A team of researchers has found that wild chimpanzees share their grooming habits with their mothers. Young chimpanzees learn skills from their mothers that translate to adult behaviors, including tool use and grooming techniques. The findings may help scientists better understand primate social behaviors. The details are in a paper that was just published in the journal Current Biology.
Mother chimpanzees (Pan troglodytes) care for their offspring for the first few years of life—about four to six years. They are dedicated caretakers and teach their young to find food, use tools, and engage in proper social interactions. Grooming is an especially important social behavior that also encourages good health.
Researchers from Harvard University studied groups of wild chimpanzees across Africa. They analyzed data from years of research from different populations. During the first 12 years of life, younger chimpanzees only groom their mothers. The research team investigated whether or not this changed the specific grooming behaviors the young chimps would later use in other social groups. There are many subtle variations in grooming behaviors and they can change between populations. One method is more obvious, however, and is called “palm-to-palm clasping”, a special form of what the authors refer to as high-arm grooming. During palm-to-palm clasping, the chimpanzee pair clasps hands while continuing to groom with their other arms. Scientists aren’t sure what this behavior means but it may encourage bonding or be some kind of communication signal. Palm-to-palm clasping is common in some chimpanzee populations but rare in others.
The research team found that the offspring of mothers who used the palm-to-palm clasping method of grooming were much more likely to stick with that particular grooming technique. In other words, young chimpanzees mimicked their mothers’ grooming style and continued using the same methods for the rest of their lifespan. One chimpanzee continued to use palm-to-palm clasping decades after his mother had passed away. The team found that the only factor that resulted in this type of grouping was maternal—chimpanzee grooming behavior was not affected by status, friendship, sex, or age.
The findings provide new insights into chimpanzee grooming behaviors and the skills passed down to offspring by their mothers. It appears that grooming style is learned from the mother and isn’t affected by any other factors. Scientists may be able to use this information to better understand primate learning.
Wrangham et al. Distribution of a Chimpanzee Social Custom Is Explained by Matrilineal Relationship Rather Than Conformity. Current Biology (2016).