30 Animals That Start With “O”

There are thousands of animals in the world, and we all know the most common ones that start with the letter O such as octopus and orangutan, but what are less commonly known animals? Here is a list of the most unique animals that begin with “O” including pictures and more! 

1. Oak Toad

The oak toad is the smallest in North America; it only reaches up to 33 millimeters! This toad species is on the verge of extinction and is highly threatened by habitat loss.  

Learn More: Virginia Herpetological Society

2. Oarfish

The oarfish is a giant fish that is the world’s largest bony fish. It can grow up to 5.5 kg and weigh a whopping 272 kilograms! Although they are extremely large, they are not dangerous and are often eaten if caught. They are also known to predict earthquakes, demonstrating their predictions by washing up on the shore. 

Learn More: National Geographic

3. Ocelot

The ocelot looks very similar to other big cats, such as the cheetah and leopard. However, it has many differences. The ocelot is found in the United States, Mexico, as well as Central and South America. This nocturnal mammal is also known as the painted leopard but is generally very small- just a bit bigger than the average house cat. 

Learn More: National Geographic

4. Octopus

Octopi have eight tentacles and are extremely intelligent! They have three hearts, but their tentacles have a mind of their own. If you cut off an arm, it will react even though it is not connected to the rest of the body. They also have blue blood and are incredibly flexible and can maneuver through tiny spaces. They also make for a great snack! 

Learn More: Smithsonian Magazine

5. Oilbird

Oilbirds are native to South America. They are nocturnal and feed off of various fruits and nuts. They are similar to bats in that they use echolocation to navigate through the night and find their way back to their nests. Their chirps are also unable to be heard by humans! 

Learn More: Britannica

6. Okapi

Okapi lives in the rainforests of Congo. These endangered animals are on the verge of being extinct due to habitat loss and human environmental impacts. They are the only relative of a giraffe but are considered to look like a mix of deer and zebras. 

Learn More: National Geographic

7. Olive Ridley Sea Turtle

The Oliver Ridley sea turtle is an endangered species that is being rehabilitated and protected by the Endangered Species Act. Their shell has an olive green hue, and they lay their eggs in deep holes in the sand of beaches. Mother sea turtles never see their babies, as they leave once they lay their eggs in the sand and the babies navigate their way to the ocean once hatched.

Learn More: NWF

8. Olm

Olms are amphibians that are classified as salamanders. They are most often found in caves across Europe, but are entirely aquatic and spend most of their time underwater or underground. Olms lack the sense of sight and navigate their surroundings through the use of ultrasonic hearing, smell, and electrosensitivity. 

Learn More: Britannica

9. Onager

The onager is a herbivore native to Iran and other parts of Asia. They are also known as the Persian Zebra. They look similar to donkeys but are distinguishable by their sandy coat and brown dorsal stripe. They are often found in mountain steppes or desert-like areas around Saudi Arabia but can be found in places far North, such as Russia, or far East, like Mongolia.  

Learn More: Smithsonian National Zoo

10. Opaleye Fish

Opaleye fish are similar to many other fish, but their distinct eyes classify them. Their eyes are big and have a blue-green color, but the rest of their body has a dark olive-green coloring. They are often found in shallow, rocky areas and are caught by local fishermen to be cooked and eaten! 

Learn More: Pier Fishing

11. Openbill Stork

The open-bill stork has glossy black wings and a tail that appears to be purple or green. They can only grow to be around 83 cm tall and are coming close to becoming endangered as their population decreases. They live in wetland habitats and are often found in flood fields in Asia. 

Learn More: Animalia

12. Opossum

Opossums are omnivores that eat many different plants and animals; most of the time feeding on dead animals and plants. They are great for farmers as they kill tills and are the only marsupial in North America! Opossums play dead when they are scared and only live up to 2 years. 

Learn More: National Geographic

13. Orangutan

Orangutans are a type of ape that sleep and live in large trees. These mammals climb up high and build nests; making them the only mammals that live off of the ground! They have extremely large arms and often eat with their feet! They can be found in tropical rainforests, but are facing a crisis of deforestation- putting them on the endangered species list. 

Learn More: World Wildlife Organization

13. Orb Weaver

The orb weaver is a nocturnal arachnid that lives in warmer parts of the world. They can be identified by their bright color, large abdomen, and incredibly large webs that can reach up to 1 meter wide. These spiders are not aggressive so there is no need to be afraid of a spider bite if you spot one.  

Learn More: Wildlife Heritage

15. Orca

Orcas look like a type of whale, but they are actually part of the dolphin family. Another common name for the orca is the killer whale. They are extremely intelligent and can live to be 80 years old. These dolphins are the world’s strongest predators and can be recognized by their black bodies and white eyes. They hunt animals such as seals, penguins, squid, and other marine animals.  

Learn More: National Geographic

16. Oribi

Oribis are found in Africa. They have many predators, including eagles, wild dogs, hyenas, and lions. These herbivores are threatened by habitat destruction due to human populations and expansion. 

Learn More: Britannica

17. Oriental Cuckoo

The Oriental Cuckoo can be found in the Himalayan mountains throughout China, Korea, and Japan. They also are native to New Zealand.  Their shape resembles a falcon, but they are quite small. They have smooth wings and a long dark grey tail. 

Learn More: NZ Birds Online

18. Oriole

Orioles are beautifully bright orange birds common to North America. They migrate in the Winter to survive and are quite easy to identify in your backyard or the open woodlands. They are attracted to feeders with nectar and fruits. 

Learn More: EBird

19. Ornate Chorus Frog

Ornate chorus frogs are relatively small frogs with extremely colorful coats. They can be gray, green, and reddish brown, which a black stripe across their eyes. These frogs are found across wetlands in North America, such as the South Carolina Coastal Plain. These amphibians breed in shallow bodies of water and live near open grassy areas with water. 

Learn More: Savannah River Ecology Laboratory

20. Oryx

The oryx is an antelope found only in Africa and the Middle East. They have long horns and grey bodies that make them easy to identify. However, these hooved mammals are severely endangered and only live in their native habitat. 

Learn More: African Wildlife Foundation

21. Osprey

The Osprey is often known as a sea hawk because they feed off of fish. Ospreys live on every continent with the exception of Antarctica. They have a wingspan that can reach up to 6 feet, and they grow to be around 23 inches long. 

Learn More: Scottish Wildlife Trust

22. Ostracod

Ostracods are marine animals that produce bioluminescence. They are one of the oldest species in the world, even older than oysters in which they have been found in history for over 500 million years. Ostracods are omnivores, but most often eat algae and dead plants or animals. 

Learn More: Lake Biwa Museum

23. Ostrich

Ostriches are giant birds that can run, but can’t fly! They are the fasted birds in the world that can run up to 43 mph. They are found in the savannas of Africa and in many zoos across the world. They eat mostly plants but sometimes crave small insects and reptiles. 

Learn More: Smithsonian National Zoo

24. Otter

Otters are marine animals that lack a layer of blubber. They have thousands of water-resistant hair follicles that keep them warm while they are in the water. There are over 13 species of otter in the world, including the giant otter and the giant river otter.  90% of them live in Alaska! 

Learn More: U.S. Department of the Interior

25. Outstalet’s Chameleon

Chameleons are interesting animals as they can change their color to camouflage their surroundings or even show their mood! The outstalet’s chameleon is the world’s largest chameleon and can grow up to 2 feet in length. They are native to Madagascar but can be found in various other parts of the world. 

Learn More: Reptiles Magazine

26. Oxen

Oxen are also known as male bulls. They have been domesticated and are used as mules for farm work. They are extremely strong animals and have large horns. You can find oxen in all countries except for South America and Australia. 

Learn More: Britannica

27. Oxford Sheep

Oxford sheep are often killed and used for creating fleece. The rams weigh around 300 pounds, and their ewes average about 200 pounds. They are native to the United Kindom in Oxford Country and can be found among farms and grasslands.

Learn More: The Livestock Conservancy

28. Oxpecker

Oxpeckers do exactly what their name says; they peck the bugs and parasites off of oxen, zebra, and other mammals. They can be identified by their big,  round yellow eyes and bright red beak. They are most commonly found in Africa in the savannah or grasslands where larger mammals are found. 

Learn More: Hluhluwe

29. Oyster

Oysters are one of the oldest animals on the planet. They have been around for over 14 million years! They have gills similar to fish, but instead of using them for breathing, they use them for eating algae and plants! They are also able to change their sex depending on their environment; meaning one could start as a male and transition into a female!

Learn More: A-Z Animals

30. Oyster Catcher

Oystercatchers live near the ocean and are black and white wading birds with long orange bills. They only eat shellfish–especially oysters! They are found in temperate and tropical parts of the world and prefer to walk rather than fly.  

Learn More: Britannica