Viewing distance affects how the presence of inedible models influence the benefit of masquerade

Masquerading prey closely resemble inedible objects found in the same locality. These animals gain protection from their predators by causing their predators to misclassify them as the inedible 'models' that they appear to resemble. We recently demonstrated that predators are more likely to misclassify masquerading prey as their models when masqueraders are viewed in isolation from their models than when they are viewed simultaneously with examples of their models. Using domestic chicks (Gallus gallus domesticus) as predators and the twig-mimicking caterpillars of the Early Thorn Moth (Selenia dentaria) as prey, we tested whether this effect was influenced by the relative orientations of models and masqueraders; and the distance from which models and masqueraders could be viewed simultaneously. We found no effect of orientation, but that the cost to masqueraders of being viewed simultaneously with an example of the model declined as the distance between the model and masquerader increased. These results are interpreted in terms of animal cognition, and their implications for the evolutionary ecology of masquerade.