Urine washing is a common behavior in strepsirrhine and platyrrhine primates, but its function is still poorly understood. We investigated the factors influencing urine washing behavior in 2 captive groups of tufted capuchins (Cebus apella). Urine washing was affected by group membership (subjects in the 2 groups urine washed at different rates) and was negatively related to age, but was not influenced by sex or dominance rank. Females urine washed less when in estrus, and the presence of an estrous female did not affect male urine washing behavior. We observed independent effects of diurnal and climatic variables on urine washing. Tufted capuchins urine washed more at midday and under conditions of higher temperatures and lower relative humidity. Both of the latter effects were evident only at the lowest temperatures (5-20°C). Our results indicate that urine washing is sensitive to multiple influences, and that hypothetical communicative or thermoregulatory functions do not fully account for its occurrence.
