Animals live in virtually every environment on Earth, from tropical rainforests and open ocean to underground caves and the deepest ocean trenches. These environments, called habitats, provide the food, shelter, water, and space each species needs to survive. About 71% of Earth’s surface is covered by water, making oceans the single largest habitat on the planet. The remaining land is divided among forests, deserts, grasslands, and frozen tundra, each home to its own community of wildlife.
Land Habitats: Eight Major Biomes
Earth’s land surface is organized into eight major biomes, each defined by its climate, plant life, and the animals adapted to it.
Tropical rainforests sit near the equator and receive heavy rainfall year-round. Their layered canopy, from forest floor to treetops, creates countless niches for animals. Monkeys, tree frogs, parrots, jaguars, and millions of insect species rely on the dense vegetation for food and shelter. The highest concentrations of mammal species on the planet are found in the Amazonian lowlands, the Andes, East Africa, and Southeast Asia.
Savannas are warm grasslands dotted with scattered trees, found across sub-Saharan Africa, parts of South America, and northern Australia. Large grazers like zebras, wildebeest, and elephants roam these open landscapes alongside predators such as lions and cheetahs.
Subtropical deserts cover vast stretches of North Africa, the Middle East, and the American Southwest. Most desert animals have adapted to a nocturnal lifestyle, spending scorching daytime hours beneath the ground and emerging at night to hunt or forage. Reptiles, scorpions, and small rodents are especially well represented.
Temperate grasslands include the North American prairies, South American pampas, and Central Asian steppes. The American bison is one of the most iconic grassland animals, once numbering in the tens of millions across the prairies. Burrowing animals like prairie dogs and ground squirrels are also common, since the flat terrain offers few places to hide above ground.
Temperate forests experience four distinct seasons. Thick leaf litter on the forest floor provides habitat for invertebrates and the birds, salamanders, and small mammals that feed on them. Deer, foxes, black bears, and woodpeckers are typical residents.
Boreal forests (also called taiga) stretch across Canada, Scandinavia, and Russia in a wide band south of the Arctic. Moose, wolves, lynx, and migratory songbirds inhabit these cold, conifer-dominated woodlands.
Arctic tundra is Earth’s coldest biome, with permafrost underlying treeless plains. Caribou, Arctic foxes, snowy owls, and lemmings survive here through thick insulation, seasonal migration, or burrowing beneath the snow.
Chaparral is a shrubby, Mediterranean-climate biome found in coastal California, parts of Chile, and southern Europe. Fire-adapted plants support lizards, rabbits, coyotes, and various bird species.
Ocean Habitats: Surface to Seafloor
The ocean is divided into layers based on depth, and animal life changes dramatically as you descend. The sunlight zone extends from the surface down to about 200 meters (660 feet) and is where most familiar marine life exists: tuna, dolphins, sea turtles, sharks, and coral reef fish all depend on the light that fuels the food chain here.
Below that, the twilight zone (200 to 1,000 meters) receives only faint light. Animals here, including lanternfish and certain squid, often produce their own light through bioluminescence. Their eyes tend to be large and point upward, helping them spot the silhouettes of prey against the dim glow above.
The midnight zone (1,000 to 4,000 meters) is completely dark. Sperm whales dive to this depth to hunt giant squid. The few fish that live here are often small, with slow metabolisms suited to a world where food is scarce. Deeper still, the abyssal zone (4,000 to 6,000 meters) supports only a handful of highly specialized creatures under crushing pressure. The deepest fish ever recorded was found in the Puerto Rico Trench at 8,372 meters (about 27,460 feet).
Freshwater: Rivers, Lakes, and Wetlands
Freshwater habitats make up a tiny fraction of Earth’s water but support a remarkable variety of life. Fish are the animals most closely associated with these environments. Trout, bass, and bluegill spend their entire lives in the same lake or river. Large predators like crocodiles and anacondas sit at the top of many freshwater food chains.
Marshes and wetlands, where shallow water mixes with grasses and reeds, attract a different set of species. Hippos, otters, water buffalo, and muskrats all depend on marshy areas. Wetlands also serve as critical breeding grounds for amphibians like frogs and salamanders, and as stopover points for migrating birds.
Underground and Cave Habitats
Some animals live their entire lives in total darkness beneath the Earth’s surface. More than 7,500 species of cave-dwelling animals (called troglobites) have been discovered, and most are invertebrates like insects and crustaceans. Many have lost their pigment entirely and have no functional eyes, having evolved over millennia in environments where vision is useless.
These creatures are famous for their patience. They have extraordinarily slow metabolisms, with some able to survive for years without eating. A crayfish found in Alabama caves can live up to 175 years and reproduce for 100 of them. Slovenia is home to a blind salamander known as the olm, and Hawaii’s Kaua’i cave wolf spider is completely eyeless yet tracks down prey without a web. One species of giant cave centipede catches bats in mid-flight and devours them whole.
Deep-Sea Vents: Life Without Sunlight
Hydrothermal vents on the ocean floor support thriving communities in conditions that seem impossible for life: superheated, chemical-laden water in total darkness. Instead of relying on sunlight, animals here depend on bacteria that convert toxic hydrogen sulfide into energy.
Giant clams at these vents have evolved a clever workaround. They extend their foot down into crevices that release sulfide-rich water while their gills remain bathed in oxygen-rich seawater from above. Their blood contains a specialized protein that binds to the toxic sulfide and carries it safely to symbiotic bacteria in their gills, which use it as fuel. Mussels at vents have retained the ability to filter-feed like their shallow-water relatives but also host dense colonies of bacteria in their gills. Tube worms absorb sulfide directly through their body walls. These different strategies allow large animal communities to flourish in habitats that would be lethal to most life.
Cities as Animal Habitat
Urban environments are increasingly important habitats. A global study spanning cities from New York to Nairobi and Moscow to Melbourne found that successful urban wildlife tends to share a few key traits: smaller body sizes that help them navigate tight spaces, and a willingness to eat a wide variety of foods. The image of a crow eating a slice of pizza captures this generalist approach well.
Different groups use cities in different ways. Birds and bees tend to operate from a home base, venturing out to find food and returning. Reptiles are more likely to be site specialists, sticking to a single patch of resources. Bats are true generalists, finding food almost anywhere in the urban landscape. Raccoons, rats, pigeons, peregrine falcons, and coyotes have all established permanent populations in major cities worldwide.
Animals That Use Multiple Habitats
Many animals don’t stay in one habitat. Migratory shorebirds travel enormous distances between breeding grounds on Arctic tundra and wintering grounds on coastal or inland wetlands near the equator and into the southern hemisphere. Even on a single day, these birds switch between intertidal mudflats for feeding at low tide and higher ground for resting at high tide.
Habitat switching happens at smaller scales too. Some owls roost in forests during the day and hunt over grasslands at night. Black-headed gulls alternate between land and sea depending on tide-driven changes in prey availability. These patterns mean that protecting a single habitat often isn’t enough. An animal’s survival can depend on the health of two, three, or more completely different environments linked across its annual cycle.