There are many types of animal sporting events, with varying levels of participation from humans. Some are solely between the animals while others use the animals in a lesser role. Most sports involve training, while some can also involve selective breeding.
There are some large-scale events that include animals in a variety of sports. A rodeo can comprise many different sports, ranging from bull riding to pole bending.
Racing is the most popular form of animal-related sport, particularly horse racing. Some racing events directly involve humans as riders while others see the animals race alone. In some sports the rider is not directly riding the animal, instead being pulled along. Examples of this include harness racing, dogsled racing and popular ancient Greece and Roman Empire sport of chariot racing.
Greyhound racing, a popular form of animal racing, dates back to the 1800s in the United States, after the dogs were brought over from Europe to help control the hare population. While track racing is the most common, there are other forms of racing. Pigeon racing, for example, sees homing pigeons finding their way home from a set distance away. Kambala, he-buffalo racing in coastal Karnataka, India is a rural spectator racing conducted every year during winter in about 50 towns/villages. Racing events are a common way to gamble, with billions spent worldwide every year. This is one reason that some countries or states have made such sports illegal.
There are some non-racing competitive events involving animals. Polo is an example, with competitors hitting a ball with mallets while on horseback. Elephant polo dates back to the early 20th century when members of the British aristocracy in Nepal began playing the sport.