This page includes all animals that start with the letter O that we plan to cover on Fact Animal. As we publish new content, each of these animals will be linked to their dedicated profile fact pages.
From the Ocelot to Otter, read extraordinary facts about animals beginning with the letter O.
O
Oak Titmouse
Oak Toad
Oarfish
Oberhasli Goat
Oberlander Horse
Oblique-banded Sweetlips
Oblong Turtle
Ocean Perch
Ocean Sunfish
Ocean Whitefish
Oceanic Dolphins
Oceanic Puffer
Oceanic Whitetip Shark
Ocellated Turkey
Ocelot
Octopus
Odonata
Oedipina
Oenpelli Python
Ogcocephalidae
Ogre-Faced Spider
Oilfish
Okapi
Okarito Kiwi
Old English Sheepdog
Old House Borer
Old Squaw
Old World Flycatchers
Old World Monkeys
Old World Porcupines
Old World Rats
Old World Swallowtail
Olde English Bulldogge
Oleander Hawk Moth
Olingo
Olios
Olive Baboon
Olive Crescent Moth
Olive Python
Olive Sea Snake
Olive Woodpecker
Olive-backed Oriole
Olive-backed Pipit
Olive-backed Sunbird
Olive-backed Thrush
Olive-faced Flatbill
Olive-Flanked Ground Robin
Olive-green Tyrannulet
Olive-headed Lorikeet
Olive Ridley Sea Turtle
Olive-throated Parakeet
Olive-tree Warbler
Olive-winged Bulbul
Olm
Olympic Marmot
Onagadori Chicken
Onager
Opahs
Opaleye
Oncilla
Opossum
Oranda Goldfish
Orange Baboon Tarantula
Orange Lungless Spiders
Orange Roughy
Orange Spider Wasp
Orange-Headed Tanager
Orange-Crowned Warbler
Orange-Throated Whiptail
Orangutan
Orb Weaver
Orchard Oriole
Orchid Dottyback
Orchid Mantis
Oregon Spotted Frog
Oribi
Oriental Cockroach
Oriental Dwarf Kingfisher
Orinoco Crocodile
Ornate Bichir
Ornate Box Turtle
Ortolan Bunting
Oscar
Osprey
Ostracod
Ostrich
Otter
Otterhound
Ovenbird
Owl
Owl Butterfly
Owlfly
Ox
Please see our Animal A-Z list for animals that start with different letters.
Animal Names That Start With O
Read on for an overview of each of the animals listed above that begin with the letter O.
Animals Beginning with O
Oak Titmouse
The Oak Titmouse is not a tree, mammary or a rodent. Bafflingly, it’s a small, grey songbird found in oak woodlands of western North America.
Fun Fact: These sweet little birds nest in more or less any suitable cavity they can find, often re-using old woodpecker holes.
Oak Toad
The Oak Toad is a small amphibian native to the southeastern United States, looking sort of flattened, with a stripe running from its nose down its back.
Fun Fact: This is. Very small toad, growing up to a maximum of around 3cm long. One of the smallest toads in the world and the smallest in North America.
Oarfish
The Oarfish is an elusive, deep-sea fish known for its ribbon-like body and silver scales. It lives in both temperate and tropical waters, but it is hardly ever spotted.
Fun Fact: Oarfish are one of the longest-known species of fish, with some individuals reaching lengths of up to 17 meters (56 ft).
Oberhasli Goat
The Oberhasli Goat is a Swiss dairy breed known with a beautiful bay coat and black markings.
Fun Fact: This goat’s colouration is known as “chamoisée” because people say it resembles the Alpine goat-antelope, the chamois. But the goat is actually even better looking.
Oberlander Horse
The Oberlander Horse is an Austrian draught horse, known for its strength, endurance, and versatility in mountainous habitats.
Fun Fact: The Oberlander Horse is actually considered indigenous to the Central Alpine region of Europe, having originated from almost 4,000 m above sea level.
Obi Island Snake-necked Turtle
Oblique-banded Sweetlips
The Oblique-banded Sweetlips is a moderately kissable marine fish found in coral reefs of the Indo-Pacific region, covered in striking bands of yellow, black, and white.
Fun Fact: Oblique-banded Sweetlips are named for their Angelina Jolie-like fleshy lips that become increasingly swollen as they age.
Oblong Turtle
The Oblong Turtle is a side-necked turtle species native to Southwestern Australia. As the name suggests, it’s sort of a flattened oval shape with a very long neck.
Fun Fact: Oblong Turtles are known to be remarkably vocal for a turtle, with a recorded vocal repertoire of 17 categories.
Ocean Perch
The Ocean Perch is a large species of rockfish found in cold waters of the North Sea and Western Atlantic, it has vibrant red/orange colouration and spiny dorsal fins.
Fun Fact: The Ocean Perch is not a true perch, and belongs to the family Scorpaenidae, which contains some of the most venomous fishes in the world.
Ocean Pout: The Ocean Pout is an eel-like, bottom-dwelling fish species found in the North Atlantic.
Fun Fact: Ocean Pouts contain a unique antifreeze protein in their blood, allowing them to survive in frigid waters where other fish species cannot thrive.
Ocean Sunfish
The Ocean Sunfish, or Mola Mola, is the heaviest known bony fish in the world, found in temperate and tropical oceans globally, iconic for its flattened body and peculiar bemused expression.
Fun Fact: This fish undergoes one of the most extraordinary transformations over its lifetime: from a tiny larva to an adult 60,000,000 times its mass.
Ocean Whitefish
The Ocean Whitefish is a marine fish species found along the rocky Eastern Pacific coast of North America. It’s a pale brown, with a white abdomen.
Fun Fact: Ocean Whitefish are important predators of small crustaceans, and can live up to 13 years.
Oceanic Dolphins
The Oceanic Dolphins, or Delphinidae, are a large family of around forty species of highly intelligent marine mammals. These powerful predators range from the 1.5m Hector’s dolphin to the 8.2m Orca.
Fun Fact: Dolphins make up the majority of the toothed whale lineage, separated from the baleen whales around 39 million years ago.
Oceanic Puffer
The Oceanic Puffer, also known as the Oceanic Pufferfish, is a species of pufferfish found in tropical and subtropical oceans worldwide. It’s famous for being inflatable and extraordinarily toxic.
Fun Fact: The Latin name for this species, Lagocephalus lagocephalus, translates to “rabbit head, rabbit head.
Oceanic Whitetip Shark
The Oceanic Whitetip Shark is a large pelagic shark species found in warm oceanic waters around the world, named for its long, white-tipped dorsal fin and is known for being an aggressive hunter, prone to feeding frenzies.
Fun Fact: Oceanic Whitetip Sharks are known for their association with shipwrecks and are often among the first to arrive at the scene, earning them the nickname “sea dogs” among sailors and divers.
Ocellated Turkey
The Ocellated Turkey is a species of fowl native to the Yucatán Peninsula in Mexico and parts of Guatemala and Belize. It’s a smaller and much more colourful version of the unfortunate Christmas variety.
Fun Fact: Ocellated Turkeys roost in trees rather than on the ground, using their strong legs and feet to grasp branches and evade jaguars.
Ocelot
The Ocelot is a gorgeous wild cat native to the Americas. Its fur is dappled with a striking rosette pattern resembling that of a small jaguar.
Fun Fact: Ocelots are extremely skilled climbers and proficient hunters, preying on a variety of small mammals, birds, and reptiles, so play a significant role in top-down selective pressure.
Octopus
Octopuses are one of the most intelligent animals in the ocean, making up 300 species of marine cephalopods, all of which are expertly camouflaged hunters.
Fun Fact: Octopuses are short-lived and solitary animals but exhibit a relatable level of curiosity and mischief as a result of their independently evolved smarts. These clearly-sentient molluscs are more closely related to snails than any mammal.
Odonata
Odonata is an ancient order of insects comprising dragonflies and damselflies, characterised by their large, transparent wings, elongated bodies, and voracious predatory behaviour.
Fun Fact: Dragonflies are the most agile flying animals, able to hover, dart, and even fly backwards. This makes them one of the most successful hunters in the animal kingdom.
Oedipina
Oedipina, commonly known as lungless salamanders, are small, elongated amphibians found in Central and South America, often dwelling near freshwater streams and rivulets.
Fun Fact: Oedipina salamanders are among the few amphibians that undergo direct development, meaning their eggs hatch directly into miniature versions of adults, skipping the aquatic larval stage seen in other amphibians. But without lungs, they have to breathe through their skin!
Oenpelli Python
The Oenpelli Python, also known as the Oenpelli Rock Python, is a large python endemic to northern Australia, inhabiting rocky outcrops, woodlands, and savannas.
Fun Fact: These pythons are able to change their skin colour, appearing lighter in the daytime and darker at night, presumably not just because of the ambient light.
Ogcocephalidae
Ogcocephalidae is a family of ray-like anglerfish or batfish characterized by their flattened bodies, modified pectoral fins, and fleshy appendages used as lures to attract prey.
Fun Fact: Some species in this family can be found in waters as shallow as 200m deep, pottering about on fleshy limbs as if walking along the sea floor. Their fins are so adapted to walking that they’re clumsy swimmers.
Ogre-Faced Spider
The Ogre-faced Spiders are a genus of net-casting spiders, recognizable for their extremely long front limbs and enormous forward-facing eyes.
Fun Fact: These are some of the most ominous ambush spiders, hanging vertically, motionless, above a spun net of silk, waiting for a victim to pass underneath. Their eyes are 2000 times more receptive to light than a human’s.
Oilfish
The Oilfish is a species of large, snake mackerel with big teeth and rough scales from temperate and tropical waters all over the world.
Fun Fact: This fish is known to have a laxative effect on people who eat it, but this doesn’t appear to have deterred the Japanese, who commonly sell it as “white fish”.
Okapi
The Okapi, also known as the forest giraffe is a rare and elusive giraffid native to the dense forests of the Democratic Republic of the Congo in Central Africa. It’s smaller than a giraffe with a shorter neck and striped back legs.
Fun Fact: This is the only “other” member of the giraffe family and was entirely unknown to the Western world until the 20th Century.
Okarito Kiwi
The Okarito Kiwi, also known as the Rowi, is a small, flightless bird native to Western New Zealand. It’s a pretty standard Kiwi-looking bird, with only about 600 in its entire population.
Fun Fact: Originally thought to be a population of the Southern brown Kiwi, this species was given its recognition as recently as 2003.
Old English Sheepdog
The Old English Sheepdog, also known as the Dulux dog, is a large and fluffy herding dog breed originating from England. These smart and gentle dogs look a bit like a freshly cleaned paint roller.
Fun Fact: This breed has a double coat, with a water-resistant undercoat, giving them a range of colours including greys, blues, blacks and silver.
Old House Borer
The Old House Borers are a genus of wood-boring longhorn beetles native to Europe but now found worldwide, infests and damage wooden structures such as homes and furniture.
Fun Fact: This genus has spread all over the world, travelling inside imported furniture, and is known in South Africa as the Italian beetle for this reason.
Old Squaw
The Old Squaw is another name for the Long-tailed Duck, a very pretty little sea duck species found in the upper reaches of the Northern Hemisphere. It has a long tail feathers and painted plumage.
Fun Fact: These ducks are great at diving, able to fully submerge themselves in the hunt for crustaceans, small fish and molluscs.
Old World Flycatchers
The Old World Flycatchers is a diverse family of 350+ small to medium-sized passerine birds found across Europe, Africa, and Asia. They’re named for their insect-catching behaviour and often have very pretty, melodious songs.
Fun Fact: These unassuming little birds are hugely significant predators of insects, keeping populations under control by catching their prey on the wing.
Old World Monkeys
Old-world monkeys are a diverse group of around 140 primate species belonging to the family Cercopithecidae, distributed throughout Africa, Asia, and parts of Europe, characterized by their downward-facing nostrils.
Fun Fact: Old-World monkeys are more closely related to modern apes than New World monkeys. Unlike in the latter group, there are no species of Old-World monkey with prehensile tails.
Old World Porcupines
The Old World Porcupines are a family of large and prickly rodents, spread out from Southern Europe, through much of Africa and Asia. These differ significantly from the New World versions, despite looking similar.
Fun Fact: In contrast to the New World porcupines, whose spines are interspersed with bristles, these guys have clusters of spines, all of which are barbed and can snap off in your face.
Old World Rats
Murinae is a subfamily of rats and mice from the Old World. The infamous black and brown rats are members of this subfamily, which spans Africa, Asia and Europe natively, but more or less everywhere else since the dawn of shipping.
Fun Fact: This subfamily of rodents is bigger than almost every family of mamma and even all mammal orders except bats. The only bigger families are the one that contains them (obviously), the Muridae, and the hamster family Ciricetidae.
Old World Swallowtail
The Old World Swallowtail, Is a large, beautiful butterfly found across Europe, Asia, and North Africa, with black and yellow wings adorned with blue and red markings and the characteristic swallowtail-shaped appendage at the base.
Fun Fact: The caterpillars of the Old World Swallowtail mimic the appearance of bird droppings as a form of camouflage, helping them evade predators.
Olde English Bulldogge
The Olde English Bulldogge is a muscular, medium-sized dog breed developed in the United States and bred to resemble the historical Bulldogges of England: with a more athletic build and fewer health issues.
Fun Fact: This abomination of language and back-breeding is actually an interesting candidate for genetic studies involving the breeding out of common “purebred” defects as a result of the inbreeding seen in domestic dogs.
Oleander Hawk Moth
The Oleander Hawk Moth, also known as the Army Green Moth, is a stunning, and large moth species found across Asia, Africa and Hawaii. It comes in the classic giant-headed hawkmoth caterpillar and a striking green camo adult variety.
Fun Fact: These incredible moths are migratory, residing permanently in Africa and Asia, but migrating into Southern and Eastern Europe during the Summer.
Olingo
The Olingo is a small arboreal mammal native to Central and South America, looking a bit like a cross between a demonic cat and a galago, with a slender body, long tail, and large, nocturnal eyes.
Fun Fact: Olingos procyonids, and close relatives of the racoons. Their closest relatives are the coatis.
Olios
Olios is a large genus of spiders belonging to the huntsman family, Sparassidae. They’re found almost anywhere hot and make up around 160-250 species. They’re usually light to dark brown.
Fun Fact: Like all huntsman spiders, Olios spiders are intelligent, active hunters with keen eyesight.
Olive Baboon
The Olive Baboon is a large and widespread species of baboon found in various habitats across 25 countries in Africa.
Fun Fact: Olive Baboons have rings of yellow-brown and black colouration in their hairs which give them a green-grey appearance from a distance, which is where they get their name.
Olive Crescent Moth
This is a rare species, resident in just a few scattered deciduous woodland areas in the south of England, but dotted around most of Europe, Siberia and Northern China. It’s the lightest moth in the Erebidae family.
Fun Fact: This is the only member of the Trisateles genus, yet an important predator of oak, beech, hornbeams and bramble species.
Olive Python
The Olive Python is a large python native to Northern and Western Australia. The high concentration of scales on its back gives it a smoother appearance than many pythons.
Fun Fact: Olive pythons are Australia’s third biggest snake, reaching more than 4 meters in length.
Olive Sea Snake
The Olive Sea Snake is a venomous marine snake found in the warm coral reef waters of the Indian and Pacific Oceans. It’s recognizable for its olive-green to brownish colouration and flattened tail.
Fun Fact: These snakes have some of the most toxic venom known to man yet are also one of the least likely to bite a person. They never leave the water and are known to curiously approach divers.
Olive Woodpecker
The Olive Woodpecker is native to Central, Eastern and Southern Africa. It has olive-green plumage and a distinctive red crown in males, often seen doing what woodpeckers do: foraging on trees for insects.
Fun Fact: These birds are unusual for woodpeckers, in that they lack the barring, spotting, and streaking found in most species.
Olive-Backed Oriole
The Olive-backed Oriole is a small, fairly drab bird species found in Australia and south-central New Guinea.
Fun Fact: This bird has a more colourful close relative called the Green oriole, but what it lacks in vibrance, it makes up for in adaptability to a wider range of habitats than its cousin.
Olive-backed Pipit
The Olive-backed Pipit is a migratory bird species found across Asia and Europe, recognised by its olive-brown upperparts, streaked breast, and habit of wagging its tail while foraging for insects and seeds on the ground.
Fun Fact: These tiny birds are remarkably tough animals, breeding at altitudes of up to 4,500 meters in Nepal.
Olive-backed Sunbird
The Olive-backed Sunbird, or Garden sunbird, is a small passerine bird native to the Philippines. It has an olive-brown head and back, a yellow breast and a curved, nectar-feeding beak.
Fun Fact: Sunbirds like this play a similar role to hummingbirds in the New World: harvesting nectar and pollinating plants. But this species is also known to take insects on occasion.
Olive-backed Thrush
The Olive-backed Thrush is a migratory bird species found in coniferous woods in North America, breeding as far South as Costa Rica.
Fun Fact: Olive-backed Thrushes are characteristically thrushlike, with a lack of colour juxtaposed against a beautiful set of calls.
Olive-faced Flatbill
The Olive-faced Flatbill is a species of New World flycatcher native to South America, characterized by its olive-green plumage, distinct facial markings, and short, pointed beak adapted for catching insects.
Fun Fact: This little predator does better in secondary forests, and is commonly found in the riparian woodland and at the forest edge in Western Amazonia.
Olive-Flanked Ground Robin
The Olive-Flanked Ground Robin is native to the tropical montane forests of Mozambique and Malawi. Like the common red breast, it’s an Old-World flycatcher with a rufous neck and breast in males.
Fun Fact: This tiny bird has an equally tiny range, and there’s still not a lot of information available on it, but there are concerns for its safety as the forests it relies on are being reduced.
Olive-green Tyrannulet
This is a species of tyrant flycatcher found in South America, recognized by its olive-green plumage, pale yellow underparts, and habit of perching in the canopy and sallying out to catch insects in mid-air.
Fun Fact: These are members of the largest bird family in the world, with more than 400 species spanning the Americas.
Olive-headed Lorikeet
The Olive-headed Lorikeet is sometimes called the Perfect Lorikeet, and it’s hard to argue with a bird this pretty. It lives in forests, woodland and in cultivated lands in Timor and the nearby islands.
Fun Fact: These are popular in the pet trade and in menageries as they’re intelligent, tough little parrots with a beautiful plumage.
Olive ridley sea turtle
This marine Turtle species is distributed across the world’s warm and tropical oceans, recognized by and named for its olive-green carapace.
Fun Fact: These are petite turtles, growing to a mere 60cm across, making them the second-smallest species of sea turtle after the Kemp’s ridley.
Olive-throated Parakeet
This is one of countless green parakeets that need differentiating from one another. In this instance, it has a distinctive olive-green patch that covers its throat and belly. Commonly found in tropical lowlands in Central and South America.
Fun Fact: These are tough and highly social birds, capable of swarming agricultural lands and are consequently considered a crop pest in some places.
Olive-tree Warbler
The Olive-tree Warbler is a pretty average-looking migratory Old World warbler from Southern Europe and Africa. It’s the largest in the Hippolais genus and has a powerful beak and heavy legs.
Fun Fact: Olive-tree Warblers are adept at mimicking the calls of other bird species, often in a snarky, mocking tone.
Olive-winged Bulbul
This relatively plain-looking bulbul has deep red eyes to remind you exactly what it is. They’re spread out all the subtropical or tropical moist lowland forests of Southeast Asia and make a recognizable chirpy, grating song.
Fun Fact: Olive-winged Bulbuls are widespread eaters of insects and seeds, making them highly ecologically significant.
Olm
The Olm, also known as the Proteus, is a unique aquatic salamander species endemic to subterranean freshwater limestone caves in the Balkans. It’s a wormlike amphibian, locally called “human fish” on account of its fleshy, pale appearance.
Fun Fact: These foot-long slippery amphibians are Europe’s only exclusively cave-dwelling vertebrate. They were traditionally thought to be cave dragon babies.
Olympic Marmot
The Olympic Marmot is a species of large ground-dwelling squirrel found only in Washington State, USA.
Fun Fact: Male Olympic marmots are 23% larger than females, which is the largest sexual dimorphism found in any marmot species.
Onagadori Chicken
The Onagadori Chicken is a rare and ornamental breed of domestic fowl native to Japan, bred for its exceptionally long tail feathers, which can reach lengths of up to 12 meters in mature males.
Fun Fact: The ridiculous length of this beautiful bird’s back end means that breeders have to construct special houses for them, well off the ground.
Onager
The Onager, also known as the Asiatic Wild Ass, is a species of large and well-shaped ass native to the arid regions of southwest Asia. It has a sandy-brown coat, a black dorsal stripe, and a distinctive white belly.
Fun Fact: Like all of their kind, Onagers are badasses, able to tolerate extremes in temperature and diverse habitats.
Opahs
The Opah, also known as the Moonfish or Sunfish, is a unique and small family of deep-sea fish found in oceans worldwide. They are unrelated to the Mola sunfish, though almost as weird-looking.
Fun Fact: One species is the only fish known to be able to maintain its entire body temperature at a steady 5 °C above the surrounding water.
Opaleye
The Opaleye, or Rudderfish, is a very pretty species of sea chub found in coastal waters of the Atlantic Ocean. It’s got iridescent blue-green colouration and a distinctive set of two to six white spots on its back.
Fun Fact: As they age, many individuals grow new kinds of teeth, exchanging their tricuspid teeth for simpler ones in adulthood.
Opossum
The Opossum is a fantastically adaptable omnivorous marsupial native to the Americas. Its distinctive long, rat-like tail, pointed snout, and remarkable ability to “play dead” when threatened, make it a well-known critter across its range.
Fun Fact: Opossums and possums are totally different animals! The latter are arboreal Australasian marsupials from a totally different order.
Oranda Goldfish
The Oranda Goldfish is a fancy goldfish breed originating from China and Japan, prized for its distinctive hood or “wen” that grows on the top of its head that makes it look like it’s pushing a raspberry.
Fun Fact: The raspberries on their heads are no mean feat to develop. Juveniles spend up to two years growing them and some cover the eyes to the point of blinding the poor fish.
Orange Baboon Tarantula
The Orange Baboon Tarantula is a species of large, colourful baboon spider native to much of Africa. As the name suggests it’s strikingly orange in colour, and is sometimes known as the Mombasa golden starburst tarantula.
Fun Fact: Unlike most New World tarantulas, this one is quite defensive and packs a punch. Bites are said to be extremely painful.
Orange Lungless Spiders
The orange lungless spiders are top contenders for “Least imaginative name”, but are interesting, nonetheless. They are two related genera of a much larger family of spiders related to cellar spiders. They’re orange, and they don’t have lungs.
Fun Fact: All members of this family are equally lungless, it’s only these two that get the common name. In some species, the number of eyes will increase when the spiderling changes its skin as it grows towards adulthood.
Orange Roughy
This is a fish with a number of relatively insulting names. Also called the red roughy or slime perch, it is actually quite an ugly fish that looks like it’s pink with confused rage. Luckily, it’s rarely seen as it lives in deep waters.
Fun Fact: Orange Roughy is one of the longest-lived fish species, with individuals known to live up to 200 years.
Orange Spider Wasp
This is a large and terrifying spider-hunting wasp from Australia. At 3.5cm, their main source of prey is huntsman spiders, which they paralyse and lay eggs into for their larvae to eat. Unsurprisingly, their sting is said to be “Shockingly powerful”.
Fun Fact: These horrific killers actually feed on nectar as adults. The whole ‘eaten alive’ thing is just for their grubs.
Orange-Headed Tanager
This sounds like it got its name from ‘50s comic book slang for male genitals but it’s actually a small, finch-like omnivore from South America.
Fun Fact: These little tanagers thrive in successional forests, which are the young, transitional growth areas between grassland and full-blown forests. So, they thrive in previously-damaged habitats!
Orange-Crowned Warbler
The Orange-Crowned Warbler spends its time across much of western and northern North America, and east across Canada. It eats insects when they are plentiful and moves more to berries during Winter.
Fun Fact: Despite their name, many, if not most of these birds have an almost indistinguishable crown.
Orange-Throated Whiptail
This small whiptail lizard is native to the US and Mexico, and sports a black or brown body streaked with five or six creamy lines down its back.
Fun Fact: Like many whiptails, this species is highly variable in colour. The young have stunning cobalt blue legs, and the adults may sometimes have orange bellies and tails. Females appear to get an orange jaw when pregnant.
Orangutan
The Orangutan is a large arboreal ape species native to the rainforests of Borneo and Sumatra, instantly recognizable for its distinctive red-orange fur, long arms, and inquisitive, gentle nature.
Fun Fact: Orangutans are highly intelligent, and are the heaviest arboreal animal. They likely evolved to stay in trees as a result of all the tigers that used to live underneath them.
Orb Weaver
Orb Weavers are a diverse group of familiar spiders belonging to the family Araneidae. These are the spiders that sit in the middle of intricate, wheel-shaped webs, cast between branches.
Fun Fact: There are over 3000 species of orb weaver, ranging in size from the pinhead Neoscona to the terrifyingly large Nephilla.
Orchard Oriole
The Orchard Oriole is a small, omnivorous migratory bird species found in North and Central America. Males have orange bodies and dark heads with black heads and wings.
Fun Fact: These are the smallest of the 108 known species of Icterid bird, and change colour dramatically from juvenile to adult.
Orchid Dottyback
The Orchid Dottyback is a 6cm long bright purple fish from the Red Sea. Its vibrant colour makes it popular in aquariums.
Fun Fact: These fish are said to be the most social and tolerant of the dottybacks and are a hardy species in tropical tanks.
Oregon Spotted Frog
Also known as the “Precious Frog”, the Oregon Spotted Frog is a medium-sized species native to the Pacific Northwest region of North America. They grow up to 10cm long and look typically frog-like.
Fun Fact: These frogs change colour as they age, beginning as a light shade of brown and growing redder as they get older.
Oribi
The Oribi is a small antelope species found in savannas and grasslands across Eastern, Western and Southern Africa. It’s a petite bovid, with reddish-brown fur, and graceful leaps.
Fun Fact: A significant social behaviour of this antelope is a ceremonial dung midden, in which family members make and maintain a pile of their own poo.
Oriental Cockroach
The Oriental Cockroach is a large and common household terror, at 3cm long with a shiny, black body.
Fun Fact: Despite their name, these cockroaches are endemic to the Crimean peninsula, and have spread throughout the world via human globalization.
The Oriental Dwarf Kingfisher
Also known as the Black-backed kingfisher, this is a colourful bird species found in the forests of Southeast Asia with a beautiful vibrant plumage of oranges, reds and blues.
Fun Fact: While their name suggests a diet rich in fish, this species spends a lot of time hunting in terrestrial habitats, feeding on lizards, insects, spiders, and other invertebrates.
Orinoco Crocodile
This crocodile species can only be found in the Orinoco River basin in Venezuela and Colombia. It was hunted almost to extinction for its skins and is now one of the most endangered crocodilians.
Fun Fact: Orinoco Crocodiles are the largest crocodilian in the Americas, and one of the largest in the world, with some individuals reported to have weighed up to 900kg.
Ornate Bichir
The Ornate Bichir is a black and yellow freshwater fish species native to the rivers and lakes of West and Central Africa. It has a highly elongated body and grows up to about 60cm long.
Fun Fact: Ornate Bichirs have a primitive pair of lungs in addition to gills, allowing them to breathe air at the water’s surface and survive in poorly oxygenated environments for extended periods.
Ornate Box Turtle
The Ornate Box Turtle is a species of terrestrial turtle found in the central United States, named for its patterns of pretty yellow lines that radiate from the centre of its shell.
Fun Fact: Ornate Box Turtles are known for their longevity, with some individuals living up to 50 years or more in the wild when given optimal habitats and conditions.
Ortolan Bunting
The Ortolan Bunting is a small, finch-like passerine bird species found in Europe and parts of Asia. It has a pink beak and a yellow throat.
Fun Fact: In France, the Ortolan Bunting has been historically hunted for culinary purposes, with a controversial tradition involving capturing, fattening, and consuming the birds whole.
Oscar
The Oscar is a beautiful and popular freshwater fish from South America with colouration that varies from dappled cream to smouldering volcano and is understandably popular in aquariums.
Fun Fact: These fish can lay up to 2,000 eggs, which they place on meticulously cleaned horizontal surfaces that the mating pair work together to prepare.
Osprey
The Osprey is a large and powerful bird of prey found worldwide near bodies of water, recognized for its distinctive white head, brown wings, and expert fishing skills.
Fun Fact: The osprey is unusual in that it is a sole living species that occurs nearly worldwide. It is the most widely distributed raptor after the Peregrine falcon.
Ostracod
Ostracods, commonly known as seed shrimps, are an entire class of small aquatic. crustaceans are found worldwide, defined by their bivalve-like carapaces and small size. The largest is 8mm long.
Fun Fact: Ostracods are one of the most abundant groups of crustaceans, and the most commonly represented in the fossil record. They date back over 500 million years.
Ostrich
The Ostrich is the world’s largest bird species and the most powerful of the remaining ratites. They’re native to Africa and have thick, long necks and immensely strong legs.
Fun Fact: Ostriches are one of the fastest animals on the savanna, capable of running up to a very nice 69 km/h.
Otter
Otters are semi-aquatic mustelids, popular for their playful behaviour, agile swimming abilities and dense fur coats that help them stay warm in cold water and make them look adorable.
Fun Fact: Otters are known to use tools, such as rocks, to crack open shellfish and crustaceans. Some also hold hands while sleeping in the water so they don’t drift apart.
Otterhound
The Otterhound is a large, scruffy, and floppy-eared dog breed from England that weighs up to about 50 kg.
Fun Fact: Otterhounds were historically bred specifically for hunting otters, which were considered pests to fish ponds in medieval England. When the otters ran out in the 20th century, they became a bit redundant and now there are only 600 otterhounds left.
Ovenbird
The Ovenbird is a large wood warbler with the colouration of a thrush. They’re migratory birds from North and South America,
Fun Fact: The ovenbird is named for its woven, “oven-like” nest built on the ground, which is said to resemble a Dutch oven.
Owl
Owls are a nocturna order of deeply affected birds of prey found on every continent except Antarctica. They have enormous eyes, exceptional low-light vision and almost totally silent flight.
Fun Fact: It would take more owls than have ever existed to screw in a single light bulb, even if you gave them thumbs.
Owl Butterfly
Owl Butterflies are large, predominantly tropical butterflies found in the Americas. They’re named for the distinctive eye-like patterns on their wings, resembling the eyes of an owl, which make them appear a lot dumber than they are.
Fun Fact: The eye-like markings on the wings of Owl Butterflies help deter predators by creating the illusion of a much larger animal, such as an owl, potentially intimidating smaller predators.
Owlfly
Owlflies make up a family of around 450 species of neuropterans, related to lacewings. They have long, slender bodies, large eyes, and intricate wing patterns, resembling a sort of moth-like dragonfly
Fun Fact: These are highly specialized predators, capable of hunting on the wing. In fact, They are fast-flying predators of other flying insects during the day.
Ox
An ox is a domesticated bovine trained to pull heavy things for people. They’re typically castrated male cows and are used all over the world.
Fun Fact: Oxen have been used for thousands of years as working animals, and were instrumental in human success as a species when they invented agriculture.
Oxpecker
If woodpeckers peck wood, oxpeckers peck oxen. The Oxpecker is a type of bird found in sub-Saharan Africa. They’re a pretty little brown bird with a red and yellow beak
Fun Fact: These birds are so named for their symbiotic relationship with large mammals like rhinoceroses and buffalo, in which they feed on parasites and ticks found on their hosts’ bodies.
Oyster
Oysters are bivalve molluscs found in marine and brackish habitats worldwide, popular for their rich seminal flavour and ability to turn grit into shiny balls.
Fun Fact: Oysters are significant filter feeders, helping improve water quality by filtering algae and other particles from the surrounding water as they feed.
Oyster Toadfish
The Oyster Toadfish is a bottom-dwelling toadish from the North Atlantic coast, known for their unique vocalizations which they make using their swim bladders. These are reasonably ugly ambush predators who prefer to remain buried in the sand.
Fun Fact: NASA sent an oyster toadfish into space in the late ‘90s to see what would happen to their ears in microgravity. Spoiler: nothing happened to them.
Ozark Bass
The Ozark Bass is a species of freshwater fish endemic to the Ozark Highlands of Missouri and Arkansas. It’s a greenish, perch-like fish with a distinctive red eye.
Fun Fact: Ozark Bass are popular game fish in the region, and their red-ringed eyeball has earned them the nickname, “goggle-eye”.
What Other Animals Begin With ‘O’?
That completes our list of animals that begin with the letter O.
Hopefully you’ve learned a few new ones, but are there any that we’re missing in our list that you would like to see covered?
If so, get in touch. Please see our Animal A-Z list for animals that start with different letters.