Differential expression of seasonal energetic adaptations generates a continuum in the trophic status of endotherms during winter.
They are endotherms and they can finely tune the thermal, water, and chemical balance of their bodies from minute to minute.
Extant birds are accomplished endotherms and many maintain the highest body temperatures.
For example, display and assessment of potential mates may be less costly for endotherms at higher temperatures than at lower temperatures.
‘How did endothermy evolve in mammals?
The main basis for the faster absorption of nutrients in mammals to fuel endothermy and increased activity relative to reptiles has been shown to be a much greater intestinal surface area in mammals.
However, the problem is severe for an endotherm, particularly a small endotherm, which must maintain a steady internal temperature and has a considerably greater demand for respiratory oxygen.
Different lines of evidence indicate that endothermy as it is known from modern birds and mammals may not have been feasible for most, particularly larger, dinosaurs.
