What is the largest animal that starts with O?

The orca, or killer whale, is the largest O animal. Males typically measure 6–8 m (20–26 ft) and weigh more than 6 tonnes, and a few have been recorded at about 10 m (33 ft). On land, the ostrich is the tallest and heaviest living bird.

What sea animals start with O?

Ocean animals beginning with O include the octopus, orca, oyster, oarfish, ocean sunfish, opah, olive ridley sea turtle and ocellaris clownfish. Sea otters and oystercatchers also depend on the sea for their food.

What birds start with O?

Birds beginning with O include the ostrich, osprey, owl, oriole, oxpecker and oystercatcher. The ostrich is the largest living bird, while the osprey is a fish-eating raptor found on every continent except Antarctica.

Which animals that start with O are endangered?

All three orangutan species are Critically Endangered, and the okapi is Endangered. The ocean sunfish, olm, olive ridley sea turtle and Arabian oryx are listed as Vulnerable, while the onager and Eurasian oystercatcher are Near Threatened.

Is an orca a whale or a dolphin?

The orca is the largest member of the dolphin family, Delphinidae, even though it is commonly called the killer whale. Like all dolphins it is a toothed whale, so both names describe it correctly in a broad sense.

Animals That Start With O: Octopus, Okapi, Orca, Owl and More

Oarfish

The giant oarfish is the world’s longest bony fish, reliably recorded at about 8 m (26 ft) and possibly reaching 11 m (36 ft). It drifts through the open ocean in deep water and is rarely seen alive. Its long, ribbon-like silver body and red crest probably inspired many sea serpent stories. In Japan, oarfish are popularly believed to appear before earthquakes, but no such link has been shown.

Ocean sunfish

The ocean sunfish, or mola, is a huge, flattened fish that looks like a swimming head and drifts through temperate and tropical seas worldwide. Adults often weigh 250–1,000 kg (550–2,200 lb), and the heaviest bony fish on record is a related giant sunfish found off the Azores in 2021 at 2,744 kg (6,049 lb). A single female ocean sunfish was once found carrying an estimated 300 million eggs.

Ocelot

The ocelot is a medium-sized spotted wild cat of forests and scrub from southern Texas through Mexico and Central America to northern Argentina. Adults weigh about 7–15.5 kg (15–34 lb), about twice the size of a house cat. Every ocelot has its own pattern of spots and stripes, which researchers use to recognize individuals on camera-trap photos.

Ocellaris clownfish

The ocellaris clownfish is the orange-and-white reef fish made famous by the film Finding Nemo. It lives among the stinging tentacles of sea anemones in the eastern Indian Ocean and western Pacific, protected by a layer of mucus. All clownfish start life as males; when the breeding female of a group dies, the dominant male changes sex and takes her place.

Octopus

Octopuses are soft-bodied mollusks with eight arms, three hearts and blue, copper-based blood. There are about 300 species in oceans worldwide. They can change the color and texture of their skin in a fraction of a second and are known for solving puzzles and escaping from tanks. Learn how they differ from their relatives in octopus vs squid.

Okapi

The okapi lives only in the rainforests of the northeastern Democratic Republic of the Congo. Its striped legs look like a zebra’s, but its closest living relative is the giraffe, and the two are the only living members of the giraffe family. The okapi was formally described by scientists only in 1901 and is listed as Endangered.

Olive ridley sea turtle

The olive ridley is the most abundant sea turtle in the world and lives in warm waters of the Pacific, Indian and Atlantic oceans. It is famous for mass nesting events called arribadas, Spanish for “arrivals”, when many thousands of females come ashore together to lay eggs on beaches in Mexico, Costa Rica and eastern India. It is listed as Vulnerable.

Olm

The olm is a blind, pale salamander that lives in flooded caves of the Dinaric karst, from northeastern Italy and Slovenia to Croatia and Bosnia and Herzegovina. Its pinkish skin earned it the nickname “human fish”, and floods that washed olms out of caves once made people think they were baby dragons. One study estimated a maximum lifespan of over 100 years, and in experiments olms survived up to 10 years without food.

Onager

The onager, or Asiatic wild ass, is a sandy-colored wild relative of the horse that lives in the deserts and dry steppes of Asia, including Iran, Mongolia, China and India. It has never been domesticated. Hunting and competition with livestock have cut its range sharply since the early 20th century, and it is listed as Near Threatened.

Opah

The opah, or moonfish, is a large, round, silvery-red fish of the open ocean. In 2015, scientists showed that it is the only fish known to keep its whole body warmer than the surrounding water. Heat produced by its constantly flapping pectoral fins keeps its heart and brain warm, helping it hunt in cold, deep water.

Opossum

The Virginia opossum is the only marsupial found north of Mexico, ranging from Central America to southern Canada. Females carry their tiny young in a pouch and later on their backs. When badly frightened, an opossum may collapse and appear dead for minutes or even hours, an involuntary response that gave rise to the phrase “playing possum”. See possum vs opossum to untangle the names.

Orangutan

Orangutans are red-haired great apes that live in the rainforests of Borneo and Sumatra and spend most of their lives in the trees. Their name comes from Malay words meaning “person of the forest”. Females give birth only once every six to nine years, the longest gap of any great ape, and all three species, Bornean, Sumatran and Tapanuli, are Critically Endangered.

Orb-weaver spider

Orb-weavers are the spiders that build the classic round, wheel-shaped web. The European garden spider is a familiar example in late summer gardens. Darwin’s bark spider of Madagascar builds the largest known orb webs, with bridge lines spanning up to 25 m (82 ft) across rivers, and its silk is the toughest biological material ever tested.

Orca

The orca, or killer whale, is the largest member of the dolphin family and lives in every ocean. Males typically measure 6–8 m (20–26 ft), and their tall dorsal fin can be up to 1.8 m (6 ft) high. Different populations specialize in different prey, from salmon to seals, and pass on their own hunting techniques and calls from generation to generation.

Oriole

The name oriole is used for two unrelated groups of brightly colored birds. Old World orioles, such as the golden oriole of Europe, are tropical-looking yellow-and-black songbirds, while New World orioles belong to the blackbird family. The Baltimore oriole, the state bird of Maryland, weaves a hanging, sock-shaped nest high in a tree.

Oryx

Oryxes are desert antelopes with long, straight or gently curved horns. The Arabian oryx was declared extinct in the wild in 1972, but captive-bred animals were released from 1982, and in 2011 it became the first species ever to improve from Extinct in the Wild to Vulnerable. The scimitar-horned oryx made a similar comeback in Chad and was moved from Extinct in the Wild to Endangered in 2023.

Osprey

The osprey is a fish-eating bird of prey found on every continent except Antarctica. It hunts by plunging feet-first into the water. A reversible outer toe and spiny pads on its feet help it grip slippery fish, which it carries headfirst to reduce drag.

Ostrich

The ostrich of Africa is the tallest and heaviest living bird. Males stand 2.1–2.75 m (7–9 ft) tall and usually weigh 100–130 kg (220–290 lb). It cannot fly but can sprint at about 70 km/h (43 mph), faster than any other two-legged animal, and it lays the largest eggs of any living bird. The idea that ostriches bury their heads in the sand is a myth.

Otter

Otters are playful, semi-aquatic members of the weasel family; there are 13 species, found on every continent except Australia and Antarctica. The sea otter of the North Pacific has the densest fur of any animal, which keeps it warm without a layer of blubber. The giant otter of the Amazon can reach about 1.8 m (6 ft) including its tail.

Owl

Owls are mostly nocturnal birds of prey, with about 250 species found on every continent except Antarctica. They cannot move their eyes in their sockets, but they can turn their heads about 270 degrees. Soft, fringed edges on their flight feathers make their flight almost silent, and many species can find prey by sound alone.

Oxpecker

Oxpeckers are two species of African songbirds that spend their days riding on buffalo, giraffes, rhinos and cattle. They feed mainly on ticks and other parasites picked from the animals’ skin. Their partnership is not entirely helpful, however, because oxpeckers also peck at wounds and drink their hosts’ blood.

Oyster

Oysters are bivalve mollusks that live attached to rocks and to each other, forming reefs in shallow coastal waters. An eastern oyster can filter up to 190 liters (50 gallons) of water a day, which helps keep bays clean. Many oysters change sex during their lives, and the pearl oysters that produce most gem-quality pearls belong to a different family from the oysters people eat.

Oystercatcher

Oystercatchers are noisy black-and-white or all-black shorebirds with long, bright orange-red bills. The Eurasian oystercatcher feeds mainly on cockles, mussels and worms, opening shells by hammering or by stabbing between the two halves. It is a familiar sight on European coasts and is listed as Near Threatened.