Rolling Along

Dear Dr. McDonnell, Almost every time I let my horses out of the stalls after feeding them, they roll in the dirt, dust, or mud. Why? Mike and Sharon Rolling associated with turnout after feeding is a slight variation on the more usual question of rolling immediately after a good grooming or a bath. Owners often ask why their horse "hates to be clean," or tries to "ruin his coat," and seems to deliberately roll to "spite you for grooming him." The short answer to rolling when turned out is that it's normal horse grooming and social behavior to roll whenever turned out from the stall to an open area. But since rolling is one of the most interesting equine behaviors, I'll take the opportunity of your question to explain in greater detail how and why rolling is normal. In horses living outdoors all of the time, especially those living under natural herd conditions, rolling behavior is one of the most conspicuously frequent social and grooming behaviors. While we don't know precisely what stimulates rolling and what it means in all circumstances, it likely serves several purposes. These would include: Speed drying and refluffing of a wet or matted coat to restore maximum insulative properties. Covering the coat with dust that reflects the sun and possibly helps repel biting insects. Aiding in shedding. Increasing comfort by scratching. There are certain situations that seem to stimulate rolling, almost as if it is an automatic reflex. In wild and pastured herds, these could include approaching a common rolling area. Something about the site stimulates the behavior. Similarly, horses tend to roll at watering sites, and sometimes the water itself seems to stimulate the behavior. Also, rolling seems to be what is called "socially facilitated." Like yawning in people, rolling of one horse seems to stimulate rolling of a herd mate. This phenomenon is often quite conspicuous in young foals. Dad rolls, foal rolls, playmates roll, almost in a playful, mimicking fashion. Another strong social aspect to rolling is that it is a part of the ritualized inter-male behavior. This is very noticeable among bachelor bands. Pairs or small groups of males investigate one another, posture, stamp, and defecate in a stylized manner. These ongoing inter-male events often occur near the rolling site, and include "taking turns" rolling in a fixed order, either before or after the aggressive tiffs. As with defecating on stud piles, it often appears as if the top guy gets the last word; in other words, he goes last in order. Just like a pecking order for access to a small watering site, there is a fixed order of access to a dust bowl among members of a band, or bands within a herd. So when a band passes a rolling site, the members of the band will roll in the same order day after day. And if two bands pass by a rolling site at the same time, the dominant band always gets to use the site first. The two harem stallions might have a "conversation" over the rolling site. A very interesting phenomenon in horses is the "creation" of dust bowls at the rolling sites. Repeated rolling in the same spot serves to eliminate the vegetation and erodes the surface, forming a shallow bowl. With time the bowl has a very compacted base lined with fine powdery soil. The bowl also becomes "oiled" with body residues. The drier and hotter it gets in summer, the more rolling occurs, and the deeper and more compact and oiled the bowl becomes. When it rains, these dust bowls gather water and become temporary watering sites. It's tempting to attribute clever engineering skills to these animals as if they think it through. But this is a great example of an adaptive behavior-environment interaction that likely needs no cognitive thought on the part of the horses. Just one behavior to satisfy one need leads to serving other survival needs. Is there a relationship between feeding and rolling? In the environment where horses evolved, feeding is an ongoing activity day and night, so they don't have "meals" as we often provide them. Grazing occurs in long bouts of two or three hours interrupted by resting bouts. There does not appear to be an association of rolling with feeding. So I would guess that the fact that your horses roll when they are turned out is coincident with feeding, not related to feeding. A less common, but occasional question about rolling concerns horses which will try to roll under saddle. This is sometimes when they approach a stream, which is just natural behavior. Sometimes it seems related to discomfort from the tack.