Avoiding detection through camouflage is often key to survival. However, an animal’s appearance is not the only factor affecting conspicuousness: background complexity also alters detectability. This has been experimentally demonstrated for both artificially patterned backgrounds in the lab and natural backgrounds in the wild, but only for targets that already match the background well. Therefore, we do not know whether habitats of high visual complexity provide concealment to even relatively poorly-camouflaged animals. By measuring predation rates of artificial prey which differed in their degrees of background matching to tree bark, whilst also measuring the natural background complexity, I was able to explore this issue. Higher background orientation clutter (edges with varying orientation) reduced the detectability of all but the poorest background matching camouflaged treatments; higher background luminance clutter (varying achromatic lightness) reduced average mortality for all treatments. Another gap in our knowledge is the precise mechanism in which visual complexity affects target detectability. By using artificial grey-scale targets and backgrounds, I was able to isolate and manipulate the normally covarying factors which comprise ‘complexity’ in natural habitats. By doing this, I showed that reduced detection by humans is not explained by greater information content (entropy) or higher variance in the background’s features (feature congestion) per se, but instead by reduced signal-to-noise ratio in the perceptual dimension that potentially distinguishes target from background. This combination of field and laboratory experiments suggests that, although highly salient targets will always be easily detected, even relatively poor camouflage (in terms of background matching) can be mitigated by a more complex background. This has implications for both camouflage evolution and habitat preferences, and opens questions into when the term complexity should be used, and how viewers learn the characteristics of the background.
How background complexity impairs target detection and can mitigate poor camouflage.
Rowe, Z. W. (Author). 2 Dec 2021
Student thesis: Master's Thesis › Master of Science by Research (MScR)