Recognizing and Balancing the Benefits and Risks of Environmental Enrichment
American Association of Zoo Veterinarians Conference 1998

Ann E. Duncan, DVM

Detroit Zoological Institute, Royal Oak, MI, USA


As veterinarians, we each are in a position to impact the success and scope of enrichment activities taking place at our zoo. Our most basic involvement with enrichment often is to decide which enrichment techniques can be used safely for animals in our collection. There are basically two issues to consider. First, does this item pose a risk to the animal and, second, will this item provide any benefit to the animal? One of the veterinary medical credos is “above all, do no harm,” so it is logical for veterinarians to want to err on the side of caution. As we become more adept at providing for the physical and medical needs of the animals under our care, we need to turn our attention toward their psychologic needs. Providing environments that stimulate a greater range of natural behaviors, decrease stress, and increase activity is the next step towards optimizing health.

The scientist in me likes to see proof that enrichment works; I want to know that enrichment efforts will pay off and provide real benefits to animals. The more familiar I have become with enrichment literature, the more convinced I have become of the benefits to animal health.

With research, it has been demonstrated that enrichment can provide solutions to some of the behavioral and veterinary problems we encounter in captive animals and can improve overall well-being. One problem that can be addressed is autoaggression or self-directed behavior. Hair plucking and self-biting in primates, feather plucking in birds and tail sucking/chewing in cats are all examples of self-aggressive behaviors seen in zoos. These behaviors have been alleviated or reduced by providing enrichment activities designed to provide more opportunities for natural behaviors such as foraging or food manipulation.2,11 Aggression, stereotypic locomotion and low activity level can also be reduced with certain enrichment strategies.9,10,12 Regurgitation and reingestion (r/r) is an abnormal behavior seen in great apes that has been shown to be reduced in animals offered browse, straw, and other forage items.1,3 Dental health can be improved with the provision of bones and rawhide chew toys.5,6

Veterinary cases are also made manageable through operant conditioning, often considered a form of enrichment. At the Detroit Zoo, we have been able to train 2/3 of our 15 chimps to accept hand injections of anesthetic drugs. This has made annual physical exams much less stressful for both the animals and the personnel involved. With similar techniques other zoos have been able to manage a diabetic drill baboon with regular blood collection and insulin injections, use a blood pressure cuff to monitor woolly monkeys with hypertension and train a macaque to present its neonate for supplemental bottle feedings.7,8 Hoofstock have been able to be conditioned for venipuncture and other veterinary procedures.4 In the hospital, we use enrichment for patients that need to be pulled from social groups during a time of healing. There are numerous examples of animals that could not have been treated successfully without these techniques.

The risks associated with enrichment can be thought of as either physical or behavioral. When we think about physical risks, we think about animals becoming caught in tires, impacting on burlap bags, or becoming sick after eating non-processed food items like live fish. There is almost nothing in the literature about enrichment hazards, so we find it necessary to anticipate potential problems. It is sometimes hard to separate problems associated with enrichment from problems associated with captive living in general. It is my impression that the incidence of enrichment related injury and death is very low. Many accidents occur because of poor coordination of enrichment efforts or lack of maintenance of enrichment items and exhibit features. If we compare an enriched exhibit to a barren one, it is obvious an enriched environment is more complex and will present more dangers if not properly maintained. Perhaps the larger risk is spending valuable time on enrichment techniques that are not effective or do not provide the greatest potential benefit. Without assessing our efforts, we risk cluttering animal enclosures with objects that are of little interest to animals and have no positive impact on behavior.

Both the physical risks and behavioral risks can be diminished by setting up a program to coordinate enrichment efforts. Program paperwork does not have to be complex or time-consuming but should provide basic information to allow enrichment ideas to be evaluated and improve in efficacy over time. Individual enrichment ideas can be thought of as falling somewhere on a continuum of low risk to high risk and a continuum of low benefit to high benefit. The goal should always be to maximize benefit with the lowest risk. Keepers should be encouraged to try new and creative ideas that meet this goal while learning to fine tune techniques and make simple ideas more effective.

Enrichment is an effective tool for solving many problems found in captive animals. The potential benefits of a well-executed enrichment program are numerous. By understanding and being familiar with research, we can identify trends and define enrichment strategies most likely to provide widespread benefit in our collections. We can start to design environments that not only address specific problems but meet the physical and psychologic needs of animals.

Literature Cited

1.  Baker, K. 1997. Straw and forage material ameliorate abnormal behaviors in adult chimpanzees. Zoo Biol. 16:225–236.

2.  Chamove, A., J. Anderson and V. Nash. 1984. Social and environmental influences on self-aggression in monkeys. Primates. 25(3):319–325.

3.  Gould, E. and M. Bres. 1986. Regurgitation and reingestion in captive gorillas: description and intervention. Zoo Biol. 5:241–250.

4.  Grandin, T. and M. Phillips. 1996. The advantage of training antelope to cooperate with veterinary procedures. In: Proc Assoc Zoos and Aquariums Regional Conference. 562–567.

5.  Haberstroh, L., D. Ullrey, J. Sikarskie, N. Richter, B. Colmery, T. Myers. 1984. Diet and oral health in captive Amur tigers (Panthera tigris altaica). J Zoo Wildl Med. 15:142–146.

6.  Lage, A., N. Lausen, R. Tracy, E. Allred. 1990. Effect of chewing rawhide and cereal biscuit on removal of dental calculus in dogs. J Am Vet Med Assoc. 197(2):213–219.

7.  Laule, G., R. Thurston, P. Alford and M. Bloomsmith. 1996.Training to reliably obtain blood and urine samples from a diabetic chimpanzee (Pan troglodytes). Zoo Biol. 15:587–591.

8.  Logsdon, S. and S. Taylor. 1995. Use of operant conditioning to assist in the medical management of hypertension in woolly monkeys. In: Proc Assoc Zoos and Aquariums Regional Conference. 96–102.

9.  Paquette, D. and J. Prescott. 1988. Use of novel objects to enhance environments of captive chimpanzees. Zoo Biol. 7:15–23.

10.  Shepherdson, D., K. Carlstead, J. Mellen, J. Seidensticker. 1993. The influence of food presentation on the behavior of small cats in confined environments. Zoo Biol. 12:203–216.

11.  van Hoek, C. and C. King. 1997. Causation and influence of environmental enrichment on feather picking of the crimson-bellied conure (Pyrrhura perlata perlata). Zoo Biol. 16:161–172.

12.  Wilson, S. 1982. Environmental influences on the activity of great apes. Zoo Biol. 1:201–209.


Speaker Information
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Ann E. Duncan, DVM
Detroit Zoological Institute
Royal Oak, MI, USA

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