Final answer:
The organisms involved in this relationship are called mutualists.
Step-by-step explanation:
The organisms involved in this relationship are called mutualists. Mutualism is a type of symbiotic relationship where both organisms benefit. In this case, the oxpecker benefits by getting a meal from the pests on the rhino's back, and the rhino benefits by having the bothersome pests removed.
Learn more about Symbiotic relationships