Meet the Chimpanzees

Text by Michio Nakamura
Photographs by Luca De Santis

Chimpanzee research at Mahale was started in 1965. The one who started the research there was Toshisada Nishida.
He was, at the time, just a graduate student studying at Kyoto University, Japan. Since then, the research project has been continued seamlessly by many researchers for more than 50 years. It is not so common that a research project on a single mammalian species is continued at one place that long. From early on, the Japanese researchers had proposed to make Mahale as a protected area. Thus it eventually became a national park of Tanzania in 1985 with efforts by Japanese researchers. The financial support was given from the Japan International Cooperation Agency and it is a rare example that a national park was established through overseas aid by a Japanese governmental organization.
The Mahale Mountains National Park is located on the eastern shore of the Lake Tanganyika at the western side of Tanzania covering the area of about 1,600 square kilometers.

The Mahale Mountains chain runs from north-west to south-east with the highest peak, Mt. Nkungwe, being 2,462 m above sea level.

This mountain chain keeps the moist from the lake and in the wet season it rains heavily on the western side of the mountains. The mountains gather the rain water which flows down to the lake as many small streams. As such, a rich forest, called the Kasoje Forest, is developed between the lake and the Mahale Mountains. This forest is the home for the M group chimpanzees that is the subject of ongoing research and tourism at Mahale.
Mahale is also a home for various other animals. On trees of the Kasoje Forest, one would easily see small monkeys with clown-like gaily faces: the red-tailed monkeys. Red colobus monkeys, yellow baboons, several kinds of squirrels, warthogs, vervet monkeys, and the Nile monitor lizards can also be seen frequently near the research camp.
On the rather dim observation trails, one would often see a blue duiker, a small antelope that stands motionless fluttering only its small tail. At a certain distance, it suddenly skirls and runs into bush.
Leopards, porcupines, pangolins, aardvarks, bushpigs, and hyenas are also inhabitants of this forest and although you may not directly see them because of their nocturnal nature, you will find their feces on the observation trail. In the lake and river mouth, hippos, buffalos, and otters are also present.
When darkness covers the entire forest, you will hear the loud voices of greater galagos. You will also hear insects, frogs, nightjars, as well as the sounds of footsteps of nocturnal animals wandering about.
Leopards, porcupines, pangolins, aardvarks, bushpigs, and hyenas are also inhabitants of this forest

and although you may not directly see them because of their nocturnal nature, you will find their feces on the observation trail. In the lake and river mouth, hippos, buffalos, and otters are also present. When darkness covers the entire forest, you will hear the loud voices of greater galagos. You will also hear insects, frogs, nightjars, as well as the sounds of footsteps of nocturnal animals wandering about. Magnificent to hear may be the deep bass roar of the leopard known as “sawing sound.” The night at Mahale is also a busy quarter for wildlife.
As it is well known, we humans belong to the order Primates (an order including lemurs, monkeys, and apes). Therefore, studying various species of primates is essential for understanding what we are and how we evolved. The chimpanzee is, among several hundreds of species of primates, the closest sister species to humans. Some scholars even argue that due to its genetic closeness to humans, the chimpanzee should be included in our own genus, Homo.
Chimpanzee males in the wild weigh around 35 to 50 kg (some are over 60 kg in zoos) and females are about 10% smaller. If they stand bipedal, they are as high as 130 cm, much smaller than an average human female. This is because they have much shorter hind legs than we do, but instead they have longer hands. Chimpanzees are much stouter-built than we are. Especially, chimpanzee males are muscular and much stronger than human males. They especially look large when they erect their body hair. This piloerection may have the same mechanism as our gooseflesh when we get excited or feel tense. The difference is that we have very poor body hairs so that only pores of skin are visible as gooseflesh when we erect our hair.

Important foods for chimpanzees are ripe wild fruits. However, they also eat other parts of plants such as leaves, piths, flowers, or resins.

Mahale chimpanzees are known to utilize more than 400 items from more than 200 species of plants. This number is still increasing as research goes on.
Fruits usually have their seasons. That means chimpanzees’ important food habitat changes depending on seasons. What they eat are mostly “eatable” also to humans. Some fruits are good tasted and even sought for by local people. Some are too sour or too rough for humans but are sweet at the same time.
Mahale chimpanzees also eat some agricultural species such as lemons, guavas, and mangoes that are once cultivated by the local people but abandoned after Mahale became a national park and now have gone wild. However, strangely, chimpanzees in Mahale never utilize oil palm fruits that are high in calorie and eaten quite frequently by chimpanzees in Gombe which is also in Tanzania. This difference is not due to availability because we often see fruiting oil palms in the Kasoje Forest.

When chimpanzees find ripe fruits in the forest, they may emit a grunting vocalization. The local assistants call this vocalization

“a voice of delight.”

Once an alpha male, Fanana, tended to emit this sound often while climbing a fruiting tree and his grunting sometimes even became a cry.
Chimpanzees’ lips stretch very well and they often put many fruits in between teeth and lips and compress the mass of fruits to squeeze juice. After squeezing, they spit out the leftover fiber ball, called a “wadge.” Many wild fruits are tightly adhered to their seeds and cannot easily be removed. In such a case, chimpanzees swallow the whole fruits together with the seeds. You will often see many seeds are included intact in their feces. Such seeds are known to germinate better than seeds naturally fallen on the ground because the surface of seeds are moderately softened while going through the gut of a chimpanzee. The seeds in the feces are also an important source to know the foods of chimpanzees in a particular season.
Plants are their main foods but chimpanzees are not vegetarians. They also eat social insects such as ants and they love mammal meat very much. Chimpanzees at Mahale use tool to “fish” for arboreal Camponotus ants. The major mammalian prey is the red colobus monkey. When they hunt colobus monkeys, they get very excited, and when succeeded, noisy uproar of “carnival” continues sometimes for hours.

Many primate species such as most monkey species form a stable group, often called a “troop.” A troop is usually a compact group and you may visually confirm its members as they often are in close vicinity.

On the other hand, in a chimpanzee social group, its members are not always physically together. It may depend on the season, but usually an observer will see only a few to a dozen of chimpanzees moving together at a time. Such small temporal group is called a “party” (or “subgroup”) whose size and composition are not constant and always subject to change. For example, a chimpanzee A may be observed walking alone, or together with B, C, and D, but later on, he may be observed with B and E, and so on. A chimpanzee will meet and part with any chimpanzees in a group.
With such a fluid characteristics, western researchers first thought that chimpanzees did not have a stable social group except for enduring mother and offspring pairs. They thought that chimpanzees had a loose “community” in which any chimpanzees might meet and part without any boundary.

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Read the full story in Issue N.1 of Cartography