An international research team, led by Hjalmar Kühl and Ammie Kalan of the Department of Primatology at the Max Planck Institute for Evolutionary Anthropology and the German Centre for Integrative Biodiversity Research, gathered a dataset on 31 chimpanzee behaviors across 144 social communities or groups that are located throughout the geographic range of chimpanzees. Part of the information gathered is based upon previous studies conducted, but they expanded their research and went to 46 locations over the last nine years.
The set of behaviors that were considered in this study that they conducted included the consumption of ants, termites, nuts, algae, and honey. They also included the use of tools for digging or hunting and the use of pools, stones, and caves among others.
The behaviors shown in a given situation was investigated concerning the measure of human impact. This measure formed multiple levels of human impact such as population density, river cover, roads and forest cover, all of which are indicators for the disturbance and the degree of land cover change that is found in the habitats of chimpanzees.
"The analysis revealed a strong and robust pattern: chimpanzees had reduced behavioral diversity at sites where human impact was high," explains Kalan, a researcher at the Max Planck Institute for Evolutionary Anthropology. "This pattern was consistent, independent of the grouping or categorization of behaviors. On average, chimpanzee behavioral diversity was reduced by 88 percent when human impact was highest compared to locations with the least human impact."
So, what can be the mechanism that is responsible for their loss of behavior?
Just like humans, population size plays a massive role in maintaining the cultural traits of the chimpanzees. Their reduced habitats and the depletion of their resources reduced their opportunities for social learning and prevent the transfer of their tradition from one generation to another. Climate change is also an important factor as it can influence the production of their food resources, and causing it to be unpredictable. The combination of these factors resulted in decreased behavioral and cultural diversity in chimpanzees.
"Our findings suggest that strategies for the conservation of biodiversity should be extended to include the protection of animal behavioral diversity as well," says Kühl, an ecologist at the iDiv research center and the Max Planck Institute for Evolutionary Anthropology. "Locations with exceptional sets of behaviors may be protected as 'Chimpanzee cultural heritage sites' and this concept can be extended to other species with high degree of cultural variability as well, including orangutans, capuchin monkeys or whales."
