Behavioral and Medical Therapy for Self-Mutilation and Generalized Anxiety in a Bonobo (Pan paniscus)
American Association of Zoo Veterinarians Conference 1998
Roberta S. Wallace1, DVM; Barbara Bell1; Harry Prosen2, MD, MSc; Victoria Clyde1, DVM
1Milwaukee County Zoo, Milwaukee, WI, USA; 2Medical College of Wisconsin, Wauwatosa, WI, USA

Case Report

Treatment of abnormal or undesirable behaviors with behavior modification and medical therapy is relatively new to the field of veterinary medicine. Few published reports on the use of antidepressants and antipsychotic drugs in exotic animals exist.2 This report describes the successful treatment of a nonhuman primate with a combination of behavior and medical therapy based on extrapolation of similar treatments used in human psychiatric medicine.

On July 8, 1997, the Milwaukee County Zoo (MCZ) received “Brian,” an 8.5-year-old, 35-kg male bonobo (Pan paniscus) from another institution. The animal was born at that institution and had been housed with its father and other troop members until 7.5 years of age. Reports from the staff indicated that the bonobo was regularly severely intimidated by its father. During this time, the bonobo developed the persistent self-mutilating behavior of inserting its fingers and/or entire hand into its rectum (termed “fisting”).

Believing that this behavior may have been caused by chronic stress and mental trauma, the animal was removed from the group in October 1996, and housed in isolation for 8 months prior to its arrival at the MCZ. The “fisting” behavior continued while in isolation, occasionally with enough intensity to cause rectal bleeding. Treatment with acepromazine 12.5 mg orally every 8 hours was begun in November 1996. Effects were minimal and treatment was discontinued shortly thereafter. Magnetic resonance imaging was performed in December 1996 to determine if an underlying physical problem was causing the behavior. The rectum and lower colon were palpably thickened, which was attributed to chronic trauma; however, no other abnormalities were noted. Treatment with fluoxetine (Prozac, Eli Lilly & Co., Indianapolis, IN, USA) 16 mg orally once a day was initiated in December 1996, and 14 days later it was noted that there was improvement in both the severity and frequency of the “fisting” behavior. Therapy was continued until just prior to shipment to the MCZ. To try to provide the animal with a better social environment, it was sent to the MCZ for integration into a large group of bonobos. The bonobo troop consisted of one juvenile and four adult females, and two juvenile and two adult males. In addition, the MCZ has an active operant conditioning and medical behavioral training program, and it was hoped that behavioral therapy would reduce the self-mutilation behavior.

When the bonobo arrived at the MCZ, it seemed both angry and frightened. The keeper staff noted several behavioral abnormalities which included: inserting its fist into its rectum, inducing vomition, pacing, constant hand clapping, rubbing genitalia on sharp objects, self-mutilation by ripping at fingernails and toenails, inability to sleep or rest during the day, spitting and generalized aggression toward the keepers. Volunteer observers were recruited to monitor the type and frequency of these behaviors.

Behavior modification was used in an attempt to alleviate the problems; medical therapy was not immediately instituted. While isolated during the quarantine period, short training sessions praising desired behaviors, and ignoring undesirable behaviors were begun. Frequent small feedings were offered to keep the animal active and occupied. It was observed that induced vomition increased after fruit was eaten; therefore, fruit was removed from the diet, and the frequency of vomition decreased. Training and enrichment were difficult because the animal was extremely fearful of all new objects, including toys and food items used for behavioral enrichment. Nonetheless, some improvements in behavior were obtained, but after several weeks, improvement reached a plateau.

One and one-half months after arrival, the animal was cleared from quarantine and introduced to the other troop members. The animal was fearful of adult male bonobos, it had problems eating in a group, and it had poor play and reconciliation behaviors. Solutions to help the animal adapt included placing it in small social groupings with calm, gentle animals and keeping life routine and predictable. This strategy appeared to work for a couple months, when improvement stopped and behavior regressed.

A decision was made to seek consultation with a psychiatrist. The consultation included a “case conference” with zoo staff where the psychiatrist reviewed the animal’s developmental history and the dynamics of its seeming self-mutilating and obsessional “fisting.” There was agreement that the behavior increased when the bonobo was anxious or under stress and seemed to have both regressive and auto-erotic components to it. A plan was devised to use medications to deal with the obsessional anxiety, and behavioral efforts to introduce the animal to females and the usual matriarchal society of bonobos with the goal of promoting a more normal mature sexual outlet. The behavioral changes were staged to occur as the bonobo bonded with its keeper, allowed itself to be pampered by two female (older) companions and gradually resocialized with other bonobos. The process was accompanied by regular discussions with the consultant and modifications in the staging of socializing events according to the animal’s progress and improvement. All keeper-animal interactions were kept calm and positive. Many (≥5/day) short, positive training sessions were performed to integrate the animal into the medical behavior training program, and to keep it occupied in an attempt to decrease the undesirable behaviors.

Paroxetine (Paxil, SmithKline Beecham Pharmaceuticals, Philadelphia, PA) 10 mg was administered orally once a day initially, but after five days administration increased to twice a day. Within 1 week, the animal appeared calmer. Induced vomiting stopped after 2 weeks. Changes noted by the observers included slower eating habits, ability to rest/sleep during the day, cessation of pacing, decreased aggression toward the keepers, and an increased attention span during training sessions, with the ability to focus on tasks and learn new behaviors. The “fisting” behavior was reduced, but still occurred at perceived high anxiety times, such as immediately before meals. Diazepam 2.5 mg once daily in the morning was initiated to curb anxiety levels, with moderate success. Paroxetine is an antidepressant which acts as a potent and highly selective inhibitor of neuronal serotonin reuptake. In addition to its antidepressive effects, it is also highly effective in treating obsessive-compulsive disorders and panic disorders. Reported side effects in humans include nausea, somnolence, insomnia, dizziness, asthenia and ejaculatory disorders. Its use is contraindicated in patients taking monoamine oxidase inhibitors.1 Paroxetine was chosen over other selective serotonin reuptake inhibitors (SSRIs) because of its anti-obsessional effects, and because of its more immediate onset and the hope for quick reduction of anxiety.

The bonobo has now been introduced into the large bonobo group and is learning the social skills necessary to interact successfully with peers. The animal is successfully participating in the MCZ medical behavior training program. Although self-mutilation behaviors still occur occasionally, the animal continues to improve and adapt. Routine treatment with diazepam has been discontinued because of poor acceptance, without ill effects. It is hoped that with continued therapy, with adjustments as necessary, quality of life will remain high throughout the animal’s life span.

This case illustrates that behavioral and medical therapy, carefully chosen and implemented, can work effectively to treat undesirable and self-destructive traits exhibited by animals.

Literature Cited

1.  Physician’s Desk Reference. 51st ed. Montvale, NJ: Medical Economics; 1997:2681–2686.

2.  Teskey, G.C., P.A. Valentine, E.M.B. Poulsen, V. Honeyman, R.M. Cooper. Treatment of stereotypic behavior in the polar bear (Ursus maritimus). Proc. Amer. Assoc. Zoo Vet. 1996:334–336.


Speaker Information
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Roberta S. Wallace, DVM
Milwaukee County Zoo
Milwaukee, WI, USA

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