What drives variety in animal camouflage colouration?

• Main Author: Allen, William Laurence
• Published: British Library 2012
• Subjects: 591.472
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.566692

The diversity of colours and patterns animals' display on their integuments is remarkable and of considerable interest to biologists interested in understanding adaptation. The studies in this thesis have the primary aim of understanding diversity in camouflage pattern appearance by assessing the evidence for correlated evolution between patterns and eco-behavioural variables in a series of comparative studies. Patterns of associations enable competing hypotheses for the adaptive value of patterns to be evaluated Previously, comparative studies have generally measured patterning by classifying patterns into broad subjectively defined categories. This is improved upon by classifying patterns into multidimensional 'camouflage spaces' on the basis of either developmental models of pattern formation, or using image processing techniques on photographs of museum specimens. This enables accurate measurement of intricate aspects of patterning, allowing a more detailed understanding of patterning's adaptiveness. The first empirical chapter examines patterning on the flanks of 37 species of felid and finds that measures related to the lighting environment are the most important predictors of diversity in patterning. In contrast, an analysis of the dorsal patterns of 171 species of snake suggests that antipredator strategy is the main determinant of pattern appearance. Longitudinal stripes and plain patterns were associated with traits which suggest they are effective camouflage during flight from threat, whereas blotched and banded patterns were associated with snakes that can fight off threats, defending themselves with potent venoms. The final study shows how only the self-shadow concealment hypothesis explains variation in the appearance of countershading profiles of 114 species of ruminant, and that countershading appearance is frequently within the range of effective self-shadow concealment predicted by a model of optimal countershading. Together these studies show how the drivers of diversity in patterning are numerous and varied, and while some species present exceptions, overall trends reveal exquisite associations between pattern appearance and eco-behavioural traits. These associations enabled existing hypotheses to be evaluated and new proposals to be suggested for how camouflage patterning adapts and diversifies to promote survival given the environment of an organism and its behaviour within it.