Each community of chimpanzees occupies a large range. Each day, chimpanzees must travel to different locations within their territory in order to access the food resources they need. We can explore this behavior by asking a few basic questions. First, how do chimpanzees move through their environment? When you imagine chimpanzees moving through the forest, what do you see? Swinging from branch to branch. Chimps do use suspensory locomotion or swinging from their arms but only over short distances. More frequently, they climb through trees and walk along branches on all four legs, we call this arboreal quadrupedalism. Arboreal means in the trees. Quadrupedal means on all fours. But when they're covering long distances, they typically move down to the ground and walk. Humans walk on two legs, we call this being bipedal. Unlike us, chimpanzees walk quadrupedally on the ground. Like gorillas, they use a form of knuckle-walking. Look at the position of this chimpanzee's hands. Notice that her palm is not resting flat on the ground. Instead, she straightens her wrist and rest her weight on the backs of her middle knuckles. Scientists think that this position allows them to walk on the ground while accommodating the long, flexible fingers, they use to grasp tree branches when they climb. That's how they travel. Another question we might want to ask is how far they travel. Biologists have studied this question in all kinds of animals from bees to sea turtles to migrating birds. In chimpanzees, the answer is, well, it depends, on the characteristic of an individual chimpanzee, the characteristics of a given group, the season, and so on. In short, it varies a lot. When I was working in Gombe, I experienced the full range of that variation. This is a map showing real data of chimpanzees movements over two days. The numbers you see represent the GPS points I collected. On the day represented by the yellow line, I followed a large group of chimps on an all day journey across several valleys and ridge tops, a distance of around two point three kilometers and a lot of elevation. They hardly stopped for more than 20 or 30 minutes at a time. Another day, I sat under the same tree for hours as three females fed on the nice young leaves growing there. They came down a couple of times to groom and nap and ended up spending the night in a different tree just a few meters away. This day is represented by the short red line about 350 meters. Interestingly, I was following the same young female, Yamaha, on both of these days. You can see how much variation there is in daily path length, the distance traveled in one day. On average, in chimpanzees, this is about two point five kilometers or approximately one point six miles but it varies. Male chimpanzees tend to travel further and faster than females, more like three kilometers a day. Females travel more slowly and cover less ground around one point five kilometers a day. This is probably due to the fact that they have infants to carry and juvenile offspring, who need to be able to keep up. All chimpanzees change their daily habits in response to food availability, which changes over the course of the year. When there is a lot of fruit available within a small area, they don't need to travel very far to get enough to eat. But, if the trees bearing ripe fruit are few and far between, daily path length increases. Here's a chimp feeding on flowers instead of fruit in a dry season. He's traveled to the far edge of the community range high up in the ridge tops to find this resource. All of this is pointing us towards the most important question, why do chimpanzees travel? By now, you should have a pretty good idea. They primarily travel to find food. But, that's not the only reason, they also travel to patrol their territory, marking their boundary and attacking any strange chimpanzees that they find near the borders. They also need to travel to find mates. Because of the fluid social system, they can travel alone or in small groups. When females are ready to mate, they may need to travel to find males, or they may need to make more of an effort to keep up with a larger group.