Meeting Abstract

P3.216  Sunday, Jan. 6  Too hot, too cold, or just right: thermal challenges facing mantled howling monkeys (Alouatta palliata) in a dry tropical forest THOMPSON, CL*; WILLIAMS, SH; GLANDER, KW; TEAFORD, M; VINYARD, CJ; NEOMED; Ohio University; Duke University; High Point University; NEOMED cthompson@neomed.edu

Free-ranging mammals are confronted with the challenge of maintaining an energetically neutral body temperature within a thermally dynamic environment that changes daily, seasonally, and annually. While many laboratory studies have been conducted on primate thermoregulation, we know comparatively little about the thermal pressures primates face in their natural, evolutionarily-relevant environment. We examined thermoregulation of free-ranging mantled howling monkeys in a lowland tropical dry forest in Guanacaste province, Costa Rica. We recorded subcutaneous (T_sc) and near-animal ambient temperature (T_a) from 11 animals at 10 min intervals over 1606 sample hours. We found significant positive daily cross-correlations between T_a and T_sc (average r=0.70±0.17) with a modal (44% of days) lag time <10 min. T_sc increased with higher T_a, but plateaued at T_a>41°C. Similarly 95% of dry season cases with T_a>T_sc occurred at T_a>38.1°C, which implies that howlers use a cooling response to prevent rising temperatures over a threshold T_a. However, this cooling response was relatively infrequent, with T_sc being below T_a in only 14% of dry and <1% of wet season samples. The magnitude of cool vs. warm stress differed as well, showing a maximum deviation of 4.8°C when T_a>T_sc, vs. 15.4°C when T_a<T_sc. Our data support a hypothesis that, despite inhabiting a dry tropical environment, howling monkeys experience more ‘cool’ than ‘heat’ stress. This suggests that cool temperatures may be a prevalent thermoregulatory challenge for primates, particularly smaller primates living at higher latitudes and/or altitudes. Support: NSF, OU Baker Award, DU A&S Council.