Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
Social groups in male and female prisons in the United States Southwest. She found that officers consistently expressed a preference to work in men's prisons, citing differences between male and female inmates as the main cause; officers perceive female inmates to be more difficult to manage, more likely to question an instruction, and less respectful than males. Many respondents also characterized female inmates as more emotional and therefore more likely to become inexplicably violent, while male violence is rationalized as having understandable goals. In this way, female violence is seen as irrational and ineffective whereas male violence is seen as meaningful and understandable. Britton notes that these perceptions seemed to be