Stereotypic Movements in Zoo Animals
Abnormal behaviour such as a stereotypic movement is very much a concern when it occurs in relation to animals held in captivity. From a behavioural standpoint, the behavioural and spatial requirements of nondomestic animals in captivity greatly depends on the species. For example, the behavioural requirements of many species appear relatively simple when compared with the requirements of a highly specialized carnivorous species such a large cat. It is often in predators or primates that one observes abnormal behaviours such as stereotypic movements that are uncommon or otherwise different than normally occurring by the species in its natural environment.
How do you identify a stereotypic movement?
First it may be useful for the zookeeper or the veterinarian to identify the abnormal behaviour (the stereotypic movement) as one that occurs by the nondomestic animal in the captive and not in the species' natural habitat. For example, pacing at the fence of an enclosure is a behaviour that has not been observed in the natural habitat due to the lack of enforced boundaries in their wild environment. A stereotypic movement can be further categorized as either one that has no obvious function and is a movement repeated regularly or as a repeated movement that is an exaggerated form of a purposeful behaviour. An example of the first type of stereotypic behaviour is the figure eight or circular pacing often observed by captive bears. Compulsive scent marking reportedly observed in marten species, although initially part of the animal's normal repertoire, can be identified as example of the latter type of stereotypic movement.
Two basic forms of stereotypic movements found in the zoo environment are pacing and stationary. Pacing occurs when the animal moves repeatedly back and forth in a straight line or perhaps moves in a circular or figure eight pattern in its enclosure. The straight line pacing is most often observed at the boundary of an enclosure. The most common stationary movements are repeated nonlocomotive acts such as rocking, head tossing or weaving.
What is the cause of the stereotypic movements?
One likely cause of these abnormal behaviours is the lack of appropriate normal stimuli which contributes to boredom and the lack of exercise (inactivity). It has been suggested that stereotypic movements may also develop as escape attempts that cannot be carried out completely because of the inadequate space in their environment. As well, the proximity to other animals and to the public may play roles in the initiation of a stereotypic movement. One example of how a stereotypic movement may evolve is a scenario of the predatory animal waiting for the zookeeper to deliver its meal. At feeding time the animal is usually waiting at a specific location in its enclosure. While the animal is awaiting its meal, the animal may turn around in restlessness and follow a fixed path back to its original lookout. This sequence of events initiates a stereotypical movement that may occur at feeding time and may eventually occur whenever the animal is hungry. This in an example of how an insignificant behaviour such as waiting for a meal (predatory animals for the most part do not wait for a meal to be delivered to them in the wild) can transform itself into a stereotypic behaviour.
How can the frequency of stereotypic behaviours be reduced?
When it is presumed that a stereotypic behaviour developed due to a lack of novel stimuli then it should be investigated whether the present enclosure or housing condition is naturalistic so that it closely resembles the habitat the animal would occupy in the wild. When this is determined, appropriate steps to introduce the animal to a more complex environment should be carried out which may alleviate or decrease the stereotypic movement. Another approach to reduce the stereotypic movement while increasing sensory stimulation to the animal is through behavioural engineering. This technique utilizes mechanical devices that provide food as a reward in response to behaviours that have been selected for through positive reinforcement. One successful attempt using behavioural engineering to reduce the frequency of pacing in jaguars was to condition the animals to rear up and strike a paddle with their forepaw. This behaviour was initiated when the jaguars heard food entering an automatic feeder mounted in their enclosure. This treatment ultimately increased the jaguars alertness and significantly decreased the stereotypic pacing. A third approach to providing novel stimuli in the enclosure is to install automatic dispensers that release food randomly throughout the day. For example, the introduction of flying meatballs in a carnivore enclosure provides an artificial prey which stimulates the predatory behaviour of an animal such as the serval cat which leaps to catch its prey. As well, fish released into a polar bear pool can reduce the stereotypic behaviour observed in captive polar bears (for example begging, rocking motions) by increasing the activity of the animal. In summary, the causes of stereotypic movements associated with nondomestic animals kept in zoos are very complex as briefly illustrated by this text. Steps can be taken to design habitats and devices the meet both the behavioural and spatial requirements of the captive animal which may help to alleviate or reduce the frequency of the stereotypic movements observed.
Stevenson, M.F. The captive environment: its effect on exploratory and related behavioural responses in wild animals. In Exploration in animals and man. (J. Archer and L. Birke, eds.) Van Nostrand Rheinhold, UK, 1983; pp. 176-197.
Meyer-Holzapfel, M. Abnormal behaviour in zoo animals. In Abnormal behaviour in animals. (M.W. Fox ed.) W.B. Saunders Co., Philadelphia, PA, 1968; pp. 476-502.
Hediger, H. Wild animals in captivity. Dover publications, New York, NY, 1964; pp.71-77.