Aside from big size, how did theropods keep cool and satis$r their thirst when things were hot? walking dinosaur costume Smaller species could have used their air-sac systems and rapid panting as internal evaporative cooling ventilators. Living birds do this. When small animals pant, they breathe at the resonant frequency of their rib cage to minimize the energy used. The resonant frequenry of big-animal chests is too low for rapid panting, so they cannot use internal cooling. But with their bulk, they did not need it as badly. The few species with finbacks could have used them for cooling, as long as the temperatures were not too high. Regardless of their size, the body fluids of the predatory dinosaurs’ victims would satisSr much of their water needs, and as predators they could always drive other dinosaurs away from water holes and get the most of what was available.
Robert Bakker has recently come up with another way to measure extinct animal metabolic rates-fossil trackways,2s of which there are many thousands made by a wide variety of species. It is fairly simple to estimate the speed at which a trackway was made (Animatronic dinosaur). It turns out that early amphibians and primitive reptiles “cruised” at a slow but constant speed. All but a few trackways show them walking only a couple of miles per hour. This is quite different from fossil mammal herbivores, which typically cruised much faster. Faster yet were mammalian carnivores, which paced along at 3 to 6 mph. Animatronic dinosaur costume What is happening here is fairly straightforward. Because the mammals have to consume more food to keep up with their voracious metabolisms, they have to cover more territory to find it. So they move faster. It is all part of the race to expend more energy in order to get even more energy. As you mrght expect, dinosaur trackways show that they cruised fast-some 2 to 4 mph for the herbivores, even faster for the predators. This can only mean that they had a hunger of endothermic proportions. As always, this applies to theropods of all sizes, so bulk endothermy could only explain part of the phenomenon.