Do horse and donkey belong to the same species?
No. Both belong to the family Equidae and the genus Equus, but they are different species – the domestic horse is Equus caballus, and the domestic donkey Equus asinus. The two can interbreed and produce mules (offspring of a male donkey and female horse) and hinnies (offspring of a male horse and female donkey), but these hybrids are nearly always sterile.