Lichen moths do not benefit from ‘element imitation’ masquerade in the absence of a matching background

Abstract

Predation places significant selection pressures on prey species and many have evolved incredible and diverse colour patterns in response. A fascinating example of such adaptive colouration and morphology is masquerade, a camouflage strategy in which organisms resemble innocuous and inedible objects, such as leaves or twigs. Masquerading prey avoid predation by being misclassified as irrelevant parts of the environment, rather than as food. Here we assess a putative case of masquerade in the North Island lichen moth, Declana atronivea (Geometridae), an endemic New Zealand species with intricate black and white forewings that appear to resemble lichen. Lichen masquerade is a type of ‘element imitation’ in which the object being mimicked forms a common element of the environmental pattern. However, unlike discrete objects, such as leaves and twigs, lichen may be difficult to distinguish as a distinct entity. This raises the question of whether D. atronivea can be said to look like ‘a’ lichen, or whether its body colouration appears as a component of a larger patch of lichen. In this case, does the lichen resemblance function as a form of masquerade, or is it an example of background matching? Using laboratory experiments with domestic chicks (Gallus gallus) as predators, we investigated whether D. atronivea moths avoid predation by being misclassified as lichen. We exposed naive and experienced chicks to D. atronivea and compared their responses, predicting that if the moths do benefit from masquerade, chicks with previous experience of lichen would take longer to attack. Our hypothesis was not supported; there was no significant difference in predator interaction regardless of prior experience, suggesting that, in the absence of a matching background, D. atronivea do not benefit from masquerading as lichen. Rather, this may be a case of context-dependent misclassification, or perhaps the forewing colouration promotes concealment through crypsis.