Predation
Predation is a major ecological interaction that shapes populations, food webs, and communities. Learn how predator–prey relationships work, why populations can cycle, and how predation influences adaptation and ecosystem structure.
A conceptual model for understanding predation in ecological communities.
In This Article
What Is Predation?
Predation is an ecological interaction in which one organism, the predator, captures and consumes another organism, the prey. Predation is a +/− interaction: the predator benefits by obtaining energy and nutrients, while the prey is harmed.
Predation is broader than the idea of a large animal chasing a smaller animal. It includes many feeding relationships in which one organism kills and consumes another. It is an important force in food webs and can influence population size, behavior, and community structure.
Predation transfers energy from prey to predator while affecting both populations.
A +/− Relationship
Ecologists often describe species interactions using signs. A + means the interaction benefits a species, a − means it harms a species, and a 0 means there is little direct effect.
+
The predator gains energy and nutrients by consuming prey.
−
The prey is captured and consumed, reducing its chance of survival and reproduction.
Predator–Prey Population Cycles
Predation can create feedback between predator and prey populations. When prey become abundant, predators may have more food available, allowing predator numbers to increase. As predator numbers rise, prey may decline. With fewer prey available, predator populations may then decline, which can allow prey numbers to recover.
Real ecosystems are more complicated than this simplified cycle because weather, disease, competition, habitat, food availability, and other factors also affect populations.
Predator and Prey Adaptations
Predation creates natural selection pressures. Predators may have adaptations that improve their ability to locate, capture, or consume prey. Prey may have adaptations that reduce their chance of being detected or captured.
Finding & Capturing
Examples include speed, claws, sharp teeth, camouflage, venom, sensory abilities, and cooperative hunting.
Avoiding & Surviving
Examples include camouflage, warning coloration, mimicry, armor, defensive chemicals, speed, and alarm behaviors.
Predation in Food Webs
Predation is one reason food webs contain many connected feeding relationships. A predator may consume several prey species, and a prey species may be consumed by several predators.
Because species are connected, changing one population can have effects at other trophic levels. Removing a predator, adding a new predator, or causing a prey population to decline can alter the abundance of other organisms in the community. These indirect effects can contribute to trophic cascades.
A predator–prey interaction is part of a network. Food webs help ecologists predict how changes can spread through a community.
Common Misconceptions
If You See This on a Test, Think This
Quick Practice
1. What are the signs associated with predation?
2. Why can predator and prey populations cycle?
3. Give one predator adaptation and one prey adaptation.
4. Why is predation important in a food web?
5. Why is the simple predator–prey cycle only a model?
Key Takeaways
- Predation occurs when one organism captures and consumes another.
- Predation is a +/− interaction: the predator benefits and the prey is harmed.
- Predator and prey populations can influence one another over time.
- Predation can create selection pressures that shape predator and prey adaptations.
- Predators are important parts of food webs and can influence communities through trophic cascades.
- Real predator–prey systems are influenced by many additional environmental factors.
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