Spontaneous erection and masturbation in equids

S. M. McDonnell, M. Henry* and F. Bristol†

University of Pennsylvania School of Veterinary Medicine.
Hofmann Center for Reproduction Research, New Bolton Center
Kennett Square, Pennsylvania 19348. U.SA,
*School of Veterinary Medicine, University of Minas Gerais
Cp 567.31310 - Belo Horizonte, Brazil 
Western College of Veterinary Medicine
University of Saskatchewan
Saskatoon, Saskatchewan S7N OWO. Canada


    Spontaneous erection accompanied by ‘masturbation’ occurs in equids. Spontaneous erection involves extension of the penis from the prepuce with engorgement to its full length and rigidity, in a non-sexual context. Masturbation involves rhythmic bouncing, pressing or sliding of the erect penis against the abdomen achieved by rhythmic contraction of the ischiocavernosus muscles and/or pelvic thrusting. The significance and regulation of these behaviours are not well understood. Spontaneous erection and masturbation in equids have been viewed traditionally as aberrant behaviours resulting from regimentation or restricted activity of captive or domestic existence or, alternatively, a ‘venting’ of sexual frustration, either from inherent hypersexuality or from thwarted access to heterosexual activity. Often it is assumed that masturbation limits the potential fertility of a stallion by depleting sperm reserves and sexual energy. This report summarizes a series of studies of spontaneous erection and masturbation in equids in a number of different management and breeding environments.