Indeed, Thayer's (1896, 1909) and Cott's (1940) works are still hugely influential and contain a range of untested ideas. However, in spite of its long history and widespread occurrence, research on natural camouflage has not progressed as rapidly as many other areas of adaptive coloration, especially in the last 60–70 years. There are several reasons for this, including that human perceptions have often been used to subjectively assess a range of protective markings, rather than working from the perspective of the correct receiver. In general, the mechanisms of camouflage have often been erroneously regarded as intuitively obvious. Furthermore, many researchers may have found more showy types of animal coloration, for example, aposematism, mimicry and sexual ornamentation, more exciting than the often (but not always) duller colours and patterns used for camouflage. Thus, until recently, the study of natural camouflage has progressed slowly; little had changed in our understanding of how camouflage works since the landmark book of Hugh Cott in 1940. Therefore, many of the striking examples of camouflage, such as those discussed above, have not been formally tested, and the benefit that these different types of concealment bring to animals has rarely been quantified in survival terms and how they specifically …show more content…
We do not doubt that categorisation of appearances has merits in some circumstances, such as for comparative studies (e.g. Stoner et al. 2003). However, others advocate far more extensive uses of descriptive terms. For example, Hanlon (2007) argues that animal camouflage patterns can effectively be defined by three basic pattern classes, ‘uniform’, ‘mottle’ and ‘disruptive’, and that while initially based on appearances in cephalopods, which can adjust their patterning, the grouping seems to apply to other animals as well. We feel this approach is counterproductive and will lead to confusion, particularly because such an approach does not aid the understanding of how different forms of camouflage function or the different visual mechanisms involved and how these, in turn, impose selection on animal coloration. Instead, definitions should be based on what camouflage does (even if the specific visual processes are uncertain). This is crucial because similar pattern types may have entirely different functions in different animals and circumstances. Stripes, for instance, which Hanlon (2007) groups as disruptive could equally well function in background matching, distraction, as warning signals, or with making estimates of speed and trajectory difficult (motion dazzle), depending on the context. In addition, differences in visual perception across