| dc.description.abstract | Many animals exhibit contrasting shapes across their surface which are thought to help conceal them from potential predators. It has been suggested that these patterns, known as disruptive markings, function by creating false edges that break up the characteristic form of the animal. Some disruptive patterns are graded in tone so that light patches become lighter and dark patches become darker at the points where they converge. Whilst this type of edge enhancement has been shown to improve camouflage efficacy, it still remains unclear how these patterns are typically expressed within real animals and how they may function within a natural setting. In chapter 1, the strength of edge enhancement was quantified for a variety of British moth species through the use of calibrated digital photography. Across the different species, the level of edge enhancement was shown to be more pronounced near the outline of the moth compared to the centre of the wing, caused by a greater offset in the dark edge. In chapter 2, the effect of edge enhancement on camouflage was tested within a natural setting against both avian and human observers. Whilst edge enhancement had no effect on the survival of targets against avian predators, it did affect detection by humans. However, this effect was dependent upon the arrangement of pattern features, with edge enhancement reducing detection when intersecting the outline of the target but increasing detection when expressed only on internal-based markings. Regardless of pattern placement, edge enhanced targets were detected from greater distances. When combined, the results from Chapter 1 and 2 suggest the efficacy of enhanced edges is greatly influenced by their arrangement within a pattern and that they provide camouflage through some function of edge disruption. | en_GB |
