Meeting Abstract
Primate field metabolic rate (FMR) is low compared to non-primate eutherian mammals, with primates using less energy than expected for their body masses. The prevailing hypothesis is that lower-than-expected primate FMR reflects a metabolic adaptation for a low-throughput life history strategy. We propose an alternative hypothesis: that high ambient temperatures constrain primate FMR in a similar manner to other mammals that inhabit high ambient temperature environments . To test this hypothesis, we used a simple thermodynamic model for FMR similar to Speakman and Krol (2010). We predicted that FMR would scale to body mass (MB) to the same exponent as surface area (AS) and that remaining FMR variation would negatively correlate with mean ambient temperature (Ta). We tested the predictions using FMR, AS, and Ta data from the literature and also tested the relationships between basal metabolic rate (BMR) with MB and Ta. Both phylogenetically-informed and uninformed regressions produced the same results: FMR, BMR, and AS all scale to MB with the same general exponent of 0.70-0.72. As predicted, residual FMR variation showed a negative relationship with Ta. After accounting for MB and Ta, primate FMR fit the general mammal prediction. Interestingly, residual BMR variation also had a negative relationship with Ta, which we interpret as a mechanism for maintaining metabolic scope (FMR/BMR) in the face of decreased FMR in warm environments.
