Dinosaurs fit in an intermediate class between warm and cold blooded animals, a study in the journal Science claims. Scientists compared the growth rates of hundreds of living and extinct species, using growth rings and bone size to calculate the rates for dinosaurs. They linked growth rate to metabolic rate, the measure of energy use that divides warm and cold blooded animals. The study suggests that the dinosaurs fall into a middle category, in a fresh contribution to an enduring debate.
Warm blooded animals, like mammals and birds, need a lot of fuel and use that energy to their advantage, including faster movement and boosted brain power. In burning all that food they also maintain a high, stable body temperature. Cold blooded animals are more economical, but lack those advantages.
“If I were eating sandwiches all day… I might have to eat five,” explained John Grady, the study’s first author and a PhD student at the University of New Mexico. “But a reptile [my size] can eat maybe a couple of sandwiches in a whole week.”
Scientists define these different strategies as “endothermy” (endo for inside; therm for heat) and “ectothermy”. The question of which biological system underpinned the lumbering success of the dinosaurs is arguably “the last big one”, Mr Grady told the BBC – following other big debates over their extinction and their relationship to birds. Edited from Dinosaurs ‘neither warm nor cold blooded’.