The animal will lower his head and raise his hind quarters into the air and can also kick out with his hind legs (back), making it more powerful and difficult for the rider to stay on.
When the horse is loose in a field it is a natural expression of happiness.
The horse may be excited, fresh or just happy to be turned out.
Some horses are encouraged to behave this way for entertainment with the help of a strap around their flanks.
This is normal behaviour at rodeo events.
Bronc riding
This is a rodeo event that involves a rodeo participant riding on a horse (sometimes called a bronc or bronco), that attempts to throw or buck off the rider.
Horse bucking is encouraged and competitions are held and the winner is the rider who can stay on the longest.
A "flank strap" (or, "bucking strap") is used to encourage the horse to kick out straighter and higher when it bucks.
The flank strap is about 4 inches wide, is usually covered in sheepskin and fastens behind the widest part of the abdomen.
