finger on the left hand (hyperdactylia) (age: 10 months)
(e) The older sister provides help in babysitting (age: 10 months)
(f) Partial hair loss on the back (age: 10 months)

Research team

Takuya Matsumoto, Michio Nakamura, Noriko Itoh, Sana Inoue

Researcher's comments

It's been 50 years since research started in Mahale, but this was the first time that such a case was observed. We believe that this has important implications for understanding the evolution of a complex society, namely one that is capable of supporting vulnerable individuals. (Associate Professor Michio Nakamura)

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Paper Information

[DOI] http://dx.doi.org/10.1007/s10329-015-0499-6
[KURENAI Access URL] http://hdl.handle.net/2433/201516
Takuya Matsumoto, Noriko Itoh, Sana Inoue, Michio Nakamura
"An observation of a severely disabled infant chimpanzee in the wild and her interactions with her mother"
Primates , Published online: 09 November 2015

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