The Use of Positive Reinforcement Techniques in the Medical Management of Captive Animals
Positive reinforcement training is gaining acceptance as a valuable animal care and management tool to aid in husbandry activities, veterinary procedures, and research protocols. The benefits of such work include less stress on the animal, greater flexibility and reliability in data collection, and a reduced use of anesthesia. This paper presents examples of the use of training techniques to address various medical situations in a number of species in the zoological setting.
The comprehensive use of positive reinforcement training has revolutionized the way we care for captive animals.4,6 By using recognized techniques, many tangible results and benefits can be achieved. Animals are desensitized to frightening or painful events, like getting an injection, so the stress associated with these events is significantly reduced.5,7 Animals gain the opportunity to voluntarily cooperate in these procedures, rather than being forced to comply. With a greater accessibility to more cooperative animals comes the opportunity to initiate preventative medicine practices and to explore techniques previously seen as less practical on a routine basis such as ultrasound or tube insertions for artificial insemination.3 With this cooperation comes a reduction in the use of restraint and anesthesia.1 Many husbandry and veterinary procedures can be implemented with less disruption to all animals, by reducing the need to separate animals from their social groups for many procedures. Finally, experience has shown that trained animals maintain a high degree of reliability in participating in these procedures and are less stressed while doing so.8
The training referred to throughout this paper, and recommended as the approach of choice, is positive reinforcement training. Animals are reinforced with pleasurable rewards for the desired behavioral response. Operationally, it means that the positive alternatives are exhausted before any kind of negative reinforcement is used. On the rare occasions when an escape-avoidance technique is necessary, it is kept to a minimum and balanced by positive reinforcement the vast majority of the time. Punishment, which by definition is used to eliminate a behavior, is only appropriate in a life-threatening situation for person or animal. To dispel a common misperception, positive reinforcement training does not require any food deprivation. Animals are fed their daily allotment of food, and rewards for training use that diet, or consist of extra treats. Finally, this training relies on voluntary cooperation by the animal to be successful.
Through a process termed desensitization, animals learn to tolerate presumably scary or uncomfortable stimuli. In basic terms, desensitization is a process designed to “train out,” or overcome, fear. By pairing positive rewards with any action or object that elicits fear, that fearful entity slowly becomes less negative, less scary, and presumably less stressful. Using this technique, animals have been desensitized to husbandry and veterinary procedures, new enclosures, unfamiliar people, negatively perceived people like the veterinarian, novel objects, strange noises, and other possible aversive stimuli. In fact, the authors have previously reported that animals being desensitized to specific stimuli can, over time, become generally desensitized to anything novel or unexpected.2
Voluntary Acceptance of Injections
One of the most useful applications of husbandry training is the conditioning of animals to voluntarily accept injections. When training an animal to accept an injection, the feeling of a needle piercing the skin is a potentially frightening and painful experience. Effective desensitization requires pairing many positive rewards directly with that experience, or with a similar experience. Training may include pairing positive rewards with the experience of being touched with a progression of items, starting with the trainer’s finger, then a capped syringe, and then to a needle with the end cut off so it is blunted, and finally the real needle. The animal must experience this over and over again, with the touch slowly moving from very light to the final experience of actually piercing the skin. If desensitization is done well, the animal will voluntarily accept the injection and recognizable signs of stress and fear will be diminished or absent. To date, injection training has been successfully implemented with many different species and it continues to be a priority behavior for many zoos.
Husbandry Training of Elephants in Protected Contact
Protected contact, as a system for managing elephants, is based on the use of positive reinforcement techniques. All elephants in protected contact should be trained on a wide range of husbandry behaviors, including skin care, body exam, foot care, tusk trimming, blood sampling, vaginal exam, and rectal palpation. Until very recently, many in the zoo community were skeptical of the ability to provide comprehensive medical care for animals functioning in a positive reinforcement-based system where compliance in behaviors is voluntary. That skepticism is eroding away as more examples of successful medical treatment under these conditions are being produced. The following examples illustrate the advances being made in the management of elephants in protected contact.
The Houston Zoo manages two male and four female Asian elephants in a protected contact system. Thailand, the 33-year-old bull, has had chronic nail cracks and abscesses in its front feet for over 10 years. Prior to protected contact, this elephant was maintained in a no contact system, which meant no routine foot care was being performed. Even as nail condition worsened, only minimal foot work was possible. With the introduction of protected contact and positive reinforcement techniques, the animal was easily trained to present its feet through an opening in the training wall or the barn door for foot work.
Over the past 5 years, the elephant has tolerated routine trimming as well as deep trimming into the abscessed areas. The animal has also complied in daily treatment of the abscesses and regular foot soaks in Epsom salts or Nolvasan (Chlorhexidine diacetate, Fort Dodge Animal Health, Overland Park, KS, USA) and warm water once or twice daily for 10 minutes. With the expanded access to the elephant, cooperation with diagnostic techniques was now possible. Radiographs were taken to determine the depth of the infected tissues and to see if there was any bony involvement. Radio-opaque dye was injected into the hole in the foot so that the tract could be identified. The elephant was trained for the procedure by first teaching the animal to extend a front leg through the foot hole and place its foot on a custom-built footrest. Next an old radiograph cassette was used to train the animal to hold steady with the plate in a variety of positions under and around its foot. The final step was to move the large machine in position for the procedure while the animal placed and held its foot in the proper positions.
Currently, the animal’s feet are greatly improved. Granulation beds have formed where the abscesses were, and only small holes are visible on each foot. Routine foot care continues. The feet of this elephant will always be a concern, but through training, the keepers and veterinarians maintain the ability to monitor and treat the animal’s condition, as necessary.
In another case, Kiba, a young bull, was born at the zoo in 1987 with an umbilical stump that was excessively long and soon became infected. Although it was treated daily with Betadine (Purdue Frederick, Norwalk, CT, USA) the infection persisted, and a cantaloupe sized bulge remained present on its abdomen. In February 1992, the elephant was sedated and an ultrasound exam on the herniated area was done, specifically, to check the integrity of the abdominal wall and the potential for entrapment of intestinal loops. The ultrasound showed the area to have healed well. In November 1995, the animal’s umbilical area appeared very swollen. The immediate concern was that a loop of bowel had become trapped in a previously undetected defect. An ultrasound was again needed, but this time, the elephant staff had the opportunity to train the elephant for this procedure. The animal was taught to present its body parallel to the training wall. The animal was then desensitized to the ultrasound exam including palpation of the area, the close proximity of the equipment, the feeling of the contact gel, and pressure of the transducer.
This elephant is an extremely responsive animal and was ready for the ultrasound within days. Fortunately, the ultrasound showed no loops of bowel or defects; the swelling was likely due to mild trauma. The swelling decreased within 2 weeks and has not reoccurred.
Medical Training and the Human/Animal Bond
In November 1994, trainers noticed that lower teeth appeared loose, and ulcerations were present on the mandibular tissue in a California sea lion, Gertie. In December, the animal was immobilized for a biopsy of the ulcerations and to radiograph the mandible. The lower left incisors had severe bone resorption around the roots; the adjacent teeth (right central incisor and left canine) were loose and easily removed. The animal’s condition significantly worsened when a pronounced swelling at the medial aspect of the lower left premolar appeared. Due to the severe deterioration of the mandible, a mandibulectomy was scheduled. The oral lesions appeared aggressive and necrotic, predominantly involving the proximal left mandible, part of the right, and the surrounding tissue. Diagnosis showed widespread squamous cell carcinoma throughout the lower mandible.
The prognosis for such a radical surgical procedure was not favorable, but the sea lion came through the procedure better than expected. Several days following the surgery, the animal was completely lethargic, not eating, and in an overall depressed condition. The animal was injected with analgesic antibiotics but little to no response was the result. The decision to euthanatize the animal was made as her condition worsened and recovery seemed unlikely. A trainer with a 7-year history training this animal in a variety of husbandry and show behaviors was brought in as a last resort. Immediately, the sea lion responded to the trainer and was eating fish within days. A diverse behavioral repertoire offered many options to monitor the healing progress as well as help the animal relearn to eat. The animal was trained for a full mouth exam, allowing all teeth and areas of the mouth to be touched and manipulated. This behavior proved instrumental in the recovery. As the area began to heal, suture material had to be trimmed as it worked out of the tissue. This involved the animal holding its mouth open and allowing scissors in and around the surgery site. Topical treatment and cleaning of the site was required, and the animal tolerated this remarkably well.
The sea lion’s recovery took over 3 months but was fully successful. The animal was reintroduced to the group and the exhibit pool. Full recovery was largely due to the training that had occurred in the years before the surgery and the trust between animal and trainer that is an inherent and powerful part of positive reinforcement training.
The Versatility of Husbandry Training
As husbandry training grows in the zoological community, many applications and benefits not initially perceived continue to emerge. Some examples of novel application of husbandry training include:
- Getting saliva samples on cotton balls from gorillas
- Training free-ranging hoofstock to accept yearly vaccinations
- Milking a female rhinoceros for supplementation of hand raised offspring
- Performing a vaginal swab on a female warthog
- Training female drill baboons on tube insertion for artificial insemination
- Blood collection on rhinos, tapirs, and adult chimpanzees
- Getting weights on rhino, pygmy hippos, giant anteater, and tapirs
- Holding giant anteaters on target while body measurements are taken
In conclusion, positive reinforcement training is gaining stature among animal managers and veterinarians as a useful tool for enhancing animal health and husbandry. The applied use of positive reinforcement techniques provides the means to proactively address a wide range of medical conditions and to develop and implement an effective program of preventative medicine. These benefits make training a valuable part of any animal management program and have significant implications for overall animal care and welfare.
1. Bloomsmith, M. 1992. Chimpanzee training and behavioral research: a symbiotic relationship. In: Proceedings of the American Association of Zoological Parks and Aquariums National Conference. 403–410.
2. Desmond, T. and G. Laule. 1991. Protected contact elephant training. In: Proceedings of the American Association of Zoological Parks and Aquariums National Conference. 607–611.
3. Desmond, T., G. Laule, and J. McNary. 1987. Training to enhance socialization and reproduction in drills. In: Proceedings of the American Association of Zoological Parks and Aquariums National Conference. 435–441.
4. Laule, G. and T. Desmond. 1994. Use of positive reinforcement techniques to enhance animal care, research, and well-being. In: Proceedings, Wildlife Mammals as Research Models: In the Laboratory and Field. American Veterinary Medical Association. 53–59.
5. Moseley, J. and J. Davis. 1989. Psychological enrichment techniques and new world monkey restraint device reduce colony management time. Laboratory Animal Science. 39:31–33.
6. Reichard, T. and W. Shellabarger. 1992. Training for husbandry and medical purposes. In: Proceedings of the American Association of Zoological Parks and Aquariums National Conference. 396–402.
7. Reinhardt, V. 1992. Improved handling of experimental rhesus monkeys. In: H. Davis and A. Balfour (eds) The Inevitable Bond: Examining Scientist-Animal Interactions. Cambridge University Press, Cambridge. 171–177.
8. Reinhardt, V., D. Cowley, J. Scheffler, R. Vertein, and F. Wegner. 1990. Cortisol response of female rhesus monkeys to venipuncture in homecage versus venipuncture in restraint apparatus. J Med Primatology. 19:601–606.