In any of the equine behavior literature that I have read, I am unable to find any description of the sleeping behavior we see in our retired broodmare (17 years old). She has functioned as the watch horse in the small herd she was from, and she now is retired at our two-horse farm and continues to maintain that role. She is rarely seen lying down, nor shows evidence of that–no surface dirt or shavings in her coat. She does not prefer to rest inside the run-in barn stall (if she does, it is always with her head facing out), but is often seen sleeping standing up just outside of the barn and stall door of the second horse as he sleeps lying down inside.
Often I have seen her resting, head drooping lower and lower over straight parallel forelegs (with a rear leg cocked in relaxation fashion). However, sometimes after a few minutes of what appears to be deeper sleep, her forelegs begin to buckle at the pastern and knee joints. As she begins to go down, she wakes up in a sudden jerking motion, lifting her head, then all is fine. However, I have suspected that she falls occasionally onto a foreleg during times of sleep as evidenced by dirt or shavings only on the anterior surface of a knee, the cannon bone area, and the long pastern. The opposite leg has excess dirt or shavings over the long pastern area.
She is often very grumpy when touched in the shoulder and chest area. (Is she sore?) This behavior has been attributed to past experience with saddling, but the ears back and half-hearted nip directed to the handlers approaching a hand or light touch at that area occurs with or without the presence of a saddle or saddle-related human behaviors (placing riding equipment and grooming supplies, positioning, etc.). Through clicker training she has substituted a head down response for the nip action, most of the time.