Pickle barrels as enrichment objects for rhesus macaques

Area of Science:

• Primate behavior
• Animal enrichment
• Ethology

Background:

• Rhesus monkeys (Macaca mulatta) are a common model species in biomedical research.
• Enrichment strategies are crucial for maintaining psychological well-being in captive primates.
• Understanding social dynamics and object interaction is key to effective environmental enrichment.

Purpose of the Study:

• To investigate the impact of pickle barrels as an enrichment object on the behavior of rhesus monkeys.
• To compare affiliative and agonistic behaviors between rhesus monkeys in an enriched environment and a control group.
• To determine patterns of pickle barrel usage across different age and sex classes.

Main Methods:

• Observation of two breeding groups of rhesus monkeys in outdoor enclosures over 84 hours.
• Utilized instantaneous scan sampling of focal animals to record behaviors and barrel interactions.
• Categorized behaviors (agonistic, affiliative, grooming) and barrel use (type, arrangement).

Main Results:

• Animals in the enriched environment showed significantly higher rates of affiliative contact (60.8%) and social grooming (62.2%).
• Pickle barrels, particularly swivel and stationary types, were frequently used (55% of scans).
• Yearlings, juvenile females, and old males exhibited disproportionately high barrel usage (82.8% of scans).

Conclusions:

• Pickle barrels serve as effective enrichment objects for rhesus monkeys, promoting positive social interactions.
• Enrichment via pickle barrels benefits younger and older individuals across both sexes.
• Differential usage patterns suggest specific age/sex classes derive greater utility from this enrichment.