Refinements to captive chimpanzee ( Pan troglodytes ) care: a self-medication Paradigm

Abstract

In an effort to enhance welfare, behavioural management continually refines methods of non-human primate (NHP) care. Chimpanzees (Pan troglodytes) are one of the most cognitively complex captive NHPs and they have been observed to self-medicate in the wild. The population of captive chimpanzees in the US is aged (due to a breeding moratorium instituted in 1998) and will progressively require more medical care as they get older. To functionally simulate natural self-medication behaviour, provide chimpanzees with the opportunity to voluntarily participate in their own healthcare, and open new avenues of communication between caregivers and chimpanzees, we used a medication choice paradigm that allowed chimpanzees to choose their daily arthritis medication. We provided four arthritic, mobility-impaired chimpanzees with meloxicam or ibuprofen in blue or green Gatorade® to establish associations between the coloured drinks and the effects of the medications. We subsequently gave each chimpanzee a choice between the two medications. Behaviour was recorded using 15-min focal animal observations. Mobility was assessed using interactive mobility tests and a caregiver-rating system. One chimpanzee showed a medication preference (ibuprofen over meloxicam). The chimpanzees exhibited no significant behavioural or mobility differences over time, suggesting that ibuprofen and meloxicam may not differ significantly in their ability to alleviate arthritic symptoms. Whether or not the chimpanzees show a medication preference, the opportunity to make meaningful choices and the functional simulation of a complex behaviour, self-medication, is present when using this medication choice technique. Furthermore, the paradigm itself could have potential applications for additional medication options and treatment regimens.

Keywords: animal welfare; behavioural management; captivity; chimpanzees; choice; voluntary participation.

Figure 1

Corral housing. Several ramps serve as easy access climbing paths for mobility-impaired chimpanzees.

Figure 2

Dome housing (see also Figure 3). Several ramps serve as easy access climbing paths for mobility-impaired chimpanzees.

Figure 3

Figure 4

Mobility test schematic (not to scale). Yellow circles = targets, arrows = direction of movement. A) Two chimpanzees moved to and touched four targets one at a time as directed by the experimenter. Each individual arrow represents approximately 2 m of distance. B) One chimpanzee moved to and touched four targets one at a time as directed by the experimenter. Vertical arrows represent approximately 1 m of distance and the horizontal arrow represents approximately 2 m of distance. C) One chimpanzee moved to and touched two targets as directed by the experimenter. Each arrow represents approximately 3 m of distance.

Figure 5

Chimpanzee medication choices. Total number of times each chimpanzee chose meloxicam or ibuprofen over the course of the approximately one-month Choice phase.

Figure 6

Percentage of time spent rough-scratching. Median percentage of time chimpanzees spent rough-scratching within each study phase.

Figure 7

Percentage of time spent locomoting. Median percentage of time chimpanzees spent locomoting within each study phase

Figure 8

Mobility scores across phase. Observer ratings of each chimpanzee’s overall mobility on a scale of 6–30. Higher scores indicate higher impairment in mobility (6 = least impaired). Intraclass correlation = 0.931. Error bars represent standard error of the mean.

Figure 9

Mobility test speed. Chimpanzee speed (m s⁻¹) to complete the mobility test (see Figure 4 for Mobility test schematic) across study phase. Error bars represent standard error of the mean.

Figure 10

Mobility test latency. Chimpanzee latency (s) to begin the mobility test (ie time to touch first target of mobility test) across study phase. Error bars represent standard error of the mean.