How Scientists Habituate Chimps

Habituation is key to observing and researching primates in the wild. Former director of research, Mike Wilson, shares his thoughts based on his work for JGI at Gombe.

When I was 5 or 6 years old, I saw Dian Fossey on television, sitting in dense vegetation with a group of mountain gorillas. It amazed and delighted me that a person could sit so calmly with these magnificent, wild creatures. That image motivated me to become a primatologist.
 
How is it possible that gorillas and other wild animals can allow scientists to sit with them and follow them around, recording the details of their lives? The answer is “habituation.” It is a basic and important tool used for studying primates and other wild animals.
 
What is habituation?
The American Heritage® Stedman's Medical Dictionary defines “habituate” as “to accustom by frequent repetition or prolonged exposure.” It’s a technical word for a very common psychological process. When you first hear an unusual sound, say, like a car alarm down the street, you pay attention to it. But if the sound continues and nothing much happens, eventually you ignore it. Habituation is important for distinguishing changes in the environment and for differentiating between unimportant or harmless situations versus potentially dangerous ones. In animal behavior studies, habituation specifically refers to the process of getting animals used to people.
 
Why habituate primates?
Most wild animals fear people for good reason: humans are the most dangerous creatures on the planet. But there’s little we can learn about the behavior of wild animals if we only see them running away. In open country, you can sit in your car with your binoculars and watch animals from afar. In savanna parks, where animals have become habituated to cars, you can sit in a Land Rover and watch animals at closer quarters. But in forests, which is where most primates live, there are few roads, and trees block the view from the road anyway. So if you want to study primates, you must go to their “hang-outs.” Habituating them to your presence becomes necessary.
 
The primatologist is much like the cultural anthropologist: he or she seeks to be accepted into a foreign society, not as a member, but as an observer. Primatologists strive to be ignored while they observe and record events. Whether the study subjects are human or nonhuman primates, the new observer may experience a period of intense scrutiny, and may receive both threatening and friendly behavior before being able to work without altering subject behavior.
 
How does habituation work?
For habituation to work, animals need to see people regularly over a long period of time in non-threatening circumstances. For a long time, the habituator will get only sporadic glimpses through binoculars and will have long hours of seeing nothing at all. However, for those who are patient, have an interest in natural history, and enjoy activities like bird watching, identifying plants and insects, hiking and camping, habituating primates can be enjoyable and immensely rewarding.
 
You can speed the process up by providing food (“provisioning”). Wild animals are almost always looking for food, so if you provide food regularly, they quickly figure it out, and can rapidly overcome their fear of people to get that food reward.  Scientists used provisioning in a number of early studies, but the risks of doing so became apparent and the practice stopped at many research spots including Gombe National Park, site of Jane Goodall’s famous chimp research.
 
Are there any risks to habituation?
Habituation is not always a good thing for primates. If they lose their fear of researchers, they may also lose their fear of hunters and other predators, making them easy targets. Because primates reproduce slowly, the ilegal commercial hunting for meat is now a tremendous threat to many primate species.
 
Habituated primates can also be dangerous for people. When wild animals get used to eating garbage and picnic scraps that are left accessible by humans, they will lose their fear of humans and can become more aggressive. Vervet monkeys are known to steal food at regular picnic areas. Across Africa, many baboons and vervets have been shot as a result.
 
Intentionally using food to habituate primates can also pose a risk. Researchers have planted sugar cane to attract wild apes, such as chimpanzees in Mahale, Tanzania, and bonobos in Wamba, Democratic Republic of Congo. While provisioning makes habituation easier, it does create new problems in that it changes the behavior of the animals.  It is also worthy to note that because primates are our closest relatives, they are particularly susceptible to many of our diseases.
 
The general rule of thumb is that it is dangerous for both people and primates to get too close, as primates can feel threatened by the encroachment. At Gombe, park regulations stipulate that short-term visitors must keep 10 meters (33 feet) from primates, with researchers (who must undergo quarantine and health checks) being allowed somewhat closer.
 
Healthy Habituation
In primatology today, scientists seek to study animals without changing their behavior. This means habituation without provisioning. Not using food means habituation takes longer, and in some cases may be impossible, if for example the study groups are especially wide-ranging.
 
Primate habituation should only be attempted in areas where hunting is not a risk, and where good regulations are enforced, to ensure that people keep a good distance from primates. Any houses, offices, trash pits and other structures in areas with habituated primates must be secured to prevent primates from stealing food and other items.
 
How long does habituation take?
The general rule of thumb is that each individual primate needs about 100 hours to get used to people. In species that travel in cohesive troops, like baboons, every member of the group can see you every time you make contact, so the 100 hours go by fairly quickly, about 3 months. Chimpanzees take longer to habituate, because the entire social group rarely comes together. Individual chimpanzees often travel alone or in small subgroups, so it can take many years for every member of the group to become habituated. In forest sites, such as Kibale National Park in Uganda or Taï National Park in Côte d’Ivoire, habituation of chimpanzees without provisioning has taken 5 or 6 years. Habituation may take even longer in savanna sites such as Semliki, Uganda, where chimpanzees range over huge areas and only rarely encounter researchers.
 
How many groups are habituated at Gombe?
At Gombe, we have 2 habituated chimpanzee communities and 9 habituated baboon troops.
 
Jane Goodall habituated the Kasekela community of chimpanzees in the 1960s. Most of the chimpanzees in this community have spent their entire lives being followed by people, and do not see anything extraordinary about always having a few bipedal apes lurking nearby. Nonetheless, some individuals remain shy, especially females who have immigrated from other communities.
 
Efforts to habituate the Mitumba community, in the north of the park, began in the 1980s. Researchers set up a banana feeding station to attract the shy Mitumbans, then eventually began following them through the forest away from the feeding station. Feeding was reduced in 1996 and stopped altogether in 2000.
 
Researchers have not habituated the Kalande community, in the south of the park, though some attempts were made in the 1970s and 1980s. Because the south of the park is drier and more open, the southern chimpanzees have to range further for food, and have been more difficult to find. Moreover, because habituation may increase susceptibility to hunting, which has been a greater threat in the south of the park, habituation is not currently recommended for this community. However, since 1999, researchers have monitored this community at a distance, collecting fecal samples for genetic analysis and spotting individuals through binoculars, in order to estimate and keep track of their population size.
 
What is it like to habituate?
My first job as a primatologist was habituating baboons in Kenya, at the Mpala Research Camp. I worked with a Kenyan university graduate named Irungu. For the first weeks of the study, we drove and walked around Mpala ranch to find and choose a suitable study group. We spent many hours walking through dense thickets of “wait-a-bit” thorn (named because it grabs onto your clothes, demanding that you wait a bit before moving on), following the alarm barks of baboons who had disappeared from view. We chose a troop that slept each night on the rocks of a certain cliff, slumbering on either side of the little waterfall that tumbled down the cliff’s face.
 
Each morning before dawn, we drove as close as we could, then parked the car and walked to the cliff. From the top, we had beautiful views of the sun rising over Mount Kenya, with the Aberdare Mountains just visible to the southeast. By mid-day the baboons moved off into the bush and we went back to camp for lunch. We returned in the afternoon to wait for the baboons as they came back to their cliff. Eventually, after several months of this, we were able to follow the baboons for as long as we wanted. They sat and played comfortably within 10 meters of us. Gradually attaining they trust of these primates is one of the most satisfying things I have done.
 
--Mike Wilson, former director of field research at Gombe Stream Research Centre
 
 
 

Photos, top to bottom: Mike Nichols, Michael Neugebauer, JGI/J. Conciatore

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