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Dryad

Urine washing and urinary odor profiles in relation to dominance rank status in wild male capuchin monkeys (Cebus imitator)

Abstract

Urine plays an essential role in mammalian olfactory communication, though its potential role in primates has long been overlooked due to focus on their visual adaptations for communication. Here we combined behavioral and chemical data to test the role of urine in signaling male dominance in white-faced capuchins (Cebus imitator). We predicted that: 1) urine washing (i.e., depositing urine onto hands/feet and rubbing them onto substrates) is more frequently performed by alpha than subordinate males, and 2) the chemical composition of alpha male urine is distinct from that of subordinates. We collected 457 hours of focal behavioral follows and 153 urine samples from 24 males in five groups at Sector Santa Rosa, Área de Conservación Guanacaste, Costa Rica. We extracted urinary volatile compounds into thermal desorption tubes and analyzed them by gas chromatography-mass spectrometry. We found that alphas urine wash more than subordinates, especially during the dry season when urinary odors can last longer and intergroup interactions are more frequent. Additionally, dominance rank predicted a modest fraction of overall sample chemical dissimilarity. Our results support the hypothesis that urine may be an olfactory signaling medium; future experimental research is needed to test the extent to which urinary odors may be cues vs. evolved signals.