Core temperature in various species

The range of body core temperature is, in most mammals, closely regulated. This is also true of birds. In many ectotherms, species which were once classified as poikilotherms, a relatively stable body core temperature is achieved during the daytime by shuttling between warmer and cooler regions, i.e., by a behavioural means. The regulated core temperatures vary with the species, and some of these ranges are shown in Table 2.1. In this Chapter I propose to give a sufficient outline of current thinking on the mechanisms of normal thermoregulation to enable the non-specialist reader to follow the later chapters on the disordered thermoregulation of body temperature which occurs in fever. It is not intended to give a full account of the details of all parts of the thermoregulatory neural mechanisms, or to detail the arguments for and against such things as the concept of ‘set point’. These matters would require a book in themselves, and the reader is referred to such texts as Bligh (1973), Boulant et al. (1989), Schönbaum & Lomax (1990), and Gisolfi et al. (1993).

Sites of temperature measurement

There are several sites at which body temperatures are measured, especially in mammals. There is probably not a single temperature site which gives a measurement common to all of the body core. The rectal temperature is warmer than the oesophageal and mouth temperatures by about 1 °C.