5 Apex Predators-Mid

Apex Predators FOCUS Question How do top predators shape ecosystems?

Life at the Top A polar bear silently slips into the Arctic Sea. On a nearby iceberg, a seal snoozes in the sun. It has no idea that a massive hunter is sneaking up behind it... Half a world away, a herd of wildebeest approach a river cautiously, sniffing the air. They know that crocodiles lurk in these waters, but the river looks clear. The first wildebeest bends down to drink. As it drinks, a crocodile breaks the surface and moves forward, barely making a ripple...

All animals must eat other living things, whether they eat plants or other animals. They need matter to build their bodies and energy to stay alive. Plants produce energy and matter by making food from sunlight, water, and air. Herbivores eat those plants, and predators eat other animals. This movement of energy and matter from one living thing to another is called a food chain. Small predators are often a food source for larger predators. But some predators are so big and powerful that no other animals prey on them. They are called apex predators. They sit at the top of a food web. Apex predators play a powerful role in every ecosystem on Earth. Word Wise Apex means "top" or "highest point."

The Great Hunters Apex predators can be found everywhere on Earth, from the tops of mountains to the bottom of the sea. They range from tigers to eagles, pythons to sharks, but they all have a couple of things in common. Most are carnivores— animals that eat only meat. Also, most apex predators are not picky eaters. They often eat dozens of different types of animals that are lower on the food chain. Most apex predators fall into one of the following groups: Big Cats All cats are excellent hunters— even your cute house cat. Big cats hunt everything from mice to hippopotamuses. Crocodilians, Crocodilians including crocodiles and alligators, are such effective hunters that their bodies and behavior have not changed in millions of years. Bears Not all bears are apex predators, or even carnivores. But the two largest—grizzly bears and polar bears—can strike bison, elk, seals, and even small whales that get too close to shore.

Dogs Many large dog species, such as wolves and wild dogs, are pack hunters. Working together, they can run down animals far larger than themselves. Birds of Prey Birds of prey hunt both fish and land animals. They eat live animals as well as carrion, or dead animals. Sharks Most sharks are small. But the largest sharks are unstoppable apex predators. They eat both fish and aquatic mammals such as seals. Toothed Whales Some whales have teeth and are apex predators. Orcas are efficient seal hunters. Sperm whales dive to the black depths to hunt giant squid. Squid and Octopuses Squid, along with their clever cousin the giant octopus are fierce deep-ocean hunters. Billfish Swordfish and their relatives are the fastest swimmers on Earth, making them expert predators.

Keystone Species All the organisms within a food web are dependent upon each other. As plant populations increase or decrease, herbivores have more or less food to eat. When herbivores are plentiful, predators have more animals to hunt. Apex predators have an especially powerful effect on food webs. One reason is that apex predators are often rare within an ecosystem. A mountain lion might be the only apex predator in its 250-square-kilometer (100 sq. mi.) territory. If anything happens to that mountain lion, no other species can replace it. The prey population will rise. Second, apex predators hunt many different kinds of prey. A mountain lion eats mice, birds, deer, elk, and more. These animals, in turn, affect all the grasses, insects, and trees that they eat.