Female ornaments: is red skin color attractive to males and related to condition in rhesus macaques?
Level 5 - mechanism / opinion, no new human data
Level 5 because this is non-human animal research.
PubMed 33814977 · doi:10.1093/beheco/araa121
What was done
Researchers analyzed digital facial photographs from 32 adult female rhesus macaques to quantify skin coloration. They measured male mating rates and consortship duration relative to female facial redness. They also tested for associations between coloration and indicators of physical condition (body mass index, skinfold fat) and physiological condition (urinary C-peptide and fecal glucocorticoid metabolite [fGCM] concentrations).
What was found
The abstract reports directional associations without numerical data, effect sizes, or statistical test values. Redder-faced females mated more frequently and were consorted for longer durations by top-ranked males. Redder females also had higher fGCM concentrations. Specific numerical relationships for skinfold fat, BMI, and urinary C-peptide were not reported in the abstract.
Why it matters
These findings provide evidence that interindividual variation in female primate coloration can function as a sexually selected ornament shaped by male mate choice in species with high reproductive synchrony.
Limits
The study is limited to an observational design in a small sample of 32 female rhesus macaques. The abstract provides no quantitative metrics, confidence intervals, or exact p-values. Causality cannot be determined, and the elevated glucocorticoid levels observed in redder females could reflect either metabolic costs or the stress of increased social and mating interactions rather than direct signaling mechanics.
Cited by
- supports In non-human animal species, facial reddening is associated with physical robustness.