What would happen if lions, cheetahs, hyenas, and other predators of the African Savannah disappeared? With no predators hunting them, the populations of wildebeests, gazelles, and other herbivores would explode. They would overrun the Savannah and destroy the vegetation. And what if wildebeests and gazelles vanished? With nothing to eat, carnivores would either starve or turn on each other. These scenarios are hypothetical, but they aren't far-fetched. In fact, the relationship between predator and prey is far more complex than these examples suggest.
What is a Predator-Prey Relationship?
Nearly all species in a given ecosystem are interdependent. Lose one species, and others can suffer badly. This dependence can be sorted into two main types: symbiotic relationships and predator-prey relationships.
Predator-prey relationships play a crucial role in keeping an ecosystem balanced. A tilt on either side can trigger a domino effect across the whole environment. If prey numbers drop, predators find it harder to find food, and they struggle to reproduce. If predator numbers fall, herbivores run riot in the ecosystem.
Examples of Predator-Prey Relationships
1. Cheetah and Gazelle
In the African Savannah, the most famous predator-prey pair is the cheetah (the world's fastest land animal) and the gazelle. In the open grasslands, the gazelle has nowhere to hide. Its only option is to outrun the cheetah. The gazelle knows that a cheetah runs fastest in a straight line, so it escapes by sprinting in a zig-zag pattern. It's a classic example of the survival of the fittest.
2. African Wild Dogs and Zebras
The African wild dog and zebra relationship is very different from the cheetah-gazelle chase. Wild dogs are small, but they make up for it with pack behavior and remarkable stamina. The strategy is simple: coordinate an attack, isolate an individual, tire it out, then bring it down by grabbing its tail and nose. Zebras fight back with camouflage, their striped coats make it hard for predators to single out one animal from the herd.
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3. Canadian Lynx and Snowshoe Hare
Canadian biologist Charles Gordon Hewitt studied the number of lynx and hare pelts brought in by hunters. He found that the two species are tightly linked: the population of the Canadian lynx rises and falls with the snowshoe hare population. Further research showed that when hare numbers drop, food becomes scarce, and that directly lowers the reproduction rate of the lynx.
4. African Lion and Warthog
Wildebeests and Cape buffaloes make up most of an African lion's diet, but lions also hunt warthogs whenever they get the chance. Warthogs are not easy prey, though. Their eyes sit high on their head, giving them a wide field of vision, and their sharp tusks can cause serious injuries. A lion that takes too long to make the kill can end up worse off.
5. Wolves and Moose (Isle Royale)
For researchers, the relationship between wolves and moose on Isle Royale is one of the clearest examples of predator-prey dynamics anywhere. On this isolated island, moose are almost the only prey available to wolves. After studying this relationship for decades, researchers found that when wolves eat too many moose, food runs short, and that keeps the wolf population in check too.
6. Great White Shark and Elephant Seal
In the marine biome, the great white shark is the apex predator. It usually preys on elephant seals. For seals, the safest place is dry land. But a seal can't stay ashore forever, it would starve. The moment it enters the water, the great white's exceptional hearing locks onto it. It all comes down to whoever blinks first.
7. Osprey and Fish
In freshwater habitats, a diving osprey is one of the most dramatic predator-prey moments in nature. Ospreys live almost anywhere they can find fish. They spot any movement below the surface with their exceptional eyesight, then strike at lightning speed. Opposable claws and sharp spiny scales on their toes give them a firm grip on slippery fish. The fish's best defense? Stay in deep water.
8. Arctic Fox and Lemmings
In the tundra biome, the Arctic fox and lemming pair shows one of nature's most striking population cycles. Lemming numbers are cyclic, they fluctuate every three to five years. In regions where lemmings are the main prey, the Arctic fox population follows the same up-and-down pattern. When lemmings are plentiful, fox litters are large. When lemmings are scarce, the foxes have far fewer pups.
9. Grizzly Bear and Salmon
In some predator-prey relationships, the prey has almost no defense. The grizzly bear and salmon are a perfect example. Salmon cannot escape a waiting bear in shallow river shallows. A poor salmon run can have a domino effect on the health and population of grizzly bears. Researchers are worried that poor salmon runs will become more common because of overfishing and climate change.
10. Cat and Mouse
At the most basic level, a cat chasing a mouse is one of the simplest examples of a predator-prey relationship, and probably the one you know best. That said, a pet cat may not always hunt a mouse for food, especially if it gets its meals from a bowl. But the instinct is still there.
How Predator and Prey Evolve Together
Both the predator and prey evolve over time. The predator evolves to hunt better; the prey evolves to avoid being hunted. Both use behavioral and physical adaptations to outcompete each other. A predator that is ill-equipped to hunt (because of old age or injury) has a bleak future. The same is true for prey that cannot escape.
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