Crypsis

Abstract: The study of camouflage has a long history in biology, and the numerous ways of concealment and disguise found in the animal kingdom provided Darwin and Wallace with important examples for illustrating and defending their ideas of natural selection and adaptation. Thus, various forms of camouflage

Abstract: A model, developed previously by several authors, predicting the diet which maximizes a predator's rate of energy intake is generalized to include prey recognition times, the probability of prey misidentification, and learning by the predator. The model predicts that the most valuable prey are always eaten when encountered, but if their encounter rates are too low the diet expands to include less valuable prey. Less valuable prey may be eaten when their relative abundances are high even when the preferred prey are plentiful if there is a finite recognition time or, alternatively, if there is a significant probability of the predator mistaking them for the preferred prey. Crypsis may cause a predator to mistake a proportion of inedible objects for the real prey, thereby decreasing the expected value of the cryptic prey. When the cryptic prey becomes scarce the predator may specialize on intrinsically less valuable noncryptic prey. By learning to handle prey more efficiently, the predator may effectively tr...

Abstract: Frequency-dependent predation may maintain or prevent colour pattern polymorphisms in prey, and can be caused by a variety of biological phenomena, including perceptual processes (search images), optimal foraging and learning. Most species are preyed upon by more than one predator species, which are likely to differ in foraging styles, perceptual and learning abilities. Depending upon the interaction between predator vision, background and colour pattern parameters, certain morphs may be actively maintained in some conditions and not in others, even with the same predators. More than one kind of predator will also affect stability, and only slight changes in conditions can cause a transition between polymorphism and monomorphism. Frequency-dependent selection is not a panacea for the explanation of variation in animal colour patterns, although it may be important in some systems.

Abstract: Conspicuous warning signals of unprofitable prey are a defense against visually hunting predators They work because predators learn to associate unprofitability with bright coloration and because strong signals are detectable and memorable However, many species that can be considered defended are not very conspicuous; they have weak warning signals This phenomenon has previously been ignored in models and experiments In addition, there is significant within- and among-species variation among predators in their search behavior, in their visual, cognitive, and learning abilities, and in their resistance to defenses In this article we explore the effects of variable predators on models that combine positive frequency-dependent, frequency-independent, and negative frequency-dependent predation and show that weak signaling of aposematic species can evolve if predators vary in their tendency to attack defended prey