When two animals of a different species mate, they are usually too genetically different to produce an offspring. If the two species are genetically similar, they may be able to produce a hybrid offspring, such as when a horse and a donkey breed and create a mule.
Interspecies mating is well-documented and not uncommon, with examples being found throughout the world. For example, when a zebra breeds with a horse, it produces a "zorse," and when a lion breeds with a tiger, it produces a liger (if the lion is male) or a tigon (if the lion is female). Most interspecies offspring are infertile and unable to continue their lineage, but a "wholphin," a mix between a dolphin and a killer wale, born in 1985 at Sea Life Park Oahu, Hawaii was able to give birth to a calf in 2004.
Interspecies mating occurs even when there is no possibility of an offspring. On Marion Island, a remote nature reserve in the Southern Indian Ocean, an Antarctic fur seal was observed trying to mate with a king penguin. This phenomenon is known as misdirected mating and has also been observed in sea lions, sea otters, and many species of bird, insect and fish.