Young male chimpanzees play more with objects, but do not become better tool users

http://www.eurekalert.org/pub_releases/2015-10/uoc-ymc100615.php

Public Release: 7-Oct-2015
Young male chimpanzees play more with objects, but do not become better tool users
University of Cambridge

New research shows a difference between the sexes in immature chimpanzees when it comes to preparing for adulthood by practising object manipulation -- considered 'preparation' for tool use in later life.

Researchers studying the difference in tool use between our closest living relatives, chimpanzees and bonobos, found that immature bonobos have low rates of object manipulation, in keeping with previous work showing bonobos use few tools and none in foraging.

Chimpanzees, however, are the most diverse tool-users among non-human primates, and the researchers found high rates of a wide range of object manipulation among the young chimpanzees they studied.

While in adult wild chimpanzees it is females that are more avid and competent tool users, in juvenile chimpanzees the researchers conversely found it was the young males that spent more time manipulating objects, seemingly in preparation for adult tool use.

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The sex bias for object manipulation the researchers found in juvenile chimpanzees is also found in human children. "The finding that in immature chimpanzees, like humans, object-oriented play is biased towards males may reflect a shared evolutionary history for this trait dating back to our last common ancestor," write the researchers from Cambridge, Zurich and Kyoto, who studied communities of wild chimpanzees and bonobos in Uganda and Congo for several months, cataloguing not just all tool use, but all object manipulation.

Immature females, on the other hand, showed lower rates of object manipulation, especially in play, but displayed a much greater diversity of manipulation types than males -- such as biting, breaking or carrying objects - rather than the play-based repetition seen in the object manipulation of immature males.

This seems to prepare the females better for future tool use. In an earlier study at Gombe (Tanzania), immature female chimpanzees were also observed to pay closer attention to their mothers using tools and became proficient tool users at an earlier age than males.

"Immature females seem to focus their attention on relevant tool use related tasks and thus learn quicker, whereas males seem to do more undirected exploration in play," write the researchers.

They say they believe the findings show that not all object manipulation in juvenile chimpanzees is preparation for tool use, and the different types of object manipulation need to be considered.

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"We suggest that the observed male bias in young chimpanzees may reflect motor skill practice for male-specific behaviours, such as dominance displays, rather than for tool use skills. It seems that not all object manipulation in immatures prepares for subsistence tool use. It is important to take the types of manipulation into consideration."

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