( CNN ) -- It 's just days till Christmas , and many young girls around the world will be thrilled to find little dolls under the tree to play with . But there 's new evidence that it 's not only human girls who enjoy playing with imaginary babies -- young apes may be showing the same behavior . A research paper published Tuesday has found what its authors say is the first-ever evidence that young female chimpanzees in the wild `` play '' with sticks as if they are dolls . `` We find that juveniles tend to carry sticks in a manner suggestive of rudimentary doll play , '' they write in the current issue of Current Biology . `` And , as in children and captive monkeys , this behavior is more common in females than in males . '' The team of researchers watched and logged the Kanyawara group of chimpanzees in the Kibale National Park in Uganda for more than a decade . They were surprised to see young female chimpanzees carrying around sticks , apparently mimicking the way that mothers in the group cared for their own infants . The behavior would go on for up to hours at a time . `` The juveniles carried pieces of bark , small logs or woody vine , with their hand or mouth , underarm or , most commonly , tucked between the abdomen and thigh , '' they wrote . `` Individuals carried sticks for periods of one minute to more than four hours during which they rested , walked , climbed , slept and fed as usual . '' Co-authors Sonya Kahlenberg of Bates College and Richard Wrangham of Harvard University found that such behavior was witnessed only rarely among young male chimpanzees , pointing to the controversial idea that differences in play behavior even in other primate species may be gender-driven . Boy chimpanzees typically used sticks as weapons , shaking them to intimidate playmates . But just like human boys with `` action figures , '' young male chimpanzees were sometimes seen playing with dolls as well . Kahlenberg described one 4-year-old male named Kakama in an e-mail response : . `` He was observed to bring his stick into his nest and play the 'airplane game ' with it , that is , he laid on his back with his arms and legs extended upward and balanced the stick on his upturned palms and 'flew ' it from side to side . This behavior is performed by mother chimpanzees with their infants and , of course , human parents do it as well . Another interesting observation is that Kakama even constructed a separate nest for his stick . '' It could be some combination of nature and nurture , as monkeys and apes have been observed playing with toys and dolls in captivity before , with previous studies showing an affinity for females to take on mothering role-play . `` Sex differences in juvenile stick-carrying did not result from females observing their mothers carrying sticks , since mothers never carried sticks , '' the study found . `` Instead , youngsters apparently learned socially from each other . Such juvenile traditions have previously been described only in humans . '' So should this behavior in any way alter the way we perceive chimpanzees , and any affiliation with human behaviors ? `` Regarding how this study is related to the sex difference that we see in how human children play , it has at the very least contributed to the discussion of the factors underlying these differences , '' Kahlenberg answered . `` Our results suggest that part of the explanation may lie in innate differences between males and females . Specifically , there may be differences in how the sexes play that shape how they interact with toys , including which types they prefer . '' That finding would suggest there may be a genetic and gender-driven force behind the play . The behavior seemed to be a practice exercise for how to care for babies , with the chimpanzees often seen taking the sticks back to their nests and playing with them in the same way mothers did with real offspring . The authors say that the doll play may have evolved to help the animals learn how to be better mothers and caretakers .
Report in Current Biology : It is more common in females than in males . Young often carried sticks in a manner similar to mothers do for their young . The chimps typically carried sticks as weapons , but sometimes exhibited doll - play behavior . Research paper was based on more than a decade of chimps in Uganda .