Read the following context and answer the question.
Context: James , in a fit of laughter slapped Artie 's back , and for some reason , this caused Artie 's head to randomly explode . James stopped laughing and turned to look when his horse suddenly reached up , with its neck stretching to accommodate its actions , and bit off James ' head . Both human bodies then fell off their horses , only to sink like bricks in quicksand in a pile of horse manure .
Question: Where were James and Artie when James slapped Artie on the back ?
Answer:


They were riding their horses .