We review how animals conceal themselves in the face of the need to move, and how this is modulated by the dynamic components and rapidly varying illumination of natural backgrounds. We do so in a framework of minimising the viewer's signal-tonoise ratio. Motion can match that of the observer such that there is no relative motion cue, or mimic that of background objects (e.g. swaying leaves). For group-living animals, matched motion and coloration is a special case of the latter 'motion masquerade', where each animal is a potential signal against the noise of other individuals. Recent research shows that dynamic illumination, such as underwater caustics or dappled forest shade, greatly impedes detection of moving targets, so may change the balance of predator-prey interactions.

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Natural habitats contain dynamic elements, such as varying local illumination. Can such features mitigate the salience of organism movement? Dynamic illumination is particularly prevalent in coral reefs, where patterns known as ‘water caustics’ play chaotically in the shallows. In behavioural experiments with a wild-caught reef fish, the Picasso triggerfish ( Rhinecanthus aculeatus ), we demonstrate that the presence of dynamic water caustics negatively affects the detection of moving prey items, as measured by attack latency, relative to static water caustic controls. Manipulating two further features of water caustics (sharpness and scale) implies that the masking effect should be most effective in shallow water: scenes with fine scale and sharp water caustics induce the longest attack latencies. Due to the direct impact upon foraging efficiency, we expect the presence of dynamic water caustics to influence decisions about habitat choice and foraging by wild prey and predators.

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