Animals as thermal 'detectors'

Thermal imaging cameras being as expensive as they are, it's interesting to see how observation of animal behaviour can provide clues to some aspects of temperature distribution in the environment. The classic is how to detect that a car has only recently arrived at a property ... if you can't touch the bonnet (hood). A thermal camera will show a warm spot on the bonnet, or (in classic detective mode) you might see that a cat has decided to lie there. Pigeons can also be useful detectors. You will often see birds roosting on top of one building in a group and this is often simply because that roof is warmer; either because of a local heat source such as an air outlet or because that roof is less insulated than the others. Snow will fulfil the same function.

A similar, but inverse, phenomenon has been observed by researchers in Australia. They were using thermal imaging to study how koalas regulate their body temperature, given the hot climate. Hugging trees was one mechanism, the tree trunk being cooler than the surroundings. The animals were observed moving from the top leaves where they feed in winter down to cooler parts of the tree in summer. Conveniently this would provide a perch where the koala could either lie spread on top of a shady branch (as some big cats are seen to do) or wedge themselves in a junction between a large branch and the trunk. Thermal imaging revealed how the koala uses the tree trunk and/or branch as a heat sink.

The study is published (freely accessible) in the Royal Society journal Biology Letters [Biol. Lett. June 2014 vol. 10 no. 6 20140235] and you can read (and see) more on the BBC web site which also outlines other research into how animals can exploit microclimates in trees and other means to combat high temperatures.

Similar themes can be explored from an earlier blog post on toucans and trees.