5 Metabolism and body temperature
5.1 Warm-blooded vs cold-blooded
This section is concerned with another key mammalian characteristic. LoM highlights some of the essential terms and ideas - such as the notion of warm-bloodedness - but for more thorough study, some technical background is needed.
Activity 3
Watch the 'A Winning Design' on the DVD from 00.00-06.25, which emphasises the diversity of mammalian habitats. Using that information, plus your recollection of the LoM chapter, suggest some benefits of 'warm-bloodedness' to mammals and some of the implications of this strategy.
Discussion
Mammals are no longer at the mercy of the environment; by contrast, the body temperature of most amphibians, for example, is closely linked to outside temperatures. Thus the arctic fox remains warm and active in very cold conditions. But being warm-blooded has a high energetic cost. (In mammals, as much as 80-90% of the energy obtained from their food is needed to maintain body temperature.)
LoM p. 12 points out that non-mammals generate body heat, giving examples of a python and some species of fish, such as tuna. A reptile basking in the sun can become as warm to the touch as a mammal. If you've encountered a mammal during hibernation - perhaps a cautious investigation of a hedgehog - you'll probably have found it surprisingly cold to the touch. So in describing what's special about the body temperature of mammals, cold-blooded and warm-blooded are terms best avoided.