Overview
- University of Cambridge researchers, in a study published Wednesday in Scientific Reports, documented regular geophagy, or soil‑eating, among Gibraltar’s Barbary macaques.
- Across 98 observation days from August 2022 to April 2024, the team logged 46 soil‑eating events by 44 individuals within a population of about 230 monkeys spread over eight groups.
- Soil‑eating was far more frequent in groups with heavy tourist contact, peaked during the summer tourist season, and was not seen in the only troop without access to human food, while junk food made up 18.8% of the macaques’ overall intake.
- The authors propose that clay‑rich soils may buffer stomach acidity, bind toxins, or help restore gut microbes after snacks like ice cream and crisps, though they stress that chemical and microbiome tests are still pending.
- Most incidents occurred in view of other macaques and troops showed distinct soil preferences—often red clay ‘terra rossa’ and, in one group, tar‑contaminated pothole material—supporting social learning and prompting renewed calls to enforce no‑feeding rules.