Data from: Camouflage using surface disruption: the importance of corners versus edges

Disruptive colouration is a common mode of camouflage used by predators
and prey to conceal their body contours. Several studies have noted the
importance of edge disruption in breaking up two-dimensional (2D) body
outlines, but less is known about how disruptive colouration hinders the
detection and recognition of three-dimensional (3D) body shapes.
Specifically, in the context of animal camouflage, it is not clear how the
location of three-dimensional (3D) surface disruption affects prey
detection. In human visual systems, it is known that corners, not edges,
of an object are critical for shape processing and contour completion.
However, whether corners are also critical for 3D shape recognition in
non-human animals has not been investigated. To test this, in Experiment
1, we presented 3D-printed moth-like targets with either corner
disruption, edge disruption, or no disruption to wild, free-living birds.
We repeated this in Experiment 2 with 2D targets, comprising images
matched to Experiment 1, to determine if pictorial cues (patterns that
produce an impression of depth) had the same effect. Contrary to our
predictions, we found no effect of surface disruption location on survival
probability for either 3D or 2D moth targets. Contrary to previous work,
we found that targets with disrupted surfaces, irrespective of the
disruption location, did not have higher survival than those with
continuous surfaces. However, when the data from both experiments were
combined, we found that 3D targets had higher survival than 2D targets.
Although the disruptive and non-disruptive targets differed in contrast,
this did not account for the variation in survival. Indeed, most of the
variation in our data was explained by the spatial and temporal structure
of the data, owing to different predator communities and seasonal
variation in predation risk. Given that corners are critical for shape
recognition in humans, developing an appropriate system to test visual
perception in non-human animals will provide key insights into the role of
visual perception in the predator-prey arms race.