Body temperature and physical activity correlates of the menstrual cycle in Chacma Baboons (Papio hamadryas ursinus).

We investigated the temporal relationship between abdominal temperature, physical activity, perineal swelling, and urinary progesterone and estradiol concentrations over the menstrual cycle in unrestrained captive baboons. Using a miniature temperature-sensitive data logger surgically implanted in the abdominal cavity and an activity data logger implanted subcutaneously on the trunk, we measured, continuously over 6 months at 10-min intervals, abdominal temperature and physical activity patterns in four female adult baboons Papio hamadryas ursinus (12.9-19.9 kg), in cages in an indoor animal facility (22-25°C). We monitored menstrual bleeding and perineal swelling changes, and measured urinary progesterone and estradiol concentrations, daily for up to 6 months, to ascertain the stage and length of the menstrual cycle. The menstrual cycle was 36 ± 2 days (mean ± SD) long and the baboons exhibited cyclic changes in perineal swellings, abdominal temperature, physical activity, urinary progesterone, and estradiol concentrations over the cycle. Mean 24-hr abdominal temperature during the luteal phase was significantly higher than during the periovulatory phase (ANOVA, F((2, 9)) = 4.7; P = 0.04), but not different to that during the proliferative phase. Physical activity followed a similar pattern, with mean 24-hr physical activity almost twice as high in the luteal than in the periovulatory phase (ANOVA, P = 0.58; F((2, 12)) = 5.8). We have characterized correlates of the menstrual cycle in baboons and shown, for the first time, a rhythm of physical activity and abdominal temperature over the menstrual cycle, with a nadir of temperature and activity at ovulation.