Camouflage in heterogeneous environments: an experimental test of the effect of prey colour and pattern complexity (#573)
Background-matching
is one of the most common strategies for visual camouflage. Its efficacy can be
attributed to predator selection for the most conspicuous prey individuals,
resulting in the population’s colour patterns resembling the backgrounds within
their environment. However, in heterogeneous environments, backgrounds can vary
considerably particularly in colour and complexity. This in turn could
influence the selection for varied colour and patterns in a prey population to
match the different background types. In order to determine if the colour
brightness (luminance) and pattern complexity observed in a prey population was
selected for background-matching, we conducted a field experiment to compare
the frequency of predator attacks on colour pattern variants of replica shore
skinks (Oligosoma smithi) in two
habitat types at a sand dune system (light sand versus dark vegetation). We created
four types of clay models (plain light, plain dark, simple dark, complex dark)
and painted them according to reflectance and patterns observed in the
population. We expected models that were dissimilar to their backgrounds (e.g.,
plain light models in vegetation) to be attacked more frequently than ones that
matched their background. A total of 240 models were placed in a grid transect
on sand (<20% vegetation cover) and vegetated (>80% vegetation) areas in the
dunes. Our results show that in the vegetated area, patterned models were
attacked more frequently than plain light or plain dark models. There were very
few attacks observed in the sand area and thus, no difference between the model
types. These results are contrary to our background-matching hypothesis. This may
reflect predators’ preference for the most common or abundant colour pattern
variant in the population (i.e., patterned individuals) and suggests that
predation risk may be influenced more by predators’ search image rather than
conspicuousness per se.