Thyroid hormone fluctuations indicate a thermoregulatory function in both a tropical (Alouatta palliata) and seasonally cold ‐habitat (Macaca fuscata) primate

Thyroid hormones boost animals’ basal metabolic rate and represent an important thermoregulatory pathway for mammals that face cold temperatures. Whereas the cold thermal pressures experienced by primates in seasonal habitats at high latitudes and elevations are often apparent, tropical habitats also display distinct wet and dry seasons with modest changes in thermal environment. We assessed seasonal and temperature‐related changes in thyroid hormone levels for two primate species in disparate thermal environments, tropical mantled howlers (Alouatta palliata), and seasonally cold‐habitat Japanese macaques (Macaca fuscata). We collected urine and feces from animals and used ELISA to quantify levels of the thyroid hormone triiodothyronine (fT3). For both species, fT3 levels were significantly higher during the cooler season (wet/winter), consistent with a thermoregulatory role. Likewise, both species displayed greater temperature deficits (i.e., the degree to which animals warm their body temperature relative to ambient) during the cooler season, indicating greater thermoregulatory pressures during this time. Independently of season, Japanese macaques displayed increasing fT3 levels with decreasing recently experienced maximum temperatures, but no relationship between fT3 and recently experienced minimum temperatures. Howlers increased fT3 levels as recently experienced minimum temperatures decreased, although demonstrated the opposite relationship with maximum temperatur...
Source: American Journal of Primatology - Category: Psychiatry & Psychology Authors: Tags: RESEARCH ARTICLE Source Type: research