Stallions are commonly known to be feisty, fresh, and sometimes difficult to handle, largely attributable to the testosterone coursing through their bodies. But when mares begin to display aggressive or stallionlike behavior, the reason for the atypical behavior can be less obvious.

At the 2010 American Association of Equine Practitioners Convention, held Dec. 4-8 in Baltimore, Md., Monica Morganti, DVM, aa resident in veterinary medicine at the University of California, Davis, presented a study in which she examined the role the adrenal glands play in causing mares to exhibit stallionlike behavior.

The stallionlike behaviors that mares sometimes exhibit include stallionlike vocalizations, aggressive attitudes towards handlers and other horses, and regular performance of the flehman response. These mares may also have an elevated testosterone level.

Along with a team of colleagues, Morganti set out to determine if the adrenal glands have an effect on the testosterone level in mares that display stallionlike behavior