Slip-shod or safely shod: the bighorn sheep as a natural model for research

Over a million injuries caused by slipping of footwear are believed to require treatment by doctors every year in the United Kingdom and many domestic animals are injured by slipping. Recent research has revealed that surface roughness of solings and floors is an important determinant of grip on lubricated surfaces and it is also known that soling friction is affected by hardness. The bighorn sheep (Ovis canadensis) an animal species which has adapted to a slippery environment, was studied to elucidate optimum roughness and hardness and other features which influence grip. Four adult ewes were examined in the London Zoo. The cloven hooves of this species are very mobile and the cranial tips of the hooves are the first parts to make contact with the ground. A very small contact area ensures penetration of a film of water. Mean roughness of the contact area was found to be 53 microns Rtm and the mean hardness 63 Shore A. These characteristics appear to facilitate an excellent grip on wet slippery rock but not on smooth ice. Further studies of the feet of wild species could contribute to an understanding of the factors which determine the safety of solings and floors.