Dialects in leaf-clipping and other leaf-modifying gestures between neighbouring communities of East African chimpanzees - Scientific Reports
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Dialects are a cultural property of animal communication previously described in the signals of several animal species. While dialects have predominantly been described in vocal signals, chimpanzee leaf-clipping and other ‘leaf-modifying’ gestures, used across chimpanzee and bonobo communities, have been suggested as a candidate for cultural variation in gestural communication. Here we combine direct observation with archaeological techniques to compare the form and use of leaf-modifying gestures in two neighbouring communities of East African chimpanzees. We found that while both communities used multiple forms, primarily within sexual solicitation, they showed a strong preference for a single, different gesture form. The observed variation in form preference between these neighbouring communities within the same context suggests that these differences are, at least in part, socially derived. Our results highlight an unexplored source of variation and flexibility in gestural communication, opening the door for future research to explore socially derived dialects in non-vocal communication.
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    2•1 year ago

    Summary created with Quivr/GPT-4

    User: What is this document about? Give me a detailed summary explaining the discoveries and observations in this document. Use plain English that is easy to understand and really highlight the potential benefits of the discoveries made.

    Assistant: This document is a research study on the communication methods of chimpanzees, specifically focusing on their use of leaf-modifying gestures. The researchers observed two communities of East African chimpanzees in the Budongo Forest Reserve, Uganda, and recorded their use of leaf-modifying gestures, which are brief but noticeable actions involving leaves.

    The study found that there are variations in the use of these gestures between the two communities, suggesting the existence of ‘dialects’ or cultural differences in chimpanzee communication. This is similar to how human languages and bird songs can vary based on geographical location and local ecology. The researchers also found some overlap in the use of these gestures between the two communities, which could be due to their shared habitat or cultural transmission between the groups.

    The researchers used statistical tests to compare the frequency and forms of leaf-modifying gestures between the two communities. They categorized the gestures into two forms: leaf-clip and leaf-pull/tear. They found that most of these gestures were performed by mature individuals in both communities.

    The study also discusses the challenges of observing these gestures, as they are visual signals that can’t be recorded when the chimpanzee is not fully visible. However, the researchers note that new tools in primate archaeology can help infer a behavior took place without directly observing them, by examining the material evidence left behind by the chimpanzees.

    The potential benefits of these discoveries are significant. Understanding the communication methods of chimpanzees can provide insights into their social structures, behaviors, and cultural variations. This can contribute to our knowledge of primate behavior and evolution, and potentially inform conservation efforts.

    User: What is a leaf clipping or leaf modifying gesture? I have no idea what they are, please give me any information you can on them, how they are used, in what contexts, etc.

    Assistant: Leaf-modifying gestures are a category of gestures used by great apes, particularly chimpanzees, in which individuals modify leaves and small leafy stems as an inherent part of the gesture action. This can be done through tearing, ripping, or removal of leaves or small leafy stems. Four forms of leaf-modifying gestures have been reported in great ape communication: leaf-clip, leaf-tear, leaf-pull, and leaf-drop.

    The term ‘leaf-clipping’ has been used to describe a behavior where a chimpanzee rips apart one or more leaves from the midrib and lamina using their mouth while holding the leaves in their hand. Other variants of this behavior include tearing of leaves using both hands instead of hand and mouth, and the tearing of leaves at different locations on the leaf.

    These gestures are used in various behavioral contexts, such as before buttress drumming or to solicit others for sex. However, the gestures are distinct from other leaf-modifying behavior not used during gestural communication, such as leaf-grooming or leaf-inspecting.

    It’s important to note that there is variation in the way these gestures are produced, and this variation doesn’t necessarily mean they represent distinct gesture ‘types’ or categories from the perspective of the chimpanzees using them. The gestures may represent a gradient with varying levels of visual and audible information.

    Recent studies suggest that chimpanzees show cultural variation in the frequency with which these behavioral forms are used. For example, neighboring communities in the Taï National Park, Ivory Coast, exhibited different preferences for hammer tools used for nut cracking. Similarly, different communities of chimpanzees may prefer different forms of leaf-modifying gestures.

    User: So, they modify or tear a leaf while another animal is watching them, and it is believed that the way in which they do this has a specific meaning?

    Assistant: Yes, it is correct to say that chimpanzees modify or tear leaves in the presence of other animals, often as a form of gestural communication. The manner in which they modify the leaves, such as leaf-clipping, leaf-tearing, leaf-pulling, or leaf-dropping, is believed to potentially carry specific meanings. However, the exact meanings and whether these gestures represent distinct categories or variations within a single category is still a subject of study.