Preferred rolling places
Horses usually choose one or two preferred rolling spots and this may help to establish herd bonding by coating them in the ‘herd smell’. Wild horses and zebras have rolling rituals, with herd members taking turns to use the rolling spot.
Stabled horses often paw the bed and roll when they are put into a new stable or if clean bedding has been put down. It is thought that they do this to cover the bedding with their own smell.
The rolling sequence
The horse begins the rolling sequence by starting to lie down as it normally would. The horse lowers its head right down to the ground, moving the centre of gravity both forwards and down. The hind legs are moved forwards underneath the body and the horse begins to bend at the knees (Figs 13.2–13.4).
The stance is highly characteristic, and if a ridden horse begins to get down, the rider can feel the horse’s posture change and must ride the horse forwards quickly. Frequently, hot sweaty ponies find the temptation to roll almost irresistible and must be watched carefully all the time they are halted if their young riders are to avoid embarrassment!
The horse gently lowers itself to its knees, folding the lower leg underneath its chest (Figs 13.5–13.7). At the same time the hocks and stifles flex, allowing the hindquarters to sink. Once the horse has achieved this position it lets its body and hindquarters flop onto the ground.
The ribs and pelvis
The unusual angle in Fig. 13.6 shows the both the spring of the ribs and the position of the pelvis, which can be seen behind the ribcage. In the standing horse it is hard to appreciate the size of these structures, and it is only when the horse is rolling or lying down that the size becomes apparent.
Once the horse is down it lets itself fall to one side. It then rubs the side of its head, neck and body before kicking powerfully against the ground to roll over onto its back. Once on its back the horse rubs its back and rump against the ground (Fig. 13.8).
Many horses will have a preferred side on which they get down first. Some horses are able to roll over to the other side (Fig. 13.11), whereas others have to get up, then get down again to groom the other side. These horses sometimes only roll on one side or the other. Those that find rolling over easy may roll back and forth several times before they get up. It is said to be the sign of an athletic horse with good conformation that is free from back pain, if it can roll right over. However, overweight horses and those with very high withers may not be able to do this.
It is difficult to visualise the anatomy of the pelvis from two-dimensional diagrams and from looking at the horse from the side. At the top of the hindquarters is the croup (tuber sacrale), below that is the point of the hip (tuber coxae) and below that the hip joint where the femur articulates with the pelvis. From the angle shown in Fig. 13.12 it is easier to see the pelvis as a ring of bone, attaching to the spine and hind limbs. Fig. 13.12 also shows a clear view of the horse’s sternum. From Fig. 13.13 it is possible to appreciate the sheer size of the muscles of the upper thigh and area occupied by the gut, where there is little skeletal muscle.