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 Gorilla
Island, Bristol Zoo, Bristol, England
Why do animals act the way they do? What
are the normal behaviors that a gorilla in
the wild would display? What does it mean
when gorillas, or other animals, in
captivity
demonstrate unusual behaviors?
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.
First, a few ‘behavior’ definitions and
explanations…
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.
Gorilla Palace
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.
So, how does this relate to nonhuman
primates, and gorillas in particular? The
U.S. Department of Agriculture (USDA)
established Animal
Welfare Regulations that authorized
programs to ensure the
psychological well-being of nonhuman
primates (USDA, 1985). Behavioral
abnormalities are indicative of sub-optimal
welfare in captive environments due to
negative internal functioning, impaired
mechanisms, denied species-specific
behaviors (Mason, 1991; Duncan and Fraser,
1997), as well as indicators of stress and
deteriorating homeostasis (Garner, 2005).
Confusing? I hope not! This topic is very
detailed and I am only skimming over the
definitions briefly to introduce these
ideas. Hopefully, you are developing a lot
of your own questions about these issues
that you can look into and research
yourself!
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).
Gorilla R&R
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.
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.
R/R, like other ABs, can be very harmful to
the individual. Some captive gorillas have
been observed to engage in R/R for over an
hour after they have been fed! That means
an hour of repetitive regurgitating and time
spent reingesting the regurgitated food.
Remember those criteria for psychological
well-being outlined earlier by the
USDA? R/R behavior contradicts nearly all
of them – it can lead to or indicate poor
physical health, it is not a
species-specific behavior, it could indicate
chronic distress, and it is not an
appropriate response to its surroundings.
R/R also takes time away from the gorilla
participating in appropriate
species-specific behaviors, like foraging,
socializing, and feeding to ingest mandatory
nutrients. Hill (2009) also found that
reingesting the regurgitated food is
physically harmful to the gorilla because
the regurgitated food is more acidic when it
comes back up than when it was first eaten.
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)
Regurgitation 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).
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