The stone handling behavior is a form of solitary object play. It consists in the versatile and non-instrumental manipulation of stones in a playful manner. This activity includes various behavioral patterns, such as gathering several stones into a pile, clacking two stones together, or repeatedly pounding a stone on a substrate (Huffman, 1984).

Currently, 45 different stone handling patterns are documented in Japanese macaques [REPORT]

(see photos).

Among them:

• Carry: Carry a stone cuddled in hand from one place to another (photo)
• Cuddle: Take hold of, grab or cradle a stone against the chest (photo 1 and 2)
• Gather: Gather stones into a pile in front of oneself (photo)
• Grasp with hands: Clutch a stone or a pile of stones gathered and placed in front of oneself (photo)
• Move and push/pull: Push/pull a stone with one or both hands while walking forward/backward (photo)
• Scatter: Scatter stones about, on a substrate, in front of oneself (photo)
• Rub with hands: Hold a stone in one hand and rub it with the other (like potato-washing) (photo)
• Rub stones together: Hold one stone in each hand and rub the two stones together (photo)
  
  

Stone handling is mainly a solitary activity, but occasionally, it can be integrated into social interactions, such as social play (see photo) and grooming (see photo).

The acquisition of stone handling in infants is strongly influenced by the relative amount of time spent in proximity to their mothers as stone handling models (see photo).

Stone handling is one of the longest studied and best-documented cultural behavior in monkeys to date [BOOK CHAPTER]