Mule

A Mule is a cross between a male donkey and a female horse. Because donkeys and horses have differing chromosome numbers, Mules rarely produce offspring and are usually sterile. They are less susceptible to the rain and sun because their skin is thicker than horse skin. Following the American Revolution, they grew in popularity as working animals. On average, a mule can carry 20 percent of its body weight and live on average for 30-50 years.