Body Temperatures in Dinosaurs: What Can Growth Curves Tell Us?
Figure 4
Results of the sensitivity analysis on the influence of values assumed for g0, the scaling exponent of MGR, and the activation energy term e0.1Tb on estimated Tb,MGR of extant (non-avian) reptilian and mammalian species.
For different body masses (1, 10, 100, 1000 kg), Tb,MGR was calculated from the MGR-Tb-equation in Gillooly et al. [4] applying the MGR-regression for reptiles (blue) and mammals (red), respectively to estimate MGR from body mass (Table 1). Tested parameter values: (A) in the MGR-Tb-equation g0 was set to 0.00017 (reptiles [4]), 0.0002 (average of reptiles and mammals [4]) and 0.00023 (mammals [4]); (B) scaling exponent used in the MGR-Tb-equation was 0.65, 0.75 (default) and 0.85; (C) 0.075, 0.1 and 0.15 was used as an exponent in the activation energy terme0.1Tb, or an activation energy of 0.447, 0.65 and 0.894 eV, respectively. The average values used by Gillooly et al. [4] result in average Tb,MGR for reptiles (open dots) and mammals (open squares). The reptilian g0 (upper whisker mark) reveals higher Tb,MGR than the mammalian value (lower whisker mark). Scaling exponents smaller than 0.75 (upper whisker mark) result in higher Tb,MGR and higher exponents (lower whisker mark) in lower Tb,MGR than observed under a ¾ scaling of MGR. Note: MGR scales in non-avian reptiles with about 0.65, in mammals and birds with about 0.75 (Table 1). An exponent of 0.075 in the activation energy term (upper whisker mark) reveals the highest Tb,MGR and an exponent of 0.15 the lowest Tb,MGR (lower whisker mark). Note: Average activation energies of non-avian reptiles (0.757 eV), mammals (0.856 eV) and birds (1.005 eV) are all higher than the 0.65 eV used in the MGR-Tb-equation [67]. A usage of the specific activation energies for these three vertebrate lineages results in lower Tb,MGR values than predicted by the MGR-Tb-equation. The average activation energy of ectothermic fish is 0.433 eV (Downs et al. 2008 [67], upper whiskers).