Bat, thermogram footage. Thermography records the temperature of surfaces by detecting long-wavelength infrared radiation. The colours show variations in temperature. The scale runs from white (warmest), through yellow, orange, red and purple to blue (coldest). A colour-coded temperature scale is at right, ranging from 18 degrees Celsius (dark blue) to 38 degrees Celsius (white). The bat is roosting here, hanging upside down by its feet with its wings wrapped around its body. This footage shows that the most heat (bright yellow areas) is being radiated from the bat's head. Fur insulates the rest of the body.