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
Extended female sexuality males. According to Hrdy's hypothesis, extended female sexuality is an adaptive process with an aim of creating paternity confusion in their male counterparts. Paternity confusion refers to the male being unsure as to whether offspring are genetically his own. If the female mates with different males (at all points of her ovarian cycle) whilst concealing fertility, then the males will inevitably have paternity confusion. Paternity confusion is proposed to be an adaptive function for preventing infanticide. Thus, if the female can successfully create paternity confusion, males will be less likely to kill her offspring, as the lack of paternity certainty