Distance-dependent defensive coloration

• Published in: Current biology 2014-12, Vol.24 (24), p.R1157-R1158
• Main Authors: Barnett, James B., Cuthill, Innes C.
• Format: Article
• Language: English
• Subjects: Animals; Color; Female; Food Chain; Humans; Male; Songbirds - physiology; Tenebrio - physiology; Visual Perception
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2014.11.015

Camouflage and warning coloration are usually viewed as alternative defensive strategies at opposite ends of the conspicuousness continuum. However, camouflage is compromised by factors such as habitat heterogeneity and motion [1], and aposematism bears the cost of ineffectiveness against ignorant, hasty or nutritionally stressed predators [2]. To reduce these costs, it has been suggested that camouflage and warning coloration can be combined by the use of patterns that are detectable at different distances [3]. This hypothesis finds support in experiments on humans searching for photographs of animals on computer screens [4–6]. Using spatial frequency blending, a technique developed in computer graphics [7], we show that such distance-dependent defences are effective under field conditions against natural, avian predators. We isolate the mechanism as concealment-at-a-distance and avoidance-close-up. This supports the argument that color patterns need not be optimised for one defensive strategy, and that signals may change with viewing conditions. Barnett and Cuthill show that camouflage and aposematism can be combined in patterns that are highly conspicuous at close range but camouflaged when viewed from a distance. This creates a dual-function defence which is more effective than either strategy in isolation when tested under field conditions with wild avian predators.