It's a beautiful winter weekend, and
finally you have a full morning to spend at the barn. You're happily
grooming your horse when you notice a cluster of patches of wet hair on
his side. Peculiar pattern to the wet hairs -- all are lying forward as
if combed with a wet brush. Oh well, odd but probably nothing, you
think. But wait, some of the wet spots have hairs missing or chopped off
bluntly. You check the other side, and there you find some more patches,
like the wet ones, but as if they have now dried. What's going on? There
are more of these patches on the left side than on the right side, but
they all are in the same area of the abdomen, from the ribs to the
Just then the barn manager comes in all
excited. She's glad you're there early today, because when she was
feeding this morning, she found your horse spinning in his stall,
tearing at his blanket and biting at his sides. Her first reaction was
to scream at him to stop--and he did. She figured the blanket was the
problem, maybe it was rubbing or pinching him under the leg. She got
some help to investigate. They couldn't find anything out of order with
the straps or the blanket, but took it off anyway. Then, just as they
closed the stall door, he really went nuts, spinning in a very tight
circle, biting his left flank. With each bite, he squealed and kicked
out. As he was turning and nipping, he sometimes was bucking and
squealing. They were too scared to open the door. He went on for what
seemed like forever, as if he wouldn't stop until he tore up the stall
or killed himself. Then he gradually came out of it.
"When we screamed his name, he
turned toward the stall door, looking at us with a sort of a worried,
glassy eye, like he didn't know what was happening. We threw him his
hay, and he's been pretty quiet since."
You run your fingers over the wet areas
on his flanks and feel some crusty bumps on the underlying skin.
Separating the hairs, you can feel little marks in the skin -- anywhere
from one-quarter to one inch in diameter. Some are fresh nicks, some are
scabbed over, some look healed. The rest of his coat is unblemished. No
marks, no wet spots, no chopped or missing clumps of hair other than on
his flanks and over his ribs.
So what is going on here?
This behavior commonly is called flank
biting or flank sucking. The biting is one aspect of a cluster of
behaviors called self-mutilation, because the horse likely will incur
serious self-injury during these explosive episodes.
In addition to biting the flanks,
self-mutilation sequences can include seemingly uncontrollable violent
behavior. From horse to horse, the sequence and form can vary, but most
typically includes spinning in circles, bucking, and kicking out with
one or both back legs while nipping at the flank, shoulders, or chest.
In the photos at the bottom of page 76, there is an example of a horse
biting more violently at his chest, and a resulting chest avulsion.
In extreme cases, the horse can
violently lunge its body or head into a wall or other solid object. More
rarely, a horse might "throw itself" to the ground (from
standing to lateral recumbency). A single episode can last from a few
seconds to several minutes, uninterrupted. The horse can work up a
lather and steam in cool weather. Episodes usually occur in a series
separated by a few seconds to a few minutes over a period of minutes, to
hours. The total daily time spent self-mutilating can vary from a few
seconds to an hour or more. In addition to bite wounds, the most common
injuries are to the legs and feet from the spinning and kicking.
Self-mutilation behavior of one form or
another has been described in many different species, including humans.
Dog and cats lick and chew on their paws or tails. People do all sorts
of things--pull out their hair, bite their fingernails or lips, scratch
themselves, or deliberately inflict burns, cuts, or other wounds.
People who have seen a horse in the
midst of attacking itself often describe the episodes as the most
bizarre animal behavior they ever have seen. Mental health professionals
or others with first-hand experience with human psychopathology often
ask whether this might be the horse equivalent of severe neurotic or
even truly psychotic behavior seen in people. For example, Dr. Nicholas
Dodman, a veterinary animal behavior specialist at Tufts New England
Veterinary College, said he has wondered whether certain forms of
self-mutilation in horses might be similar to Tourette's Syndrome in
humans. There are some interesting similarities, and some clear
Since self-mutilation occurs in other
animal species and a variety of human psychopathologic syndromes, it's
probably too early to conclude that any of the self-mutilation seen in
horses represents the same pathology as Tourette's in people. In other
species, the trend in clinical veterinary behavior has been to label
self-mutilative behavior "obsessive-compulsive disorder," or
This syndrome in humans has two distinct
components. One component is the compulsive, repetitive behavior, such
as repeatedly checking to see if the stove has been left on. The other
component is the accompanying obsessive thoughts or worries, such as
concerns about being caught in a burning building. Often the thoughts or
worries are related to the compulsive behavior and logically appear to
In the case of animals, we don't know
whether they think or worry, so this label of obsessive-compulsive
behavior might be too elaborate. Some behaviorists now are calling these
behaviors in animals simply compulsive behavior.
There are at least three distinct types
of self-mutilative behavior in horses. One type is simply an
"extreme" behavioral response to physical discomfort. We know
that physical pain alone, particularly in the abdominal area, can evoke
behavior similar to that of the horse in the situation described above.
We know it is physical pain because coincident with finding and
correcting an apparently or potentially painful condition, the self-mutilative
behavior stops without any other treatment. For example, the classic
behavior we associate with colic or early labor in broodmares involves
turning the head back toward the flank, either looking or nipping at the
flank, and sometimes kicking out. Although it is not as common, some
horses' behavioral response to physical pain has more violent episodes,
including spinning, kicking, bucking, and serious self- biting. Some of
the less-common physical root causes for violently colic-like behavior
have been a twisted testicular cord, an abdominal abscess, urethral
tears, or gastric ulcers. These sometimes can be intermittent and
difficult to find. This is in contrast to the other types of
self-mutilation. When there is a physical cause, there often is an
increase in the behavior in association with work. The most explosive
episodes might be during or soon after work. As time goes on, the horse
might anticipate the exacerbation of pain with work, so can become
agitated when being prepared for work.
A second type of self-mutilation is what
could be called self-directed intermale aggression. This type occurs in
stallions and geldings. The sequence follows what two stallions at
liberty would do when meeting, except that the stallion himself is the
target of his own behavior. When stallions meet, they typically stand
parallel to one another, head-to-tail. They investigate each other's
flank area, usually sniffing and nipping at the flank and genitals. The
encounter can be pretty noisy. The stallions usually squeal and kick out
with each nip or bite. They also might spin, buck, stomp, and romp,
going around one another in circles. The sniffing of each other's flank
and genitals, and of each other's feces, is an important trigger for the
nipping and biting.
Sometimes the self-mutilation process
begins over a stud pile. In the stallion which is sniffing and biting
himself, each episode begins with the sniffing of his own feces or feces
of other stallions in shared turn-out facilities. Oily body residues on
stall walls, fences, or doorways can trigger episodes. We have seen
several cases of self-mutilation that appeared to have started when a
stallion was exposed to the smelly residues of another stallion in a
Unlike the pain-related self-mutilation,
this type usually develops over a period of months. It can start as
early as the first year of life or as late as the teens. It typically
continues for the life of the stallion.
A third type of self-mutilation is a
more quiet, rhythmic, repetitive nipping at various areas of the body.
It looks similar to stereotypic weaving or stall walking in that it
appears that the horse has nothing better to do. By formal definition,
stereotypic behavior is characterized by repetitive, highly stylized,
and seemingly functionless movements and sequences of movements.
Spanning the top of pages 76 and 77 is a
series of photos of a stallion which had a very fixed pattern of biting
himself from flank to shoulder to chest to opposite shoulder to opposite
flank and on and on. He did it at the same place in the pasture at the
same time of day for the same length of time, just as some horses walk
their stall in very complex and fixed patterns day after day.
Stereotypies occur in one form or
another in all captive wild and domestic animal species, and are a
common feature of human psychopathology, as well as developmental and
neurologic disorders. Subadequate environment and nutrition seem to be
the major factors predisposing animals to stereotypies.
In horses, the classic stereotypies are
cribbing, weaving, pacing, stall-circling, and head-shaking. Certainly,
in cases in which a physical root cause is not apparent, self-mutilation
fits this definition of a stereotypy. Of course, the performance of a
stereotypy, no matter what the initial precipitating cause, is
self-rewarding. Endorphins are released, and they can be positive
reinforcement sufficient to sustain the behavior as a habit. We often
wonder if self-mutilation, for which we can find no contemporary
physical cause and that doesn't quite fit the self-directed intermale
aggression type, might have started during a period of physical
discomfort, but now is a lingering habit.
How Common Is Self-Mutilation?
It's very difficult to estimate how many
horses suffer from self-mutilation. My guess would be that the problem
occurs in less than 0.005% of all horses. Most equine veterinarians
might see only a few cases in their entire careers. Self-mutilation can
occur in stallions, mares, and geldings. Of course, the self-directed
intermale aggression type is almost always in stallions and geldings. We
don't know whether or not the predisposition for self-mutilation is
highly heritable. We know that the behavior probably is the result of
domestic environmental and nutritional factors, in that it apparently
does not occur in wild or feral horses.
Where Does It Hurt?
For those horses whose self-mutilation
episodes looks like a violent form of colic, it is critical to look for
and immediately treat any possible causes of discomfort. Except for
classic colic, this often is easier said than done. It sometimes can be
tough to find (see the boxed table of examples of possible physical
causes of discomfort on page 74). No matter what the slickest animal
psychic would have us believe, our animals, like human infants, have
only their non-verbal behavior as clues to tell us where they hurt.
After years of losing sleep trying to find causes of self-mutilation in
horses, I think our best hope for figuring out potential physical
sources of discomfort that might be provoking episodes of
self-mutilation turns out to be pretty inexpensive and very low tech. It
is simply to critically observe the horse for hours at a time. This can
be done live, but there are many advantages to video recording the
Long, continuous observation periods
allow the horse to go back to its ongoing behavior, as opposed to being
distracted by human presence. Long observation periods also will enable
you to see how the self-mutilation episodes start and stop, and what in
the environment might provoke them. When casually watching a
self-mutilating horse, your attention is drawn to the noisy, more
violent episodes. When watching the horse continually for hours, you
likely will see mild and violent episodes. The milder episodes
often are more useful than the explosive episodes in localizing
potential sites of discomfort.
Once you have a clue as to where the
pain might be, you can be aggressive with veterinary diagnostics. This
might include classic radiography, scintigraphy, endoscopy, and
Even if it appears to be a classic
stereotypy, or a psychological behavior problem, we should never stop
looking for a possible physical cause. A great example illustrating this
point in horses is the case of head shaking behavior. For many years,
veterinarians have looked for possible sources of discomfort in cases of
head shaking. Many times a source could be found--things like ear mites,
tooth abcess, guttural pouch problems, or allergies. But many times,
nothing physical could be found and it was assumed that the problem was
psychological. Only a few years ago did scientists in the United Kingdom
and California find that some headshaking in horses appears to be
induced by bright light or loud sound. It is a real physical problem
involving hyperactivation of a nerve tract that is physically irritating
to the horse. (See The Horse of October 1996, page 70.)
What Else Can You Do?
The best outcome of immediate and
aggressive veterinary evaluation is to identify and quickly treat a
physical cause. An equine behavior specialist can be a valuable member
of a veterinary team. By evaluating the behavior, possible sites of
discomfort can be identified, and an opinion can be offered on primary
or secondary psychological components to the episodes. If physical
discomfort is eliminated, the self-mutilation typically stops almost
immediately. We have seen cases in which months or years passed before a
root physical cause was found, in which the self-mutilation stopped
immediately when the discomfort was alleviated.
Unfortunately, often a physical cause is
not found and the conclusion is drawn that this is the self-directed
intermale aggression type, or is simply a stereotypy. Over the years,
mostly by trial-and-error, we have found a number of different treatment
approaches, each of which typically is either helpful, or at least does
not exacerbate the self-mutilation. Most are simple management changes
that seem to work by distracting the animal to another activity; some
involve sophisticated pharmacology.
Traditionally, a large percentage of the effort, thought, and expense of
treatment of self-mutilation has involved various methods of physically
preventing or discouraging the behavior. This often is the first thing
you will want to consider while further evaluation is organized. Special
neck cradles and side poles, grazing muzzles, bibs, and protective wraps
and blankets can be used to prevent injury. Physical restraint alone
rarely "cures" self-mutilation. All too often when the horse
is effectively restrained from performing one behavior, another problem
behavior develops. If biting is prevented, the horse might start kicking
or lunging into walls. In the short term, while looking for and treating
possible causes, it is wise to creatively work at keeping the animal
from further injury.
For any restraint, care must to taken in
devising materials that don't cause new rub sores or other irritations.
My favorite of all the restraints for self-biting is the grazing basket
shown on page 78. The horse effectively can eat hay and grass through
the openings. The basket inhibits a substantial grab of flesh, although
the persistent horse still can work a small nip of hair or skin through
the basket openings.
Social, feeding, and work
distractions Typically, the most effective management changes
are those that seem to provide motivation for a substitute behavior or a
strong distraction to focus on something else. For a stallion,
self-mutilation sometimes can be relieved significantly if the stallion
is turned out to live in a large pasture with one or more mares. In that
situation, the stallion becomes a harem stallion with great
responsibility to herd and defend the mares. Those harem maintenance
behaviors seem to occupy the stallion's time and distract him from the
problem behavior. If he is not supplemented with concentrated feed, his
grazing and resting fully occupy the remainder of his time.
Of course, this often is not a plausible
solution for the fancy breeding or busy performing stallion. There might
be some difficulty and danger in taking such a stallion or his mares in
and out of such a situation. Most stallions will not want to leave their
mares. But to the extent that the stallion can be distracted socially,
in some cases it is worth trying.
Horses appear to find meaningful social
companionship from animals of other species. Donkeys, goats, rabbits,
and even chickens are useful as stall or pasture companions. In my
experience with chickens as stall companions for self-mutilators, it
seems that the horse sometimes is reluctant to move around the stall,
lest it cause the chicken to scurry and flutter. Some stallions also
seem distracted by their effort to avoid stepping on the chicken.
Another effective distraction for many
self-mutilators is a vigorous appetite. A change in diet from one heavy
with grain to one of grass and grass hay only (without any grain or
richer forage) often can lead to a remarkable change in behavior. The
horse might spend almost all of its time eating and resting, with
seemingly no time for anything else, including self-mutilation. A
grazing muzzle like the one described earlier can effectively prolong
the eating time.
The all-grass, no-grain diet might have
other benefits for behavior. We know from work in horses and other
grazing species that grain diets predispose an animal to stereotypies
and other behavior problems. The grain diet might alter the brain
neurochemistry, setting the animal up for developing abnormal behavior.
We long have appreciated that grain increases the risk of behavior
problems and high-forage diets reduce the risk of behavior problems.
Work For the
self-directed intermale aggression type of self-mutilation, the behavior
seldom is seen during work. Moderate work also stimulates appetite. A
horse which works one to two hours a day and which is fed ad lib grass
and grass hay almost always will spend 60% or more of his time eating
and 20% of his time resting. This approaches the natural time budget of
a horse at liberty or in the wild. Breeding work sometimes reduces and
sometimes increases the frequency and intensity of self-mutilation.
Gelding stallions? For
the self-directed intermale aggression type self-mutilating stallions,
some veterinarians recommend castration, and in some cases it works very
well. Unfortunately, it also can get worse or won't change. When
advising clients on this option, I always am reminded of the dozen or so
geldings we have known which seemed normal as colts, but were first seen
to self-mutilate soon after castration.
Pharmacologic aids, which in some cases have appeared helpful in
relieving self-mutilation, include long-acting tranquilizers, tricyclic
anti-depressants such as imipramine and clomipramine, progesterone, and
the nutritional supplement l-tryptophan. Some of these have been
discovered by accident and some are based on theories of brain
neurochemistry. None of these medications alone or in combination is
likely to eliminate self-mutilation completely. The particular choice
depends on the severity and nature of the self-mutilation. In
combination with management changes, medications often are judged to be
valuable parts of the plan to eliminate self-mutilation. The tendency is
for people to over-estimate their potential. An important concern for
clinicians who medicate the horse early in the evaluation is that the
drugs might help a horse to cope with physical discomfort, thus could
effectively mask the symptoms and delay diagnosis of a treatable
Other treatment tips For
horses whose self-mutilation seems to be triggered by male odors and
feces, any number of creative steps can be taken to reduce the
stimulation. Odor-masking preparations can be applied to the nostrils,
the horse can be bathed frequently, and feces and oily residues can be
removed from stalls and pastures. Sometimes, the sight or smell of
another stallion seems to provoke episodes. Housing changes can reduce
the frequency and severity of self-mutilation.
In our clinic we find that long-term
video surveillance of the horse can reveal events and situations that
provoke the behavior. Often these "provokers" can be simply
and inexpensively eliminated. For example, occasionally you find a horse
which only bites himself when the feed cart is coming down the aisle, or
when other stallions are on their way to the breeding shed.
Tie-stalls For reasons
I'm not sure we ever will understand, simply housing a horse in a
tie-stall can effectively eliminate self-mutilation. Recent work with
tie-stalled horses in the pregnant mare urine industry has indicated
that abnormal behavior in general is very low in tie-stalled horses
compared to box-stalled horses.
No one treatment alone is likely to be
effective. The cases for which the greatest relief has been achieved
have involved simultaneously implementing as many of the treatment steps
as possible. We recommend spending time with your veterinarian to
develop a custom plan based on everything you know about the horse. Once
everything is organized, we recommend implementing all the changes and
treatments at once. This is not good science in that you might never
know which of the changes were most effective, but experience has taught
us that major change often is more effective than a systematic,
In summary, we really know very little
about the causes of self-mutilation, other than physical discomfort. It
is important to realize that except for those cases for which a physical
discomfort can be identified and eliminated, the self-mutilation likely
will never be cured. The current treatments for the self-directed
intermale aggression and stereotypy types of self-mutilation rarely
effect a cure. At best, diligent attention and care will keep the levels
of injury low.