Course: BIS 105 Environmental Biology

Unit 6 Learning Module

Adaptations to Predation

Adaptations to Predation

Prey also have adaptations for avoiding predators. Prey sometimes avoid detection by using camouflage. Cryptic coloration, also known as camouflage, means that species have an appearance (color, shape, or pattern) that helps them blend into the background.

The preying mantis in the left photo looks just like the dead leaves in the background. Can you see the crab in the photo on the right?

Mimicry is a related adaptation in which a species uses appearance to copy or mimic another species. For example, a non-poisonous dart frog may evolve to look like a poisonous dart frog. Why do you think this is an adaptation for the non-poisonous dart frog? Many moths have markings on their wings that look like the eyes of an owl. When a predator comes near, the moth suddenly displays the markings. This startles the predator and gives the moth time to fly away. Mimicry can be used by both predators and prey.

The Viceroy butterfly (right) mimics the unpleasant Monarch butterfly (left).

Some prey species have adaptations that are the opposite of camouflage, called warning coloration. They have bright colors or other highly noticeable traits that serve as an indication to their predators to stay away. For example, some of the most colorful butterflies are poisonous to birds, so birds have learned to avoid eating them. By being so colorful, the butterflies are more likely to be noticed—and avoided—by their predators.

Predation, Natural Selection, and Co-evolution

Adaptations to predation come about through natural selection. When a prey organism avoids a predator, it has higher fitness than members of the same species that were killed by the predator. The organism survives longer and may produce more offspring. As a result, traits that helped the prey organism avoid the predator gradually become more common in the prey population.

Evolution of traits in the prey species leads to evolution of corresponding traits in the predator species. This is called co-evolution. In co-evolution, each species is an important factor in the natural selection of the other species. Predator-prey co-evolution is illustrated by rough-skinned newts and common garter snakes, both shown below. Through natural selection, newts evolved the ability to produce a strong toxin. In response, garter snakes evolved the ability to resist the toxin, so they could still safely prey upon newts. Then, newts evolved the ability to produce higher levels of toxin. This was followed by garter snakes evolving resistance to the higher levels. In short, the predator-prey relationship led to an evolutionary “arms race,” resulting in extremely high levels of toxin in newts.

The rough-skinned newt on the left is highly toxic to other organisms. Common garter snakes, like the one on the right, have evolved resistance to the toxin.