Chimpanzees start using a new tool-use gesture during an alpha male take over

June 28, 2018

"Leaf clipping is a special behaviour. It is a rare example of tool-use in a communicative context and has been proposed to be cultural, varying in its meaning in different social groups of chimpanzees", explains Ammie Kalan, the lead author of the study. Since leaf clipping is relatively rare, little is known about it. "Although only three adult males were observed to begin leaf clipping during our study period, by now we know that all of the mature males of the South group chimpanzees of the Taï forest do it", clarifies Kalan.

This is the first research examining how the leaf clip gesture, paired with a pant hoot vocalization in this group of chimpanzees, is associated with changes in the call's acoustics. In fact, it is the only study demonstrating this kind of complexity in chimpanzee communication. Using detailed acoustic analyses of pant hoot vocalizations and observations of leaf clipping behaviour, the authors show that pant hoots preceded by leaf clipping were more acoustically salient; they were longer, had more calls, more buttress drumming beats and lower frequencies. Moreover, during the alpha takeover, pant hoots also showed variation but the acoustic changes were different from those observed with leaf clipping.

"We cannot be sure of the exact mechanisms at play here since leaf clipping does not occur at the exact same time as the pant hoot but immediately before it", explains Kalan. "However, we think that leaf clipping probably re-appeared in this group due to the high arousal and aggression in the group during a time of peak male-male competition."

The authors also note in their article that males seemed socially frustrated and stressed during this period of hierarchy instability; therefore the leaf clipping may have helped to alleviate some of these effects. "Often, pant hoots by Taï chimpanzee males incorporate buttress drumming and are critical parts of the male display where vocal and physical prowess of individuals is demonstrated. Male displays are most likely important signals for regulating competition between males during periods of hierarchy instability; therefore, in hindsight, it is not surprising that leaf clipping re-emerged in this group at this time", describes Kalan.

Finally, the authors emphasize that it will be necessary to look at this phenomenon further in other chimpanzee groups and to examine the potential mechanisms that could explain these results. "This study adds to our understanding of the complex and multilevel nature of communication in wild chimpanzees, especially considering that combining signals, such as gestures and vocalizations, is a powerful way to gain communicative flexibility", says Kalan.
-end-


Max Planck Institute for Evolutionary Anthropology

Related Chimpanzees Articles from Brightsurf:

Like humans, aging wild chimpanzees value their more "positive" friendships most
Like humans, wild chimpanzees focus on fewer yet more meaningful friendships as they grow older, say researchers who studied male chimps over two decades.

Like humans, chimpanzees can suffer for life if orphaned before adulthood
A new study from the Tai Chimpanzee Project in Ivory Coast and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, shows that orphaned male chimpanzees are less competitive and have fewer offspring of their own than those who continue to live with their mothers.

For chimpanzees, salt and pepper hair not a marker of old age
Silver strands and graying hair is a sign of aging in humans, but things aren't so simple for our closest ape relatives--the chimpanzee.

In the wild, chimpanzees are more motivated to cooperate than bonobos
Scientists investigated cooperation dynamics in wild chimpanzees (Tai, Ivory Coast) and bonobos (LuiKotale, DCR) using a snake model.

A rare heart bone is discovered in chimpanzees
Experts from the University of Nottingham have discovered that some chimpanzees have a bone in their heart, which could be vital in managing their health and conservation.

In chimpanzees, females contribute to the protection of the territory
Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extensively studied several neighboring groups of western chimpanzees and their findings reveal that females and even the entire group may play a more important role in between-group competition than previously thought.

Cultural diversity in chimpanzees
Termite fishing by chimpanzees was thought to occur in only two forms with one or multiple tools, from either above-ground or underground termite nests.

Similar to humans, chimpanzees develop slowly
Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have systematically investigated developmental milestones in wild chimpanzees of the Taï National Park (Ivory Coast) and found that they develop slowly, requiring more than five years to reach key motor, communication and social milestones.

The genome of chimpanzees and gorillas could help to better understand human tumors
A new study by researchers from the Institute of Evolutionary Biology (IBE), a joint center of UPF and the Spanish National Research Council (CSIC), shows that, surprisingly, the distribution of mutations in human tumors is more similar to that of chimpanzees and gorillas than that of humans.

Crops provide chimpanzees with more energy than wild foods
A University of Kent study has found that cultivated foods offer chimpanzees in West Africa more energetic benefits than wild foods available in the region.

Read More: Chimpanzees News and Chimpanzees Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.