Marsden, M. D., Wood-Gush, D. G. M. 1986. A note on the behaviour of individually-penned sheep regarding their use for research purposes. Animal Production 42, 157-159.

Sheep are commonly housed in small individual pens for research purposes. ... The nature and extent of the abnormal behaviour found may be indicative of a differing background physiological state in these experimental animals from those in most common practical situations.Sheep kept in individual pens develop locomotor stereotypies, including repetitive butting, leaping up and down, weaving and route-tracing.