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
Cryptic female choice in which a male's interaction with a female is of detriment to her personal well-being and that of her offspring, one such situation occurs when a male harasses a female prior to copulation. In such circumstances where the female's lifespan and fertility are compromised, it benefits females to develop evasive mechanisms. In addition, in some species where multiple males inseminate a female, a female is able to select the most desirable sperm for her offspring by rejecting that which she desires less. In both of the aforementioned situations it is a female's reproductive actions that affect male reproductive success following