Edinburgh Napier University

  Infrared thermography (IRT) is a technique that determines surface temperature based on physical laws of
radiative transfer. Thermal imaging cameras have been used since the 1960s to determine the surface
temperature patterns of a wide range of birds and mammals and how species regulate their surface
temperature in response to different environmental conditions. As a large proportion of metabolic energy is
transferred from the body to the environment as heat, biophysical models have been formulated to determine
metabolic heat loss. These models are based on heat transfer equations for radiation, convection, conduction
and evaporation and therefore surface temperature recorded by IRT can be used to calculate heat loss from
different body regions. This approach has successfully demonstrated that in birds and mammals heat loss is
regulated from poorly insulated regions of the body which are seen to be thermal windows for the dissipation
of body heat. Rather than absolute measurement of metabolic heat loss, IRT and biophysical models have been
most useful in estimating the relative heat loss from different body regions. Further calibration studies will
improve the accuracy of models but the strength of this approach is that it is a non-invasive method of
measuring the relative energy cost of an animal in response to different environments, behaviours and
physiological states. It is likely that the increasing availability and portability of thermal imaging systems will
lead to many new insights into the thermal physiology of endotherms.