Effect of adult male sterilization on the behavior and social associations of a feral polygynous ungulate: the horse

Castration is commonly used to control the behavior of companion animals and livestock, yet there have been few longitudinal studies its effects. Despite ubiquity this surgery in ridden horses, effects castration (termed gelding horses) rarely examined a reproductive population. We tested on maintenance social behaviors individuals pre- post-gelding, comparison intact adult males (2 >16 years old) both harem bachelor status, we then how affected association with mares (i.e., group) compared controls, any associations. further explored foaling rate assess potential impacts population growth rate. conducted study over four (2017–2020) at two Herd Management Areas (HMAs) western Utah, USA: Conger Frisco. demographic observations year round HMAs record survival additionally recorded behavioral HMA. In December 2017, 27 from (42% population) were gelded returned range their groups. Due pre-treatment able compare stallions known status post-treatment (harem or bachelor), as well males. had no morbidity mortality related all maintained good body condition throughout study. There was effect (feeding, moving, standing). frequency agonistic behavior, non-significant tendency for less geldings; geldings showed more affiliative marking behavior. Age class and/or better predictors than gelding. Over time fewer harem, size declined during Horses that bachelors when tended remain bachelors, whereas same cohort mostly attained harem. Foaling reduced following treatment, but levels. From welfare perspective safe use feral horses has minimal horse interactions herd. Effectiveness would likely require larger proportion be castrated longer-term • impact (gelding) horses. concerns surgery. class/status Geldings lose harems 3 post-surgery. long-term reduction 42% gelded.