Urine washing in tufted capuchins (Cebus apella): relationship with air temperature and relative humidity in indoor and outdoor conditions

URINE WASHING IN TUFTED CAPUCHINS (CEBUS APELLA): RELATIONSHIP WITH AIR TEMPERATURE AND RELATIVE HUMIDITY IN INDOOR AND OUTDOOR CONDITIONS Urine washing behavior has been observed in many platyrrhine monkeys and some prosimians. Several functions have been attributed to it. In order to test a role of the urine washing in the regulation of body temperature - by means of evaporative cooling - the present study investigated the relationship between urine washing behavior and both air temperature (T) and relative humidity (H) in tufted capuchins (Cebus apella). Group scan sampling on five groups (N=43 animals) from 8 am to 6 pm provided 300 hours of data. The varying outdoor (N=21 animals) versus the constant indoor condition (N=22) allowed for the control of the T and H likely to influence a thermoregulatory response. Results revealed a strong relationship between urine washing frequency and both T (posi- tive correlation) and H (negative correlation) in the outdoor animals (p<.001), while no correlation was found for indoor animals. Both outdoor and indoor urine washing fre- quency showed a clear temporal pattern (p<.001) with a higher frequency around midday. In addition, individual urine washing frequency per hour increased as the group size increased. The presence of a temporal pattern during the day and the influence of the social environment in affecting urine washing occurrence, support the hypothesis that urine washing may have several functions over and above that of thermoregulation