Camouflage can be attained via mechanisms such as background matching (resembling the general background) and disruptive coloration (hindering the detection of an animal’s outline). However, despite much conceptual work with artificial stimuli there have to date been few studies of how such camouflage types work in real animals in their natural environments. Here, using avian vision models and image analysis, we tested which concealing mechanisms operate to provide camouflage during behavioral choice of a resting position in two bark-resting moths, Hypomecis roboraria and Jankowskia fuscaria. We found that both species reinforced their crypticity in terms of both background matching and disruptive coloration. However the detailed mechanisms (such as achromatic/chromatic matching or pattern direction matching) that each species exploits differed between the two species. Additionally, we found substantial correlation between the degree of background matching and disruptive coloration, which supports previous work suggesting that these two different concealing mechanisms work together to confer camouflage. Our results clearly demonstrate that an appropriate behavioral choice of background is essential to improve camouflaged against natural predators, and highlight the interrelation between different concealing mechanisms in real prey.

Geometrid moths are well known for their camouflage. Their wing color patterns resemble tree bark which is their preferential resting place. After landing on tree bark, many of them show the re-positioning behavior which makes the moths more cryptic effectively. Previous study revealed that moths perceive structural cues from tree bark to position their bodies. However, to date, it is not clear which sensory organ is used during re-positioning behavior. We performed a series of experiments to find out how (i.e. by using which sensory organs) moths seek out an appropriate position and body orientation. We used a geometrid moth, Jankowskia fuscaria, to test our hypothesis. We hypothesized that one of four sensory organs (eyes, antennae, front legs, and wings) may be responsible for their ability to find more cryptic position and body orientation. We amputated one of these organs and observed whether they are still able to find a cryptic position. The results indicates that visual cue is essential for their cryptic-positioning searching behavior, but antennae or front legs are not. Tactile cues from their wings seem to have a role in their behavior, but the evidence is flimsy. Therefore we cautiously conclude that moths mainly rely on visual cues (most likely through eyes) to orient their bodies on resting place, but additional tactile cues from their wings seem to play an additional role.

The diverse color pattern of insects are products of natural/sexual selection and affect their survival and reproductive success. Therefore understanding the function of the color patterns is critical to understand their life-history traits such as defensive/territorial behavior or mating strategies. However how we (humans) see and perceive their colors does not reflect the true nature of the insect colors because the insect colors have evolved to work best for the appropriate receiver. For example, defensive coloration have evolved to deceive predators’ eyes, and sexual traits of males have evolved to attract the eyes of the conspecific females. The visual system (therefore the perception of color, too) substantially differ between species and it is important to consider the appropriate receiver’s point of view (visual system) to properly understand the functional aspect of insect color pattern. Here I introduce the concepts of visual modelling of animals’ point of view to study insect coloration and present a case study research on camouflage of moths.

Prey species should avoid areas where predation risk is high. However, if this is impossible, prey should reduce activities that may make them conspicuous and attract predators, such as foraging or mating. Thus, predation risk should change behavioral pattern of prey species. Not all species have same anti-predator behavioral patterns because they have evolved in the presence of different types or number of predators in their habitat. In this study we measured microhabitat use and escape initiation distance to identify how sensitive each species is to approaching predators. We measured jumping performance and morphological characteristics to reveal the relationship between jumping and morphology and whether jumping is helpful for escaping from predators' attack. Finally, we compared the survival rate among three species to identify how survival rate is affected by anti-predator behavioral patterns. The survivorship was related to microhabitat use and to the escape initiation distance, rather than on the jumping ability. We predicted that a species with the best survival rate will have superior jumping ability in order to escape from predators at the moment when they were attacked by predators. The jumping ability, however, was probably limited by hydrodynamic and morphological constraints, so jumping appears to contribute little to successfully escaping from predators’ attacks.

Defended (distasteful or toxic) prey are often characterized by conspicuous coloration and this phenomenon is called "aposematism". The main advantage of aposematism is that it promotes faster learning by predators to avoid the prey. Some defended prey species use a different strategy; they remain cryptic in the normal state, but display conspicuous aposematic signal (which is normally hidden) in response to a predator's approach/attack. This anti-predator strategy of a defended prey has not been well studied yet although it can theoretically give the benefits of both camouflage and aposematism. Here, we investigated the effectiveness of this ‘hidden-aposematic signal’ as a warning signal. Using wild tits (Parus minor) as predator and novel artificial prey models (which mimics wings of insects), we tested whether hidden conspicuous signal of a defended prey enhances the avoidance learning rate of predators and how does it compare with the typical conspicuous/non-conspicuous signal. We found that hidden conspicuous signal indeed enhances the avoidance learning rate of predators in comparison with the non-conspicuous signal. However the overall learning rate by predators to avoid the defended prey was slower than for the normal conspicuous signal. Our results suggest that the prey with hidden-aposematic signals could enjoy both the benefits camouflage and the benefits of aposematism that are however lower than benefits from a typical aposematic signal. We, for the first time, highlight the functional aspect of a unique, but yet largely ignored, defensive coloration of prey.

Cryptic color patterns in prey are classical examples of adaptations to avoid predation, but we still know little about behaviors that reinforce the match between animal body and the background. For example, moths avoid predators by matching their color patterns with the background, but the contribution of their behavior to their crypticity have not been well understood. Here, we report the previously underappreciated ability of moths to find the locally most cryptic spot and body orientation by using two species Hypomecis roboraria and Jankowskia fuscaria. We show that body positioning behavior, performed frequently by moths after landing on bark, results in a significant increase of the camouflage effect provided by their cryptic color pattern alone. We also found that moths recognize multiple background cues, such as furrow structure, visual patterns, and roundness to position and orient themselves. Our study demonstrate morphological adaptations, such as color pattern of moths, cannot be fully understood without taking into account a behavioral phenotype that coevolved with the morphology for increasing the adaptive value of the morphological trait.