In my last blog, I introduced the western lowland gorilla and briefly discussed what their lives are like in the wild – how their environment, food, and behaviors differ from what we may see in captive populations. I’d like to now focus a little more on animal behavior as a function of living in captivity.
The normal behavior displayed by an organism (i.e. anything from an insect to a human) has a role in allowing a process called homeostasis to occur. This process enables the organism to control and alter its environment (Garner, 2005) by behaving in a way that allows it to maintain internal functioning and physiology. For example, in the wild a gorilla will forage and feed anywhere from 50% – 70% of the day to maintain appetitive, digestive, and physiological needs. However, captive surroundings may inhibit these normal behavioral reactions, possibly resulting in stress (Garner, 2005). Abnormal behaviors (I’ll call them ABs for short) may develop and indicate that an animal is unable to regulate its behavior to the captive environment (Garner, 2005). This can be harmful because it takes time away from healthy behavioral activities like caring for its offspring, socializing, and even physiological processes like healthy digestion can be disrupted. For instance, when an animal is housed in a captive environment, it may be unable to display species-specific behaviors, like foraging for 50% of the day (because food may be available only at certain times). Thus, it is possible that ABs may develop instead as a way to compensate for the inability to perform its normal behavior.
An example of a western lowland gorilla enclosure in a UK wildlife park. While it looks very different from a wild gorilla habitat, there are many factors to make this enclosure enriching for the animal. There are climbing robes, thick layers of substrate (hay) for a soft walking surface, ladders, bars, tubes, logs, and feeding puzzles. Despite an enriching captive enclosure, gorillas and other non-human primates can still develop abnormal behaviors.
Let’s bring it back to captive western lowland gorillas. If you recall from my first blog, these gorillas eat a lot of fruit, browses, bark, and they eat or actively search for food (forage) for at least 50% of their day! How could this be replicated in captive environments? It certainly would be very difficult – studies have shown that western lowland gorillas in the wild travel anywhere from 1.2 – 1.9 miles per day pursuing food and feeding opportunities. That would need to be a really large enclosure if it were a zoo or captive area and many institutions do not have the funding or space to provide the area needed. Rogers et al., 2004 reported that western lowland gorillas consumed an average of nearly 150 different food species. This is a significant variety of food, which varies drastically with the season. This can be difficult to represent in captive facilities depending on location, funding, and local weather. Studies have also shown that zoos are not providing enough of certain nutrients in the diets for captive primates (NRC, 2003). Just like you and me, lacking essential nutrients (protein, fiber, vitamins) or having too much of one kind (sugar, fat, cholesterol) can result in health problems. These are just a few examples of how life in captivity can be very different from the wild. It is not surprising that these differences can possibly lead to behavioral abnormalities in a captive animal.
We have to keep in mind that the occurrence of certain ABs are likely influenced by many factors (Lukas, 1999). Thus, presence in an animal’s behavioral repertoire may be indicative of inferior welfare in social, dietary, and/or environmental conditions (Lukas, 1999).
A particular AB observed in some captive gorillas is called Regurgitation and Reingestion (R/R), although other captive nonhuman primates display this AB as well. There are many other kinds of ABs that are displayed by captive gorillas, but I am going to focus on R/R. This is very common in captivity, with around 65% of all captive gorillas exhibiting this behavior. However, it has never been observed in wild conspecifics, which is why it is considered abnormal (Loeffler, 1982 as reviewed by Lukas, 1999; Akers and Schildkraut, 1985; Gould and Bres, 1986; Wiard, 1992). R/R is also known as an appetitive behavioral disorder because it is related to feeding activities. Its occurrence is a serious concern to the welfare and management of great apes in captivity.
This is a female gorilla exhibiting regurgitation and reingestion behavior. The food, which she had eaten for dinner, is voluntarily brought back up her esophagus and into her mouth, hands, or on the floor. She then eats the regurgitated matter over again (reingestion). It is not clearly understood how gorillas voluntarily control the regurgitation events or why they do it. It is different than vomiting because vomiting is the ejection of stomach contents, usually in a series of involuntary spasmic movements.
What can you do?
A lot of zoo visitors do not understand what is happening when they see a gorilla or other captive animal displaying R/R behavior. They tend to lose interest in the species or interpret them unfavorably. Visitors may think that this behavior is gross and this perception might be reflected back upon the captive animal. In turn, visitors may lose the desire to learn about gorillas, and cause a decrease in the number of people that become involved in conservation efforts.
Instead, try to understand why the captive animal you are viewing may be displaying an AB, like R/R. You can ask the animal’s caretakers or look around its living space and come up with some of your own hypotheses. You can ask questions like a) How was this individual raised? b) What kind of food is s/he eating? c) Is s/he showing any other ABs? d) Did something stressful happen right before s/he began showing a particular AB? e) What was the animal doing right before s/he engaged in the AB? f) What kind of enrichment items does the animal have available to him/her?
These are just some examples, but there are so many more questions you can ask! And spread the word – if you notice someone at a zoo or sanctuary teasing a captive animal that is displaying an AB, you can inform the caretakers and they can address the issue. This animal may be sick and it is important that we use our developing knowledge of ABs to help the captive animals experience a positive living environment that reflects their habitat and quality of life in the wild.
What does that mean?
- Captivity: Animals that live under human care.
- Homeostasis: The tendency toward a relatively stable state between related elements, especially as maintained by physiological (bodily) processes.
- Animal Welfare: The physical and psychological well-being of non-human animals.
- Psychological well-being: Encompasses several key criteria specific to non-human primates - a) the primate is in good physical health; b) it exhibits a considerable range of species-specific typical behaviors and does not display high levels of abnormal, stereotyped, or disorganized behavioral patterns; c) is not in a chronic state of distress; and d) it is capable of responding appropriately to environmental surroundings (Novak and Suomi, 1988).
- Rugurgitation and Reingestion (R/R): Backward movement of food up the esophagus and into the hands, floor, or mouth and the subsequent consumption of the regurgitated matter (Lukas et al., 1999).