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Chimpanzees Without Mothers Are More Aggressive

By Russell Tenofsky

Photo of a mother chimpanzee and her baby contemplating an object in her hand.A new study demonstrates that chimpanzees who grow up without a mother possess less social skills and exhibit more aggressive behavior than those who have mothers to care for them.

Scientists from the Comparative Cognitive Anthropology Research Group at the Max Planck Institute for Psycholinguistics studied the behavior of eight orphan chimpanzees against nine mother-raised chimpanzees.

The non-invasive study, conducted at Chimfunshi Wildlife Orphanage Trust in Zambia, found that motherless chimpanzees displayed more aggressive play behavior and a lower level of social awareness.

“Orphaned chimpanzees had more difficulties to successfully coordinate their social play interactions,” said head researcher Edwin van Leeuwen.

Humans raised the orphan chimpanzees at Chimfunshi until they reached the age of one or two years old, and then humans transitioned the chimpanzees into a group with other juvenile orphans.

Motherless chimpanzees displayed more aggressive play behavior and a lower level of social awareness.“The chimps in the study were between four and nine years old, so they have kind of been raising each other,” van Leeuwen said.

The scientists found that the orphans’ play sessions were shorter and more aggressive than their mother-reared counterparts.

“Although the orphaned chimps were motivated to play, it seems that they were less able to coordinate their play bouts and prevent them from resulting in aggression,” van Leeuwen said.

The researchers concluded that, just like in humans, mothers play a key role in passing on social skills and conduct.

“Since social play comprises a complex context in which signals about intentions need to be communicated, it seems that orphaned chimpanzees have missed out on valuable lessons from their mothers,” van Leeuwen said.

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