This keeps solar radiation out but body heat in. When air temperatures are high, excessive body heat is lost by the animal standing in the shade, pumping heated blood through the highly vascularised bone within the horns. The horns thereby become radiators. Other species sometimes tolerate higher levels of core body temperature. We shall revisit these adaptations in a later column.
Digestion is the one remaining factor included in the list given earlier.
Clearly, there is a connection between respiration and digestion. The energy to actually do the mechanical part of digestion comes from respiration. Digestion both mechanically and chemically processes food, once again in a warm, wet environment so that the essential nutrients are freed for respiration. Different species have differing food requirements and are obviously equipped in order to optimise the types to which they have adapted. Even in human populations there is a wide divergence in food preferences.