6 Animals That Start with O: From Ocellated Lizards to Orcas
October 24, 2026
Animals that start with O carry some of the most interesting naming histories in zoology. “Orangutan” is Malay for “person of the forest.” “Opossum” comes from an Algonquian word that English colonists wrote down in Virginia. “Orca” borrows from Latin, and the animal itself is actually a dolphin.
This article covers six animals beginning with O: two lizards, a cephalopod, a marsupial, a great ape, and the largest member of the dolphin family. Each profile covers where the animal lives, how scientists came to describe it, and why it matters to readers in the United States. Some are backyard visitors, some are popular pets, and some live thousands of miles away but turn up in US zoos and grocery aisles.
If you are working through the alphabet, the neighboring animals that start with N make a good companion read. The table below gives a quick overview before the full profiles.
| Animal | Native Range | Typical Habitat | US Connection |
|---|---|---|---|
| Ocellated lizard | Iberian Peninsula, southern France, northwestern Italy | Rocky hills, farmland, coastal dunes | Kept by experienced reptile hobbyists |
| Ocelot gecko | Madagascar | Forest floor and leaf litter | Popular pet gecko |
| Octopus | Oceans worldwide | Reefs and rocky seafloor | Giant Pacific species off the West Coast |
| Opossum | North and Central America | Woods, farms, suburbs | Common backyard visitor |
| Orangutan | Borneo and Sumatra | Tropical rainforest canopy | Zoo residents and palm oil conservation issue |
| Orca | All oceans | Coastal and open water | Pacific Northwest pods |
1. Ocellated Lizard
The ocellated lizard (Timon lepidus) is one of the largest members of its family. Adults are usually 30 to 60 cm long, and may reach up to 90 cm (3.0 ft), with about two-thirds of that length being tail. Its green body is overlaid with black stippling, and bright blue spots (the “ocelli” that give it its name) run along the flanks.
The species has a tangled naming history. French naturalist Daudin described it in 1802, and for nearly two centuries it was filed under Lacerta lepida. The ocellated lizard Wikipedia entry lists the move to the genus Timon as a 1996 revision. Older field guides and some pet-trade listings still use the earlier name.
According to Eurolizards, its range covers extreme northwestern Italy, southern France, and most of the Iberian Peninsula. It lives in rocky mountain habitats up to 2000 meters as well as in open agricultural landscapes and coastal dunes. Portuguese speakers call it the sardão, and Spanish speakers call it the lagarto ocelado.
Important Note: Sources disagree on this lizard’s conservation status. Wikipedia lists it as Least Concern, while the Encyclopedia of Life and other sources list it as Near Threatened. Check the IUCN Red List directly for the current assessment before citing a status.
Legal protection is clearer. A care sheet from Herpeton Academy reports that, as of April 2026, the species was not found in the CITES Appendices. It is covered by the Bern Convention under its older name, which treats it as strictly protected European fauna.
For US readers, this lizard is a niche animal rather than a common pet. It needs a large, secure enclosure, so it suits advanced keepers. Anyone curious about its relatives can browse animals that start with T, which includes the tegus, another group of big, bold lizards.
2. Ocelot Gecko
The ocelot gecko (Paroedura picta) has nothing to do with the spotted wild cat. It is a small ground-dwelling gecko from Madagascar, described by Peters in 1854. As Wikipedia’s ocelot gecko page notes, it is found in leaf litter in Madagascar forests and is also a popular pet.
Many names refer to the same animal: Madagascar ground gecko, panther gecko, and pictus gecko. Spelling varies too, and you will see both Paroedura picta and Paroedura pictus in care sheets. Wild animals are brown with black markings, and some have a white stripe down the back.
The species became a fixture of the US reptile hobby because it is hardy and active. A guide from the Wisconsin herpetological community puts adults at 4.0 to 8.0 inches in snout to tail length. These geckos are mostly nocturnal to crepuscular, so floor space matters more than height. They also store fat in a thick tail, which helps them through dry spells.
Pro Tip: Keep the cool side of the enclosure at 70 to 75 degrees Fahrenheit and the basking side at 80 to 85 degrees, as the Wisconsin herps guide recommends. House males separately, because Zilla’s husbandry handbook describes them as territorial.
Wild populations live on an island thousands of miles from any US shore, yet captive-bred geckos are now widespread in American homes. For other lizards in the pet trade, the animals that start with D list covers day geckos and dragons.
3. Octopus
The octopus has fascinated writers since antiquity. Aristotle described it in his natural history, and the name comes from the Greek for “eight-footed.” The common octopus (Octopus vulgaris) was formally named by Cuvier in 1797, and the genus name later became the label for the whole group.
Its anatomy sounds like fiction. An octopus has three hearts, and its blood is blue because it carries oxygen with a copper-based protein. Most of its neurons sit in its arms, so each arm can act with a good deal of independence. These animals can squeeze through any gap larger than their beak, the only hard part of the body.
The plural of octopus causes endless arguments. All three forms below appear in print:
- Octopuses: the standard English plural and the safest choice.
- Octopi: common, but built on a mistaken Latin ending.
- Octopodes: the Greek-style plural, rare outside scientific writing.
American readers most often meet the giant Pacific octopus (Enteroctopus dofleini), which lives in the cold waters along the Pacific coast. It is a regular attraction at West Coast aquariums, where keepers give it puzzle toys and jars to open. Its lifespan is short compared with its intelligence, and most octopuses live only a few years.
Octopuses belong to the cephalopods, a group that also includes cuttlefish and squid. You can find more of these sea animals in the animals that start with S list.
4. Opossum
The Virginia opossum (Didelphis virginiana) is the only marsupial native to North America north of Mexico. Its ancestors moved north from South America over millions of years, long before people arrived. The name entered English in the early 1600s, when colonists in Virginia recorded a word from the Powhatan language, part of the Algonquian family.
That origin explains the odd spelling. The leading “o” is often dropped in speech, which is why Americans say “possum.” Australia’s possums, though, are a separate group of marsupials that only share the nickname. The animals that start with P page covers them under the P spelling.
Opossums are slow, shy, and easy to misjudge. When badly frightened, an opossum may fall into an involuntary state that looks like death, which gave us the phrase “playing possum.” This is a nervous-system reaction rather than a performance.
Young opossums are born tiny and climb into the mother’s pouch to nurse. Later they ride on her back. Adults eat insects, snails, fruit, and carrion, so they act as informal cleanup crews in backyards, farms, and city alleys across most of the country.
5. Orangutan
The word orangutan comes from the Malay “orang hutan,” meaning “person of the forest.” There are three living species: the Bornean orangutan (Pongo pygmaeus), the Sumatran orangutan (Pongo abelii), and the Tapanuli orangutan (Pongo tapanuliensis). Scientists described the Tapanuli species only in 2017, which made it the first new great ape species named in nearly a century.
Orangutans are the largest tree-dwelling mammals on Earth. Their arms are much longer than their legs, and they move through the canopy with slow, deliberate climbs. Each night they weave a fresh sleeping nest from branches and leaves. Adult males develop wide cheek pads called flanges.
Orangutans raise their young more slowly than almost any other mammal. A mother nurses and teaches her offspring for years, so a population cannot bounce back quickly after losses. The IUCN lists all three species as Critically Endangered, and forest clearing for palm oil plantations is a major driver.
Pro Tip: American shoppers can check packaged foods and soaps for Roundtable on Sustainable Palm Oil (RSPO) certification on the label. Buying certified products is one practical way to reduce demand for palm oil from cleared rainforest.
Most Americans meet orangutans at accredited zoos, where they are known for tool use and problem solving. Those programs also support field conservation in Borneo and Sumatra.
6. Orca
The orca (Orcinus orca) is the largest dolphin, and the scientific name comes from Linnaeus in 1758. “Orca” likely traces to the Latin orcus, a term linked to the underworld. The older name, killer whale, is thought to be a reversal of sailors’ phrase “whale killer,” which described its habit of hunting other whales.
Orcas live in every ocean, and their behavior varies by population. Scientists divide them into ecotypes. Resident pods eat fish, transient pods hunt marine mammals such as seals, and offshore groups roam farther out to sea. Pods are family units led by older females, and they pass hunting methods and calls down through generations. Whale lovers can find related giants in the animals that start with W list.
The best-known US population is the Southern Resident group, which lives in the waters of Washington State and British Columbia. These orcas depend heavily on Chinook salmon, and the group was listed under the US Endangered Species Act in 2005. Boat noise and shrinking salmon runs are common concerns, and whale-watching boats in the San Juan Islands now follow distance guidelines.
Orcas also shaped American views of captivity. Captures in Puget Sound and British Columbia during the 1960s led to the first marine park shows. Public attitudes shifted over the following decades, and SeaWorld announced in 2016 that it would end orca breeding.
From a Spanish hillside lizard to a salmon-hunting dolphin off Seattle, these six animals that start with O show how much variety one letter can hold. Each came to science and to popular culture by a different route, and several of them still need protection.