Energy expenditures are important to prey species as

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Energy expenditures are important to prey species as well.The zebra that runs every time it sees a lion wastes much time and energy. Lions are not always hunting.When first detected, prey often freeze, stare, spend time studying the carnivore’s intent. Usually it is the carnivore that initiates the chase; the prey responds. Being inconspicuous is obviously important to both predator and prey. Lions are the color of the dead grass they must often skulk through when approaching prey. But it is prey species that often master the art of hiding or resembling something they are not. By doing so, they avoid notice. The spotted fawn, lying stock still at the wood’s edge, looks like a pile of dead leaves, and emits no odor.A herd of running zebras is a blur of black and white stripes, making it difficult to focus on a particular individual. Drab- colored female songbirds resemble pieces of dead bark as they sit on nests. Opossums in a dangerous situation play dead. Many of their potential predators eat only fresh- killed prey and will thus move on from an animal playing ’possum. Mimicry , looking like something in the environment that predators would avoid, reaches its highest expression among insects (Figure 15-23). Some insects not only look like twigs, but gently wave back and forth (even when there is no wind). Some caterpil- lars have large spots on their tail ends that look like huge eyes. Some insects look like lichens, dead leaves, or bird feces. Figure 15-23 Many insects resemble something they are not.These leaf hoppers (a) resemble thorns.This caterpillar (b) mimics bird droppings, while this one (c) looks like a twig. (a) (c) (b)
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516 C HAPTER 15 Population Ecology: How Do Organisms Interact to Form Populations? Some potential prey possess weapons so dangerous or distasteful that predators avoid them at all cost. Porcupines have spines that can cause predators real pain. Skunks emit a spray that not only smells bad, but tastes worse and irritates the eyes. Monarch butterflies, discussed earlier in the chapter, are toxic to predators. So are several species of frogs in Central and South America. Notice that many of these potentially dangerous species are brightly colored. Many advertise their presence and can thus be more easily avoided by predators.Among bees and wasps, black and yellow are common colors.Any predator that knows to avoid the sting of one avoids all.This is an example of Müllerian mimicry , discussed in Chapter 14. This leads us to another form of mimicry. Any insect that happens to be black and yellow will be avoided whether it has a stinger or not.This includes several black and yel- low flies that look like bumblebees.There are several mimics of monarch butterflies, in- cluding viceroys and queens. Most are edible. All are avoided. The edible flies and butterflies are examples of Batesian mimicry , also discussed in Chapter 14.
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