Stereotypies, compulsions, and normal behavior in the context of motor routines in the rock hyrax (Procavia capensis)

In the present study, we propose that the level of activity and organization in time and in space are the common link between motor routines in normal behavior, stereotypies, and compulsions. Specifically, an increase in activity, a shrinkage of the attended space, or an extension of time results in repetitive performance. This hypothesis is based on a discussion of stereotypies and compulsions in the context of motor routines in undisturbed behavior of the rock hyrax. Observations of hyraxes in the wild and in captivity revealed that their behavior constitutes motor routines at several levels of organization: (1) Activity is concentrated in a relatively limited region - A bush and an adjacent rocky ramp; (2) in both morning and afternoon, the hyraxes ascend the external branches of the bush, which they then leave in order to forage; (3) moving from the bush to the ramp and vice versa occurs along certain fixed routes; (4) while on the ramp, hyraxes tend to stop frequently on only certain fixed stones; (5) each such 'preferred stone' has a typical location and directions of approach and departure; and (6) motor performance on the 'preferred' stones typically involves crouching or sitting in certain typical postures, and is preceded and followed by only a few (if any) lateral movements. We propose that these recurrent behavioral patterns may constitute the normal foundation from which a reminiscent rigid motor performance that characterizes stereotypy and compulsive behavior develops.