Humans and chimps have different foraging patterns in the rainforest
A team of researchers from the Max Planck Institute for Evolutionary Anthropology set out to compare the spatial movement patterns of human foragers and chimpanzees in similar rainforest environments.
The Mbendjele BaYaka people are constantly changing camps and have a large lifetime range of about 800 square meters, while chimpanzees live in a much smaller area and spend most of their adult lives within the same home range.
The study was focused on the direction and speed of five Mbendjele BaYaka women from the Republic of Congo and five female chimpanzees from Taï forest as they ventured away from established trails on their daily quest for food.
The researchers found that both the Mbendjele BaYaka people and Taï chimpanzees had similarly high levels of linearity when they traveled toward locations that were out of sight. On the other hand, humans and chimpanzees showed clear differences in their movement as their surroundings and group sizes shifted.
The Mbendjele BaYaka traveled with higher linearity in familiar areas compared to less familiar areas. This pattern was reversed in Taï chimpanzees, who moved with higher linearity and speed in less familiar areas.
“One possible explanation of these differences can be their different ranging style,” said study lead author Haneul Jang. “The Mbendjele BaYaka people stay in several seasonal camps in their lifetime range, and walk 90 percent of their travel distance on human-made trails during their foraging trips in the forest. They may therefore have less experience in less familiar off-trail areas. Hence, when the Mbendjele BaYaka people forage in these areas, their travel linearity decreases due to their searching effort.”
“Since chimpanzee groups can be highly hostile towards each other, they might need to travel more efficiently and faster in less familiar areas, where they are more likely to encounter other chimpanzee groups.”
Travel linearity was found to increase among the Mbendjele BaYaka people when they traveled in larger groups, yet not among the chimps.
“When I followed the chimpanzees, I often saw them wait for each other and have apparent disagreements about where to go,” explained study supervisor Karline Janmaat. “With more individuals joining the group, disagreement seemed to increase. It is therefore perhaps not surprising that when group size increased, their travel became less linear.”
“For the Mbendjele BaYaka people we found the opposite pattern. This can have many reasons, but I like to think that it is because humans can discuss, evaluate and eventually agree about where the best food sources are, by using language, and that this helped them to travel more efficiently.”
According to the researchers, the study is the first necessary step needed to compare long-range spatial movement patterns of human and chimpanzee populations in their natural habitats.
“Our study provides insights into how two closely related species living in similar environments can differ in their spatial movement patterns, which possibly results from their different ranging styles,” said Jang. “We hope our study can contribute to expanding comparative research on spatial movement patterns to a wide range of primate species and populations, including humans, in natural environments.”
The study is published in the journal Scientific Reports.
Image Credit: Karline Janmaat