Study Guide

Ecology: Organisms and Their Environments - Predation

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We suspect that if you were to ask your grandma to name a species interaction, she would say "Eh? Come again? What did you say?" But then, she would probably say "Predation." Right? Our grandma would.

We imagine that when most people think about ecology, they think about predators hunting prey. Then again, Shmoop is really imaginative. Still, nature shows love to entice audiences with gory accounts of bloody lion hunts. They do not usually spend a lot of expensive airtime showing hungry little fish competing for plankton. This is probably a wise business decision. But, it is important for you to remember that every species interaction, no matter how boring the TV show depicting it might be, can pose a powerful force in determining the structure of a community. With that said, we should still take a closer look at predation, aka the species interaction where one species eats another. We can see you licking your chops.

In most cases, predators and their prey are involved in an extremely complex and age-old interaction. Predation rarely results in the extinction of the prey population. Instead, predation often results in what biologists call an "evolutionary arms race," where prey adapt physically, behaviorally, and chemically to defend against predator attacks, and predators likewise adapt to circumvent new prey defenses and enhance predation. The circle of life.

First of all, let’s look at some of the snazzy ways that prey species have adapted to defend against predation.

In general, prey defense adaptations can be broken into three main categories:

  • Physical defenses
  • Chemical defenses
  • Behavioral defenses

The fishing spider provides a good example of a species using a physical defense against predation. This clever arachnid will actually shed some of its legs to allow it to escape. Other physical defense adaptations include the quills of porcupines, the spines of cacti, and the bright "warning" coloration of some butterflies and moths. Even the seasonal reproductive periods, or breeding seasons, used by many different species can provide a physical defense against predation because the sheer number of offspring make it unlikely that predators can have a large impact on any given individual’s reproductive success. In other words, prey don't let predators cramp their styles.

The skunk provides a familiar example of a species that uses a chemical defense. In fact, many animals use noxious chemicals to ward off potential predators, including bombardier beetles, possums, and even plants like poison ivy and foxgloves. Foxgloves, by the way, can cause vomiting, hallucinations, convulsions, and even death if you eat one. We suggest...not. One of the most disgusting chemical defenses is used by the horned lizard, which will squirt blood from its eyes when threatened. In short, don’t mess with these guys.

The last prey defense category includes behavioral strategies used by organisms to avoid detection, attack, capture, or consumption by a predator. Common behavioral defenses include sleep patterns, such as only being awake during the night, flight (for obvious reasons), and playing dead. Tarantulas use a less well-known behavioral defense. These enormous spiders will pull out their painfully barbed back hairs and literally throw them at predators. As if tarantulas weren’t scary enough!blank" href="">here.

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