Urine-washing in white-faced capuchins: a new look at an old puzzle
Bibliographic record
Abstract
Some primates regularly wash their hands and feet with urine. This behaviour is outwardly similar to scent marking in other mammals, but it differs in that the urine is applied to the bare skin of the hands and feet rather than rubbed into the fur or applied directly onto an object in the environment. Empirical evidence for the functional significance of urine-washing remains inconsistent. We used rigorous statistical methods to examine environmental and social influences on urine-washing behaviour, using 4380 observation hours on five groups of wild white-faced capuchins (Cebus capucinus) in Costa Rica. Urine-washing frequencies were most strongly affected by environmental dryness, both within and between seasons, with markedly less urine-washing during humid conditions. Increased individual activity levels also promoted urine-washing. Among females, urine-washing was less frequent during lactation than during pregnancy and other reproductive states. Among males, urine-washing frequencies were greater in alpha males, who also exhibited a ‘vigorous’ form of urine-washing that may be functionally distinct. During the dry season, 3/5 groups exhibited more urine-washing than expected near fruit trees, but across groups there were no consistent spatial patterns for urine-washing with respect to water resources, home range overlap zones, core areas, inter-group encounter zones, and the home-range periphery. Urinewashing appears to differ fundamentally from common forms of mammalian scent marking. We suggest that its function is primarily mechanical, perhaps to apply a sticky residue to the hands and feet to improve grip on dry, arboreal substrates. Lesser signalling functions may include sexual signalling and resource labelling.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".