Camouflage efficiency in a colour-polymorphic predator is dependent on
environmental variation and snow presence in the wild
Abstract
Colour polymorphism can be maintained by colour morph-specific benefits
across environmental conditions. Currently, the amount and duration of
snow cover during winter decreases especially in northern latitudes,
which can alter the potential for camouflage of animals with light and
dark morphs. Tawny owls, Strix aluco, are colour polymorphic avian
predators with dark (brown) and light (grey) colour morphs, where the
grey morph is presumed to enjoy camouflage benefits under snowy
conditions. We studied the two tawny owls’ morphs’ camouflage potential
using passerines’ probability to detect and mob in the wild during
spring, autumn, and winter with and without snow. We find that grey
tawny owls are both less likely to be detected and have a lower
probability of being mobbed compared to brown tawny owls only during
snowy winters. The two colour morphs therefore experience differential
benefits across snow conditions, which may help to maintain colour
morphs in the population, although further warming of winter climate
will reduce the potential for camouflage for grey tawny owls in northern
latitudes.