When a horse breeds with a donkey, the result is a hybrid offspring called a mule. If a female horse (mare) mates with a male donkey (jack), the offspring is called a mule; if a male horse (stallion) mates with a female donkey (jenny), the offspring is called a hinny. Mules and hinnies are known for their endurance, strength, and intelligence, but they are also usually infertile, which means they cannot reproduce.