This chapter
discusses the stereotypic behavior present in captive animals, mainly polar
bears. It defines stereotypic behavior,
its possible causes and methods of behavior manipulation. It also describes the things that these
animals do when bored and its effect on their life. Finally, it evaluates the mentioned methods
and indicates whether the polar bears in which these methods were used actually
improved their lifestyle.
What is Stereotypic Behavior?
Stereotypic behavior has been defined as a repetitive,
invariant behavior pattern with no obvious goal or function. A wide
range of animals, from canaries to polar bears to humans can exhibit
stereotypes. Stereotypic behavior is an abnormal behavior frequently seen in
laboratory primates. It is considered an indication of poor psychological
well-being in these animals. As it is seen in captive animals but not in wild
animals, attention has been focused on the situations in which this behavior
develops. (Philbin)
In the search for causes, the
emphasis historically has been placed on an animal's environment. It has been
believed that stereotypic behaviors will develop in a deficient environment!.
Several aspects of the captive environment of captive animals have been
investigated. These include cage size, housing type (individual vs. pairing or
groups), stress, and lack of environmental complexity.
Use of such small cages has
long been implicated as a cause of stereotypic behavior. The belief is that
wild animals confined in small cages will develop abnormal stereotyped
behavior? (Broom, Mendl and Zanella, 1995). The main aim of specification of minimum
cage sizes per body weight of animal was to promote more species-specific
behavior (including the vertical flight reaction) and to reduce abnormal
behaviors.
Stress is another factor of
concern. It has been suggested that the stress of life in a cage might
contribute to the development of abnormal behaviors. The inability of the
animal to escape from these experiences might lead to adoption of stereotyped
behaviors as a means of coping with an aversive environment. Some studies have
indicated that stereotypic behavior produces a 'trance-like' state (Stevenson,1983) and is linked to
reduced awareness of the environment
associate stereotypes in human children with analgesia. Finally, one
final aspect of the environment that has been considered to cause stereotypic
behavior is boredom. (Philbin)
A
THEORY OF ANIMAL BOREDOM
Generally
speaking, animals housed in a barren environment show an overall decrease in
interaction with the environment. This comes to expression in a variety of
symptoms (Wemelsfelder, 1990). The animals lie down and sleep more, and spend
significantly more time sitting. On the other hand, they over- react to novel
and/or unexpected events with fearful and aggressive responses. Furthermore,
the animals may develop stereotyped patterns of behavior. Such patterns consist
of high repetitive and uniform sequences of behavior which seem to be of no
direct functional value to the animal. Examples are bar-biting in tethered
sows, stereotyped pacing shown by zoo animals such as polar bears and wolves,
and various locomotory stereotypes in laboratory primates. Sometimes such
behavior can be damaging to other animals; licking and nibbling tails and ears
of offspring may for example induce cannibalism in rats and mice.
As time of confinement
proceeds, such patterns tend to become increasingly directed towards the animal's
own body or products thereof. Primates may spend long periods of time
masturbating, rocking their own body, or eating and regurgitating their own
feces. Rats may chase their own tail, tethered sows may show long bouts of
chewing air, with no other apparent effect than producing large amounts of
saliva. Such tendencies may eventually develop into various forms of compulsive
self-mutilation. Laboratory monkeys gnaw at their own limbs or genitals, while
parrots will pull out their feathers until completely naked. In summary, the
overall decrease in interaction shown by captive animals comes to expression in
decrease in behavioral variability and an increase in self directed behaviors
(Dantzer, 1986).
The Interpretation of Abnormal Behavior
Behavioral scientists
mostly refer to the behavior patterns described in the previous paragraph as
"abnormal," because these patterns, by and large, do not occur in the
wild. Moreover, they bear a strong resemblance to behavior pathologies in human
beings. It is generally accepted that in human beings, abnormal behavior
may be a sign of depression, or other forms of subjective suffering. In
animals, however, it is by no means regarded as self-evident that abnormal
behavior involves suffering.
Moreover, Wemelsfelder proposes
that in long term captivity, animal behavior gradually loses its active and
flexible character. In the development of abnormal behavior such as
stereotypes, we see behavior becomes increasingly rigid, and loses its
flexibility. The self-directedness of the behavior shows animals close
themselves off from their environment, rather than interact with it. One may
object and hold that such a process can still be regarded as an adaptation to a
barren environment. The non-adaptive character of abnormal behavior comes,
however, best to expression in the response to novel stimuli or a novel
environment.
Various studies indicate that
animals who have developed stereotyped behavior patterns no longer actively
interact with novel stimuli (Wood-Gush, Stolba and Miller, 1983). Most
poignantly, this appears in animals who, after years of close confinement are
transferred to a more enriched environment. These animals often fail to pay any
form of active attention to the new environment. Instead, they persist in the
performance of previous established abnormal patterns. Generally, animals
raised in more impoverished environments show less tendency to manipulate novel
objects than those raised under enriched conditions; isolated rats, for
example, do not move or climb objects, but investigates them in a less active,
more generally explorative fashion (such as sniffing) (Einon & Morgan,
1967; Renner & Rosenweig, 1986). Such observations suggest the attention
abilities of animals in prolonged captivity may gradually become impaired, and
it is meaningless to interpret abnormal behavior as a form of adaptation. To
investigate this hypothesis, novel objects should be presented to captive
animals over a prolonged period of time and their response toward these objects
should be recorded. Such research is presently under way at the Scottish
Agricultural College in Edinburg, Scotland. (Wemelsfelder)
Polar
Bear Behavior
Polar bears typically experience more
problems with confinement than most other animals. Captive polar bears are well
known for exhibiting repetitive behavior such as pacing back and forth,
particularly when housed in substandard, sensory-deprived exhibits. In fact,
pacing is so widespread in captive polar bears that the Dutch verb "to
pace" is to ijsberen or "to polar bear."
(Nielsen, 2003)
The most common
of such behaviors is unusual movement, for example, rocking from side to side
or pacing, whether it be back and forth or around in circles. Biting or
licking bars or walls also falls under the category of abnormal behavior, as is
the most disturbing behavior: self mutilation.
(Lindsay, 2001) They
are also extremely intelligent animals. This intelligence has
researchers at a dozen zoos across the United States studying polar bear
stress. They suspect that the reason captive polar bears show signs of stress
more frequently than other animals is primarily because they are so smart.
(Associated Press (AP), 2002)
PRACTICAL APPLICATIONS:
ENVIRONMENTAL ENRICHMENT IN CAPTIVE ANIMALS
Providing enrichments for a
large and diverse collection of exotic animals takes both time and financial
resources. At the San Diego Zoo and San
Diego Wild Animal Park they have an Animal Behavior Management department that
has responsibility for developing enrichment strategies for the animals in
their collection. They also have an
enrichment library where, just like the public book library, keepers are free
to check out enrichment items that have been pre-approved by the veterinary
staff for selected species. The Behavior
Management department stocks and maintains the library. Items in the enrichment library include;
animal scents, extracts, smear foods, hair from other animals, puzzle feeder
devices, and a variety of toys.
Providing animals the
opportunity to make choices and express a wide range of species-typical
behaviors is not without its risks. All
enrichment items, whether food or non-food are first approved by the veterinary staff as it is they who ultimately must deal with a medical
problem should one arise due to an enrichment item. Food enrichments come from the animal’s
regular diet.
The original goal for the
enrichment library was to create a means for the zoo’s nutritionist and one of
the staff veterinarians to review a particular item or strategy and approve it
for an entire taxa. But due to
behavioral idiosyncrasies of individual animals or nutritional peculiarities of
certain species, attaining the goal of a broad-based taxonomic approval has
proved elusive. In San Diego, the
reality is that most enrichments move through the approval process and are
approved for a single species or in some extreme cases, for a single
animal. Still they have developed a
system that works well and facilitates the enrichment of our animals by their
keeper staff. (Priest)
So
how can we prevent the development of states such as boredom and depression in
captive animals? The notion of animal boredom outlined in this paper suggests
successful enrichment should enhance the active character of behavior,
resulting in an increasingly frequency of interactive behaviors such as
exploration, manipulation, play, and social interaction. At the same time,
abnormal patterns of behavior should largely disappear. The question arises
whether great effort and expense must be made to achieve these aims, or whether
small and relatively simple beginnings can be made. Wemelsfelder suggests the latter is the case; if they are
applied in a way which is meaningful to the animal, simple and inexpensive
materials can have far reaching effects on the well-being of animals.
(Wemelsfelder)
METHODS OF BEHAVIOR
MANIPULATION
FOOD AND FOOD
PRESENTATION
The
presentation and variety of food items
in the animal’s diet is just one of the many strategies employed to add
complexity and variability to a captive animal’s life. Location, presentation, and time of food
delivery are important and may also
vary. Occasionally keepers will deposit
only the scent of food in an exhibit.
Just as they would in the wild, exhibit animals may spend hours looking
for the origin of the food scent. To
enhance randomness and variety where diet is concerned, sometimes food treats
or appropriate live items are placed in the exhibit. One popular enrichment strategy is to place
food treats inside a puzzle that the animal must manipulate in order to
dispense the food item. Sometimes, in
cases where processed foods are normally fed, exhibit animals may be given un-processed food or
even whole carcasses to feed on. Fur and
feathers can be important features for food handling to an animal. In carnivores, carcass feeding has been shown
to promote the health of the teeth, gums, and pallet (Ziegler, 1995). Varied presentation of food items can also be
enriching. Food items are sometimes
frozen in large blocks of ice. Animals
such as bears and elephants will investigate and manipulate ice blocks trying
to figure out a way to obtain the food item inside the frozen water. (Priest)
CHANGES TO THE
ENVIRONMENT
As
wild animals move through their habitats, the scenery changes. Environmental enrichment provides changes to
the scenery in exhibits. It may
include moving the components of the exhibit to different locations in the
exhibit, or removing them all together.
Or, it could include adding furniture in the form of piles of rocks and logs, or digging pits, or
placing other novel objects in the animal’s environment. These objects are deposited in an enclosure
and are available to be investigated, explored, and manipulated by the animal. (Priest)
PRESENTATION
OF LIVE PREY
Enrichment
may also involve the presentation of live prey.
In the United Kingdom, a study has been conducted on visitor attitudes
towards the feeding of live prey to exhibit animals (Ings, 1997.) According to this study, visitors generally
felt that “it is natural” and would only object because “it would upset them or
their children.” Similarly, in the
United States, public reaction to the feeding of live prey is a concern. In San Diego, they routinely feed enrichments
in the form of live meal worms and crickets with universal public
approval. They have also fed live fish
in a variety of public situations including shows, exhibits pools, and exhibits
with underwater viewing, all with little
negative public reaction. The predator
species list included; North American
river otter (Lutra canadensis), grizzly bear, (Ursus arctos), polar bear (Ursus
maritimus), fishing cat (Prionailurus viverrinus), tiger (Neofelis tigris),
gharial (Gavialis gangeticus), and various aquatic turtles. However, feeding a domestic chick or live
rabbit, to the same predator will produce a largely negative and unacceptable
public reaction. Clearly, zoos have some
work to do in the area of public
education about the food chain. The good
news for predators is that there has recently been some positive movement in
the direction of institutional willingness to feed small, live, warm-blooded
prey.
The
Grizzly Discovery Center in Yellowstone National Park, reports having “huge
success” in offering the gray wolf (Canis lupis) and the grizzly bear (Ursus
arctos horribilis) live rats as an occasional enrichment item (Heine, 1998).
While the predators are secure in
their dens, two to five rats are released in the habitat. Investigators report that successful hunts
have lasted from two minutes to nine hours. About 15% of the time, the prey
species does sometimes escape the predator.
To prevent problems that might accompany an overpopulation of escapees, only male rats are used for release
in the exhibits. If the prey escapes the bears or wolves, it is captured if
possible and not placed back in the exhibit again. Grizzly Discovery Center stations
interpreters at the exhibit whose job it is to answer questions and describe the natural behaviors taking place
during the enrichment sessions.
So,
from the public’s perception, there seem to be at least two key variables to
being able to successfully offer live, small,
warm-blooded prey as enrichment.
They are: #1 The context in which it occurs, and #2 The visitor’s
perception of “fairness” to the prey animal.
Providing the prey species with cover and multiple hiding places extends
the value of the enrichment for the predator and may also contribute to the zoo
visitor’s sense of “fairness” by making provisions for the fate of the prey in
the event it escapes the predator.
Offering
live enrichments to captive predators is an area that will require some further
study and a great deal of sensitivity for the social concerns that may be
associated with it. (Priest)
EVALUATION
With the use of the above-mentioned
tactics, it has been observed that captive animals, including polar bears have
greatly diminished their stereotypic behavior.
It is because they can work out their hunting skills and are able to
roam their confinement more freely, as polar bears are nomadic animals. Thus, they have more things to do
which decreases their boredom.
CONCLUSION
By
examining the scientific literature regarding stereotypic behavior in polar
bears and other captive animals, I can say that environmental factors such as
cage size, housing type, stress and boredom are the primary reasons why they
undergo abnormal behavior or stereotype.
When
a polar bear has come to this stage, he mostly paces back
and forth or around in circles. He also bites or licks bars or walls and
the most disturbing behavior: self mutilation.
However, with the proper behavior manipulation process such as
environment enrichment, such behaviors may diminish and give the polar bears a
better lifestyle.
REFERENCES:
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Associated Press (AP) (2002) “Beating Polar Bear Boredom”
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April 19, 2003
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Broom, D.M., Mendl, M.T. and Zanella, AJ (1995) “A Comparison
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Dantzer, R (1986) Behavioral, physiological and Functional
Aspects of Stereotyped Behavior: A
Review and Reinterpretation. Journal of
Animal Science pp. 1776-1786
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The Shape of Enrichment. 4
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