A new method of walking rehabilitation using cognitive tasks in an adult chimpanzee (Pan troglodytes) with a disability: a case study.

There are few studies of long-term care and rehabilitation of animals which acquired physical disabilities in captivity, despite their importance for welfare. An adult male chimpanzee named Reo at the Primate Research Institute of Kyoto University, developed acute myelitis, inflammation of the spinal cord, which resulted in impaired leg function. This report describes a walking rehabilitation system set up in a rehabilitation room where he lives. The rehabilitation apparatus consisted of a touch monitor presenting cognitive tasks and a feeder presenting food rewards at a distance of two meters from the monitor, to encourage him to walk between the monitor and the feeder repeatedly. Initially, Reo did not touch the monitor, therefore we needed adjustment of the apparatus and procedure. After the habituation to the monitor and cognitive tasks, he started to show behaviors of saving food rewards without walking, or stopping participation to the rehabilitation. Finally it took seven phases of the adjustment to determine the final setting; when the monitor automatically displayed trials in 4-h, AM (1000-1200 hours) and PM (1400-1600 hours) sessions through a day, Reo spontaneously walked from the monitor to the feeder to receive rewards, and returned to the monitor to perform the next trial. Comparison of Reo's locomotion in a no-task period and under the final setting revealed that the total travel distance increased from 136.7 to 506.3 m, movement patterns became multiple, and the percentage of walking increased from 1.2 to 27.2 % in PM session. The findings of this case study suggest that cognitive tasks may be a useful way to rehabilitate physically disabled chimpanzees, and thus improve their welfare in captivity.