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 naïve 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.

Role of body size and shape in animal camouflage

“…In element imitation, animals resemble specific and common elements of the environment, such as dried leaves or tree branches, and the masquerading species must be situated in the same background as the object being imitated. Conversely, animals resemble uncommon environmental elements in object imitation, such as bird droppings (Mark et al., 2021 ; Skelhorn, Rowland, & Ruxton, 2010 ).…”

“…This provided flea beetles with more time to jump or roll away from the leaf surface. Notably, the animal must match the background environment of the imitated object to benefit from element imitation (Mark et al., 2021 ). If the masquerading animal does not match the size of the imitated object, then predators or prey can easily identify the masquerader based on perception and experience.…”

“…In element imitation, the body size and shape consistency between an individual and the imitated object are paramount to optimal effectiveness. Body size and shape uniformity contribute significantly to achieving a more efficient masquerade effect in specific backgrounds (Mark et al., 2021 ). Notably, discrepancies in body size are tolerable; however, body shape should be closely matched in object imitation.…”

Outstanding issues in the study of antipredator defenses

“…Since in background matching the prey is simply ignored instead of misidentified, there should be no difference in the attack speed regardless of previous experience. But for a predator that has been previously exposed to the inedible model of the masquerader or mimic, it will take longer and be more cautious when attacking the prey compared to a naïve predator (Mark et al., 2021 ; Skelhorn, Rowland, Speed, & Ruxton, 2010 ).…”

From crypsis to masquerade: Ontogeny changes the colour defences of a crab spider hiding as bird droppings

“…At the onset of a trial, a pair of 'buddy' chicks were transferred to the 'buddy arena' (length × width × height: 25 × 50 × 50 cm), which was partitioned off using wire mess from the experimental arena (length × width × height: 80 × 50 × 50 cm). These buddy chicks were visible to the test chicks in the experimental arena (Figure 4b) and were in close proximity to the test chicks during all our experimental trials, thus reducing any potential stress experienced by the test chicks when placed alone in the arena (Mark et al, 2021;Skelhorn, Rowland, Speed & Ruxton, 2010a). We randomly selected a model spider from one of the four types and placed on the centre of a leaf (Alocasia macrorrhiza) in the experimental arena (Figure 4b).…”