Ecology: Organisms and Their Environments
Topics in Depth
The Theme of Predation in Ecology: Organisms and Their Environments
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!_CITATION_UUID_79A597EC4A3949C5A17339911B9A6031_
Predator adaptations to enhance predation can be as fascinating and complex as prey defense adaptations, but we won’t break them into neat categories here. Instead, we will provide a few examples, and leave it to you to explore the Internet and some hard paper things called books for other interesting examples.
One predator adaptation that you may be familiar with is that used by the angler fish. Yup, it's Finding Nemo time again. This clever creature lives in the darkest parts of the ocean and has a luminous tassel that it dangles in front of its mouth. Unwary prey, named Marlin and Dory, of course, swim toward the light and become easy targets for the angler fish. If you think about it, human "anglers" use the same technique in their attempt to catch unwary fish.
Other predator adaptations include developing resistance to chemical toxins, increased perception, and faster running ability. In the end, though, predators rarely become so efficient that their prey don’t stand a chance. What do you think would happen if they did?
Predators rely on prey populations, and therefore, the numbers of prey available will determine the number of predators that are able to survive. This interaction results in a kind of periodic cycle over time because the number of prey track the abundance of predators. Read more here.
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