Equus (genus) a female horse. With rare exceptions, these hybrids are sterile and cannot reproduce. A related hybrid, a hinny, is a cross between a male horse and a female donkey. Other hybrids include the zorse, a cross between a zebra and a horse and a zonkey or zedonk, a hybrid of a zebra and a donkey. In areas where Grévy's zebras are sympatric with plains zebras, fertile hybrids do occur. Equines have significant differences in size, though all are characterized by long heads and necks. Their slender legs support their weight on one digit (which evolved from the middle digits). Grévy's
Social groups in male and female prisons in the United States point. This difference is a manifestation of gendered social factors which influence male and female populations within prisons and within larger society. The populations and demographics of male and female inmate populations in the US are very different from one another. These differences factor heavily into theories on prisoner social organization. The most significant difference is in the relative size of male and female populations; in 2014 there were approximately 1,440,000 male and 112,000 female prisoners in the United States. The much larger size of the male prison population causes major differences in the institutions in which male and female