Gorilla bones

Large monkey bones (called Monkey bones in-game) are used to train the Prayer skill. These are dropped by Monkey Guards and gives 18 or 20 Prayer Experience when buried. They can be exchanged during and after the Monkey Madness quest for a Gorilla greegree. The two types of Monkey Guards (bearded and unbearded) drop different bones that give different amounts of prayer experience, and are considered different items.