©iStock.com

Natural History
Jane Goodall
Life in the Wild
Life in Captivity
Life in a Laboratory

The common chimpanzee, Pan troglodytes, is the closest living relative of humans, Homo sapiens. Chimpanzees and human beings share many traits. For instance, chimpanzees can experience many of the same emotions and states as humans, such as pleasure, depression, anxiety, pain, distress, empathy and grief. In addition, chimpanzees are very social and highly intelligent. They can even be taught American Sign Language.

In the wild, chimpanzees range across equatorial Africa. They typically live in large social groups. Young chimpanzees live with family members for many years, learning the skills necessary for survival. They form life-long relationships and can suffer from depression when a loved one is lost. They communicate with a vast range of sounds as well as through body language. Chimpanzees make and use tools and can solve problems. Altruistic acts are not uncommon among chimps—particularly within families—but chimpanzees are also capable of being deceptive in order to gain access to something they want.

The average male chimpanzee is approximately four times stronger than the average human male. Unlike the cute and playful pranksters they depict in the entertainment world, chimpanzees do not willingly cooperate with their "trainers" and are typically subjected to physical abuse in order to make them perform. Chimps more than 5 years old become dangerous, and most at that age are "retired" to other uses, like research or breeding for entertainment purposes.

In the Beginning…

Chimpanzees were first thought of by non-Africans as "half-man, half-beast," with the hooves and tail of a horse. Stories brought back by sailors, who heard and believed tales told by the indigenous populations, helped fuel the myths. The first chimpanzee to be brought to Europe arrived in 1640. Over the next two centuries, chimpanzees were acquired by various European zoological gardens but seldom lived very long.  When, in 1859, Darwin published his theory of evolution, a new interest in animal behavior began, and the first attempt to study chimpanzees in the wild was subsequently undertaken.

One curious individual, R.L. Garner, enclosed himself in a large cage and spent months in the West African jungle observing chimpanzees. This attempt, however, is not recognized as contributing a great deal to our knowledge of chimpanzees.  In the early 1900s, an extensive study of captive chimpanzees was undertaken by psychologist Wolfgang Kohler on the Canary Islands. His book, "The Mentality of Apes," remains an important contribution to the literature on chimpanzees.

In 1925, another psychologist, an American named Robert Yerkes, purchased what he thought were two young chimpanzees, who would later become the nucleus of the Yerkes National Primate Research Center in Atlanta.  Until the 1940s, the Yerkes center primarily focused on the study of chimpanzee behavior. However, it was not until 1960 that chimpanzees would finally be studied comprehensively in the wild.

Enter Jane Goodall

©iStock.com

In 1960, a young English woman named Dr. Jane Goodall began a life-long study of chimpanzees in the wild, and much of what is known today about chimps in the wild is due to her work. Through years of living in close proximity to wild chimpanzees, Goodall was able to form relationships with dozens of animals and was accepted by their close-knit community. Virtually every aspect of chimpanzee life has been documented and filmed, demonstrating how alike they are to us.

Because of Goodall's work, animals who were once simply dismissed as amusing pranksters are now accepted and understood to be complex, intelligent beings.  Moreover, her studies of wild chimpanzees showed us healthy, intact communities of animals living in natural habitats, in stark contrast to the neurotic behavior we had observed in those chimpanzees who had been captured and forced to live in zoos, circuses, and research laboratories. 

Life in the Wild 

Chimpanzees spend almost 50 percent of their waking time feeding and around 13 percent moving from one location to another where food is available.  There are two peak times of day for feeding, one in the morning and one in the afternoon/evening. Approximately 48 percent of the food consumed is fruit, 25 percent is leaves and leaf buds, and 27 percent is seeds, blossoms, stems, bark, and resin. They also eat insects, caterpillars, honey, bird eggs, birds, and small mammals. Chimpanzees occasionally hunt, kill and eat larger animals such as bush pigs, bush fawns, and other primates such as baboons and colobus monkeys.

The adult male chimps studied by Goodall in the Gombe region of Tanzania weigh between 82 and 100 pounds, and adult females weigh between 71 and 82 pounds. Males are fully grown at the age of 17, and females are fully grown at age 19. Female chimpanzees experience menstruation, which begins around the age of 10 or 11. Female sexual maturity is reached between ages 12-14 years. Gestation averages around eight months.  Usually, a single birth occurs but twinning does happen, with triplets being more unusual. 

Infant chimpanzees are dependent on their mothers up to age 5 for milk and transportation. Older infants ride on the backs of their mothers when traveling any distance, but small infants must be carried by the mother the first year of life. Locomotion is generally accomplished on all fours, particularly when the group is traveling from one location to another. Bipedal movement is frequently used for shorter distances, and especially by adult males during threatening behavior toward a subordinate.

Chimpanzees are mostly diurnal and build sleeping nests in trees for the night. These nests are constructed of branches and leaves, and they're usually located where the evening meal is consumed. The nests may be used more than once if the family unit spends longer periods of time there. 

The social life of chimpanzees is complex, with individuals or smaller groups leaving and then rejoining the group after varying periods of time.  Males remain in their natal group for their entire lives, while females of reproductive age emigrate and take up residence in neighboring communities. Male chimpanzees form a dominance hierarchy, and often form coalitions of two to three males who co-rule the group. Females are not as social with other females as males are with males; however, a dominance structure does exist among them. 

Position within a chimpanzee community is sometimes challenged, especially amongst males, in striving for the lead position. Threat displays are used to assert and maintain dominance, and can involve charging, screaming, rock-throwing, and thrashing with a stick. In a more serious altercation, chimps will physically attack each other by biting, hitting, and throwing each other to the ground. Facial expressions are used extensively to communicate, and eye contact is also crucial to expressing dominance or submission.

Life in Captivity

Chimpanzees have been used in research in the United States since the 1920s. It began with the work of Yerkes, who established a laboratory at his rural home in Orange Park, Florida, with two chimpanzees that he purchased. Only years later was it discovered that the two animals were, in fact, one chimpanzee and one bonobo, (Pan paniscus), a smaller ape. 

	©iStock.com

Yerkes' observations of the two animals, based upon the mistaken assumption that they were the same species, pointed to differences between them based upon their sex. Despite this misguided start, Yerkes' work was critical to the emergence of primate studies in the United States. His operation moved to Emory University in Atlanta, where it became known as the Yerkes National Primate Research Center.  In the 1940s, the focus at the center shifted from the study of behavior to the study of infectious disease. Since then, the use of chimpanzees for this field of research has increased, especially in the areas of hepatitis and Human Immunodeficiency Virus (HIV).

In the 1950s, the U.S. Air Force created a research and breeding program with 65 wild-caught chimpanzees for use in the space program. Three chimpanzees—Ham, Enos and Minnie—were used to test space travel. Ham was launched into space three months before Alan Shepherd, the first human sent into space. Ten months after Ham's space travel, Enos was successfully sent to orbit the earth. Minnie was never actually launched into space.

Space research caused the chimpanzees pain and distress, and included procedures such as exposure to G forces, loss of consciousness in decompression chambers, spinning in giant centrifuges and the use of shock as punishment while training. After Ham and Enos were sent into space, the Air Force chimpanzees were reassigned to other projects, such as testing of seat belts. By the 1970s, the Air Force no longer used chimps but leased them out for biomedical research studies. The Air Force divested itself of its chimpanzee colony in 1998.

Behavioral research of chimpanzees, including both field studies and captive studies, has demonstrated time after time the chimpanzee's cognitive abilities. These include the use of tools (39 have been documented, such as the difficult task of using sticks or grass to lure termites out of termite mounds or using stones to crack nuts), numerical skills including counting abilities, and comprehension of American Sign Language and graphic symbols. 

In 1975, the Convention on International Trade in Endangered Species (CITES) was adopted, greatly restricting the importation of chimpanzees from the wild. As a result, captive breeding within the United States began, and has been federally funded since 1986. The chimpanzee is listed as "endangered" under the U.S. Endangered Species Act, but unlike any other species, it is listed as "threatened" in captivity. This "split-listing" status permits certain types of biomedical and invasive research when chimpanzees are bred in captivity.

During the 1980s, research using chimpanzees increased primarily due to the AIDS epidemic. Other areas of research have included malaria, gene therapy, respiratory viruses, and drug and vaccine testing. Experiments in these areas, such as studies of certain strains of HIV, can lead to severe appetite and weight loss, lethargy, diarrhea, severe illness, infections and/or death. Procedures such as major surgery, liver biopsies, blood sampling, and restraint cause pain and distress.

Life in a Laboratory

©iStock.com

In stark contrast to the rich, wild habitat where their senses, psyches, emotions, and social lives have evolved, chimpanzees used in invasive protocols are typically housed alone in steel cages whose only requirement (see Animal Welfare Act, below) is that the interior size be a minimum 5' x 5' x 7'.  This is roughly the size of the interior of an elevator and, though specified as a minimum, has often been the actual cage size used. 

This space may or may not have a perch for resting or sleeping. Some of these cages have a "squeeze back," a moveable interior wall that allows the animal to be pressed forward, enabling a technician, veterinarian or researcher to give an injection or conduct some other procedure without anesthetizing the chimp. Besides the pain and distress of the procedures themselves, individual housing can lead to profound depression, increased aggression, psychological withdrawal, and self-mutilation such as hair-plucking, physical wounding, rocking, and other psychotic-like behaviors. For more information, read  Psychological Effects of Laboratory Life on Chimpanzees

Given the potentially long life span of chimpanzees, the harm done by such housing is immeasurable. Research presuming to study the behavioral and social aspects of chimpanzees for the benefit of humans stands a great chance of being flawed. Extrapolation of research results from chimpanzees to humans is already problematic, both scientifically and ethically; the numerous stressors associated with laboratory conditions only further compromise the validity of these results.

Chimpanzees not being used in active research—which at any given time is the case for the majority of chimpanzees in labs—are typically housed in pairs or social groups. The physical environment for social housing can range greatly in size, depending on the number of animals, the institution itself, and the type of research for which they are being used. For more information about the lives of chimpanzee in laboratories, read Chimpanzees in Laboratories: A Day in the Life.

For more information about chimpanzee use in research, read Frequently Asked Questions about Chimpanzees in Research

Click here to read The HSUS's position on the use of great apes in biomedical research.