As a solution, disruptive coloration involves relatively high contrast markings near the edge of the body to break up the outline 3, 17, 18. The efficacy of background matching can be limited by the outline of an animal’s body, creating discontinuities with the background that make it more conspicuous to predators 17. At least one study 1 has also provided direct quantification of site-specific background matching in an intertidal crustacean, the sand flea ( Hippa testudinaria), demonstrating that individuals match the colour and luminance of their own beaches more closely than of neighbouring beaches. 14, 15) to studies demonstrating its utility in preventing detection of potential prey in both the lab (e.g. While not always directly quantified in animals, background matching is likely to be widespread across many habitats and species, ranging from classic examples of concealment (e.g. Background matching reduces the deviation in features between the appearance of an animal and its surroundings, and is therefore specific to the visual background where it has arisen 12. Phenotype-environment associations have to date largely been considered in the context of background matching 11, 12, a widespread form of camouflage involving resembling the general colour and pattern of the environment (e.g. Indeed, a great deal of work in artificial systems has explored how camouflage can be optimised under specific contexts (see below). This poses the question of how camouflage should be tuned to work best in different visual environments and contexts. Nonetheless, camouflage, and its effectiveness, is widely appreciated to involve an interaction between the appearance of the organism and that of its background. These examples of phenotype-environment associations are highly suggestive of a camouflage function, but past work has rarely demonstrated or quantified the actual camouflage resulting from any match to the local environment that is, phenotype-environment matching (but see 1). Indeed, selection has driven correlations in appearance between individual phenotypes and backgrounds in a wide range of animals, from rodents and lizards in terrestrial habitats 6, 7 to crabs in marine habitats 2, 8, 9, and even in plants 10. It has long been appreciated that these associations are a product of natural selection 3, 4, with individuals camouflaged against the prevailing visual environment 5. Many animals exhibit visual similarities with their environment, commonly referred to as ‘phenotype-environment associations’ 1, 2. Our study demonstrates facultative expression of camouflage strategies dependent on the visual environment, with implications for the evolution and interrelatedness of defensive strategies. As expected, rock pool individuals had significantly higher edge disruption than mudflat crabs, whereas mudflat crabs more closely matched the substrate than rock pool crabs for colour, luminance, and pattern. Using predator (bird and fish) vision modelling and image analysis, we quantified background matching and disruption in crabs from rock pools and mudflats, predicting that disruption would dominate in visually complex rock pools but background matching in more uniform mudflats. Here, we test the camouflage strategies of the shore crab ( Carcinus maenas) in two habitats, being a species that is highly variable, capable of plastic changes in appearance, and lives in multiple environments. These ideas have rarely been tested and previous work focuses on artificial systems. In contrast, disruptive coloration, which disguises body outlines, may be effective against complex backgrounds.
Camo background Patch#
This approach, however, may be ineffective in complex habitats where matching one patch may lead to increased visibility in other patches. A common strategy is background matching, resembling the colour and pattern of the environment. Camouflage is a key defence across taxa and frequently critical to survival.
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