I recently purchased a
4-year-old gelding. He is extremely aggressive toward my other gelding
in the pasture, and I'm unable to turn them out together. I am able to
turn the horse out with my pony mare and pony gelding, but he
"herds" them constantly and often will unsheath his penis and
sustain an erection around mares. When left stalled, he exhibits other
strange behaviors such as constant stall weaving and defecating in his
water bucket. Please advise.
Let me start by saying that I have never
figured out defecating in water buckets. It happens; I've known several
horses which did it, both mares and stallions. In a male, you could
imagine it is some sort of marking behavior, since stallions in natural
social groups at liberty make stud piles near water holes. Maybe some of
our readers have some theories or tested explanations. In your gelding,
the defecating in the water buckets might or might not be related to the
other problematic behaviors.
The other behaviors you describe--the
herding of your gelding and mare, the aggression toward the other
gelding, and the sexual arousal around mares--all are probably related.
They represent stallion-like behavior. The weaving in the stall might
represent his thwarted stallion-like motivation to be out controlling
and protecting his herd. Or like the defecation in the bucket, it might
be coincidental. If he seems eager to get out of the stall (calling out
to the herd, hyperactive) the weaving likely is related to being left
behind from his herd that he urgently wants to protect and control, as a
harem stallion would.
So why does your gelding act like a
stallion? Occasionally, in evaluating geldings with behavior such as you
describe, we find that they are not completely castrated. That means
they might have some remaining testicular tissue, either a missed piece
of testicle or an abdominal testis (cryptorchid) that is producing male
hormones that drive the behavior. In fairness to the gelding, and before
you try to modify the behavior, I would recommend making sure that this
is not the case. The examination can be by your veterinarian with a
standard hormone challenge blood test. If there are positive baseline or
response levels of testicular hormones, then the tissue can be located
and surgically removed (sometimes easier said than done). When the
hormones diminish, the stallion-like behavior usually quiets
considerably, although not always. (For more on cryptorchids see The
of September 1999.)
What if the results are negative,
meaning that he is completely castrated, with no remaining testicular
hormones to drive this male behavior? Quite a few completely castrated
geldings with normally low steroid hormones continue to show
stallion-like behavior, particularly under pasture social conditions.
Estimates vary, but the percentage might be as high as 50% of geldings
which show considerable residual stallion-like behavior.
What can you do about it? You can
consider manipulating his social housing conditions to minimize the
behavior and/or the resulting problems. For example, you can house him
away from other horses all together. Geldings eventually quiet down
after prolonged separation from their "herd." You might
consider trying to take advantage of natural social suppression of
stallion-like behavior by housing your gelding within reasonable
proximity to one or more stallions. Most geldings become socially
submissive to stallions, and will appear to become demoted to the rank
of immature male or bachelor stallion.
The stallion-like behavior that occurs
in-hand or under saddle usually can be suppressed with behavior
modification similar to that which would be effective for those
behaviors in an intact stallion. We know that intact stallions can learn
when to "forget" their stallion behavior and take direction
from handlers and riders. Administration of the female hormone
progesterone sometimes can be a useful adjunct to the behavior
modification methods. It tends to suppress male-type behavior and add a
generally calming effect. Male-type behavior with herdmates in a pasture
usually is very difficult to suppress.
Please keep us posted on how things go.