Wallaby, thermogram. A thermogram shows variation in temperature on the surface of an object, measured by the long-wave infrared radiation it emits. The temperature scale is colour-coded and runs from purple (6 degrees Celsius, coldest) through blue, green and yellow to red (warmest, 23 degrees Celsius). The wallaby's fur insulates it from the cold. The covering of fur is thinner on its feet and hands which is why heat loss is greater from these parts.