Chimpanzee

Chimpanzees are one of the five species of great apes, along with humans, bonobos, gorillas, and orangutans. They share some basic similarities with the other great apes such as dental structure, lack of a tail, opposable thumbs, and a large brain cavity. Chimpanzees are “knuckle-walkers” with arms that are 1.5 times longer than their legs. They can get as tall as 5.5 feet. Males weigh 90-120 pounds and are usually larger than females who weigh between 70-100 pounds.

Chimpanzees are covered in black fur except for their palms, ears, faces, and soles of the feet which are bare. As they age, the hair on their face will lighten and turn gray.

Chimpanzees have the widest range of any great ape, excluding humans. They are found as far west as Guinea and Senegal and as far east as South Sudan, Uganda, and Tanzania. However, they are not consistently found throughout this range and there are many isolated populations. They are mostly restricted to tropical rainforests and dorset-savanna mosaic environments. They can also be found in mountainous forests as far up as 2,750 m above sea level. Though less common, there are some populations known to inhabit savannas.

These apes are omnivores and feed opportunistically on a wide variety of food. Most of their diet consists of fruit and young leaves, which they spend most of their day foraging for. During the long dry seasons, they expand their diet to include things such as buds and blossoms, stems, honey, bark, seeds, and resin. Animal prey makes up only about 5% of their diet. They mostly prey on ants and termites, but will occasionally hunt down larger game such as monkeys, pigs, and antelope. Hunting is mainly done cooperatively between males, though sharing food is uncommon otherwise.

Chimpanzees are one of the few mammals that manufacture and use tools. They use twigs and vines and poke them into termite nest holes, then nibble on all the termites that cover the stick. Some populations chew leaves to make them more absorbent, dip them in water, and then drink the water off of them. There are other tools that vary from population to population, like cultural differences. West African chimps use wood and stone tools as hammers to open nuts.

Chimps have highly complex social structures with communities of anywhere from 15 to 120 individuals. These communities lack a definite leader and are usually split into a number of subgroups which are temporary and change in composition within a matter of hours or days (‘fission-fusion' groups). These groups are very male-bonded. Males almost never leave the community in which they were born and form tight-knit bonds with other males in the group. Tension is routinely expressed between males in small disputes for dominance. Males will form coalitions with other males and spend a lot of time grooming each other. Females on the other hand often travel either alone or with offspring. They are not closely bonded with any particular male outside of mating. Opposite sexes only occasionally groom each other; very rarely will two adult females groom each other. All females are considered subordinate towards all males. Since chimps are a patriarchal species, females are the ones that depart the groups they are born into while males stay with their family groups.

Each community of chimp has a defined territory that they patrol. They are very territorial and do not tolerate other groups they come across. Males may travel up to 3 miles a day, while females stay closer to core areas and only travel up to 2 miles.

Chimpanzees experience menstrual cycles, similar to humans, that typically last 36 days. Each cycle consists of a 6-day fertility window during which her genitals and surrounding skin will swell and turn pink or red. This swelling is known as tumescence. Females and males will mate with multiple partners, though dominant males sometimes try to prevent other males from mating with certain females. Sometimes a male, usually lower ranking, will discreetly take a female away from the main group for a period of time to ensure that no one other than him mates with her. Females can experience hundreds of matings during their tumescence period. The number of matings likely contributes to paternal confusion, which avoids potential infanticide.

Chimpanzee pregnancy lasts 7-8 months, after which females give birth to a 4 pound infant that clings to their mother’s stomach. As they get older they change to a more piggy-back style of transportation. Chimpanzees are weaned by 4 to 5 years old but do not reach maturity until they are 10 years old.

Chimpanzees are listed as Endangered on the IUCN Red List. Although there may be as many as 300,000 chimps in the wild, chimp populations have been reduced and fragmented by human encroachment into their habitats. As a result, their population trend is steadily decreasing. In addition, hunting by people for bushmeat or commercial exportation (for the pet trade and scientific research) has led to them being placed on Appendix II of CITES. They are also listed as Class A under the African Convention on the Conservation of Nature and Natural Resources, and considered endangered by the U.S. Fish and Wildlife Service. The most endangered of the chimp subspecies is P. t. ellioti, the Nigeria-Cameroon chimpanzee, which has fewer than 6,000-9,000 individuals in the wild.

• Sick chimpanzees appear to self-medicate in the wild. They will chew and swallow certain bitter tasting plants with anti-parasitic qualities when they have stomach ailments. Other leaves with high bioactive compounds are swallowed whole.
• There are only two animals in the world that have been observed invading the territories of enemies, with the apparent intent of harming or killing those encountered. This behavior is unique to humans (Homo sapiens) and chimps (Pan troglodytes). Most other territoriality in animals is non-violent and aversive.
• The species name troglodytes is a complete misnomer. This word means one who crawls into holes or caves, which chimps are not known to do.
• Humans and chimps share 98.7% of their genetic makeup. Our two species diverged somewhere between 7 and 13 million years ago.

The Oakland Zoo is home to a troop of six chimpanzees. Abbey, Amy, Caramia, and Andi are our four females, and Eddie and Berny are our two males. Our oldest chimp is Abbey, who came to live with us in 1987 when she was just 4 years old. In 1995, she had her daughter Amy. You can tell Abbey apart by her giant floppy ears and by the motherly role she plays. Abbey is very protective of not just her daughter, but Caramia as well. When Caramia first arrived at the zoo in 1996, she was only one year old. Caramia and Abbey bonded, and this bond stays strong to this day. If Abbey sees Caramia or Amy in distress, she will come running to help. These close female relationships are incredibly rare in the wild, but we see them a lot more in managed care.

Caramia has the most gray hair out of any of the chimps. You can also easily tell her apart because she only has one eye. Caramia is the type of chimp who knows exactly what she wants and how to ask for it. She has learned to clap at the keepers to get her attention and will clap at them and gesture to the misters to ask if they can be turned on.

Amy is our youngest chimp, but is still almost 30 years old. She is usually found with stuffed animals or in a nest of blankets. She is very independent and methodical in her planning. When the chimps get new enrichment, she gathers all her favorite enrichment in one spot to play with at once, instead of engaging with each item one at a time like the other chimps. When the misters turn on, she builds a nest of blankets so she can sit near them without getting wet.

Andi is the largest female of the troop. She frequently acts as the peacemaker of the group and is the first to help a chimp in distress. If keepers ever accidentally leave a key or a tool in the exhibit, Andi is always the first to find it and bring it back to the keepers so she can trade it for a treat.

Our two male chimps, Eddie and Berny, have a very close relationship. They are brothers who came to live with us in 2010. Eddie is the older of the two and was born in 1990, Berny is younger and was born in 1993. Eddie and Berny spend every evening grooming each other before dinner. Eddie is the alpha of the group and very respected by the other members. Berny on the other hand loves to stir the pot and annoy the others into chasing him around.

While Abbey and Amy were both born at AZA-accredited institutions, the other chimps have unfortunately come from less appropriate backgrounds. Caramia and Andi both previously lived at a non-invasive cognitive research facility where they were used as subjects. Berny and Eddie came from private owners that trained chimpanzees for the entertainment industry. Thankfully, Caramia, Andi, Berny, and Eddie were all rehomed to the Oakland Zoo, where we are better equipped to help them live a more natural and species-appropriate lifestyle.

Oakland Zoo is partnered with Kibale Fuel Wood Project which works to protect the Kibale National Park in Uganda. It has one of the densest populations of chimpanzees. The project assists families in using sustainable stoves to lessen deforestation, plants trees in the community, and does outreach and education. The Oakland Zoo sells "Beads for Chimps," beads and jewelry made by women living near the Kibale National Park. Oakland Zoo also partners with the Budongo Snare Removal Project, spearheaded by the Jane Goodall Institute to remove bushmeat snares from the forests where chimpanzees live. These snares loop around a limb and as the chimpanzee tries to get free, it tightens. Many chimpanzees, even if they are rescued, permanently injure or lose a limb from this trauma.

• Purchase Kibale Beads which sends money directly back into conservation in Uganda's Kibale National Park, through the Kibale Fuel Wood Project and the Budongo Snare Removal Project.
• Educate your friends and family about the illegal pet trade. Exotic, wild animals like chimpanzees do not make good pets and when they are poached from the wild, it is harmful for the individual, the ecosystem, and that local economy.
• See how we are taking action for chimpanzees here.