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 gangs, which are initially formed to provide protection to their members, as these members can no longer rely on norms or correctional officials to do the same. While homosexual contact is common in both male and female prisoners, female inmates tend to emphasize an emotional connection, sometimes displaying affection without any intention of sexual contact, male inmates tend not to display any affection despite frequent sexual interaction. This phenomenon is caused partially by the extreme stigmatization of homosexuality in male prison populations. Prison conditions encourage young male inmates to emphasize their masculinity, causing participants in homosexual relationships typically explain their