Discover the complete list of 54 mammals that start with the letter “O” from all around the world. This diverse group includes everything from small rodents like the Oaxacan Big-toothed Deermouse to larger, rare species such as Owston’s Civet. Many of these mammals share unique traits and habitats, ranging from tropical rainforests and deserts to mountains and oceans. This list highlights both well-known animals and lesser-known species, providing a broad look at the fascinating variety within this alphabetical group.
Explore the detailed table below to learn more about these mammals and their scientific backgrounds.
Scientific Name This column gives the official Latin name of each mammal. It helps you identify the exact species and understand its place in scientific classification.
Habitat Here, you can see the natural homes where each mammal lives. This includes forests, grasslands, mountains, deserts, and aquatic environments.
Average Size (cm) This shows the typical length or height of each mammal in centimeters. It gives a quick idea of the animal’s size from smallest bats to large whales.
Description This section provides a brief overview of each mammal’s key features, behaviors, and role in its ecosystem. It summarizes what makes each species unique and important.
Mammals that start with O
| Mammal | Scientific Name | Habitat | Average Size (cm) |
|---|---|---|---|
| Oaxacan Big-toothed Deermouse | *Megadontomys nelsoni* | Cloud forests and humid pine-oak forests of Oaxaca, Mexico | 12.5 |
| Oaxacan Deermouse | *Peromyscus oaxacensis* | Highland forests, including pine-oak and cloud forests, in Oaxaca, Mexico | 10.0 |
| Oaxacan Pocket Gopher | *Cratogeomys tylorhinus* | Montane forests and agricultural fields in Oaxaca, Mexico | 20.0 |
| Oaxacan Spiny Pocket Mouse | *Heteromys oasacensis* | Dry forests and shrublands of Oaxaca, Mexico | 12.0 |
| Obscure Shrew | *Crocidura obscurior* | Highland forests and moist grasslands in parts of Africa | 8.0 |
| Ocelot | *Leopardus pardalis* | Tropical rainforests, scrublands, and mangrove forests from southern USA to Argentina | 75.0 |
| Ocher-bellied Funnel-eared Bat | *Natalus stramineus* | Caves and mines in Central and South America | 4.5 |
| Ochre-bellied Brush-furred Rat | *Lophuromys nudicaudus* | Tropical rainforests of Central Africa | 13.0 |
| Ochraceous Trident Bat | *Asellia tridens* | Arid and semi-arid regions across North Africa and the Middle East | 6.0 |
| Ogasawara Mole | *Mogera etigo* | Forests and grasslands of Honshu, Japan | 15.0 |
| Ogilby’s Climbing Mouse | *Dendromus nyasae* | Forests and montane grasslands in Central and East Africa | 8.0 |
| Ogilby’s Duiker | *Cephalophus ogilbyi* | Tropical rainforests of West and Central Africa | 50.0 |
| Ogilvie Mountains Collared Lemming | *Dicrostonyx richardsoni* | Arctic tundra and boreal forests of northwestern North America | 15.0 |
| Okapi | *Okapia johnstoni* | Dense rainforests of the Democratic Republic of Congo | 158.0 |
| Okinawa Horseshoe Bat | *Rhinolophus pumilus* | Forests and caves of Okinawa and Ryukyu Islands, Japan | 5.5 |
| Oldfield Mouse | *Peromyscus polionotus* | Coastal dunes and sandy fields of southeastern USA | 9.0 |
| Oldfield’s Trident Bat | *Asellia italicus* | Arid and semi-arid regions of the Middle East | 5.8 |
| Olive Colobus | *Procolobus verus* | Tropical rainforests of West Africa | 50.0 |
| Olive Grass Mouse | *Rhabdomys dilectus* | Grasslands and shrublands of Southern Africa | 11.0 |
| Olive-backed Pocket Mouse | *Perognathus fasciatus* | Grasslands and shrublands of central North America | 7.0 |
| Olive-colored Oldfield Mouse | *Peromyscus polionotus decoloratus* | Coastal dunes of Florida, USA (now extinct) | 9.0 |
| Oliver’s Pied Bat | *Chalinolobus olivieri* | Forests and open woodlands of New Guinea | 5.0 |
| Olivier’s Shrew | *Crocidura olivieri* | Diverse habitats, including grasslands and forests, across sub-Saharan Africa | 12.0 |
| Olrog’s Four-eyed Opossum | *Philander olrogi* | Tropical forests and wetlands of South America | 25.0 |
| Omura’s Whale | *Balaenoptera omurai* | Tropical and warm-temperate waters of the Indo-Pacific | 1,050.0 |
| Oncilla | *Leopardus tigrinus* | Cloud forests and montane forests of Central and South America | 45.0 |
| One-striped Grass Mouse | *Lemniscomys rosalia* | Grasslands and savannas of Southern and East Africa | 13.0 |
| One-striped Opossum | *Monodelphis unistriata* | Atlantic Forest of southeastern Brazil | 10.0 |
| Orange Nectar Bat | *Lonchophylla robusta* | Tropical rainforests of Central and South America | 6.0 |
| Orange-fingered Myotis | *Myotis rufoniger* | Forests and caves of Southeast Asia | 5.0 |
| Orange-throated Whiskered Bat | *Myotis brandtii* | Forests and woodlands across Europe and Asia | 5.0 |
| Orbiculus Leaf-nosed Bat | *Hipposideros orbiculus* | Tropical forests of Southeast Asia | 6.0 |
| Orca | *Orcinus orca* | All oceans, from Arctic to Antarctic regions | 750.0 |
| Ord’s Kangaroo Rat | *Dipodomys ordii* | Arid and semi-arid grasslands and deserts of North America | 13.0 |
| Ord’s Pipistrelle | *Pipistrellus ordii* | Forests and open woodlands of North America (historical/disputed) | 4.0 |
| Ord’s Serotine | *Eptesicus ordii* | Forests and woodlands of North America (historical/disputed) | 6.0 |
| Oribi | *Ourebia ourebi* | Grasslands and savannas across sub-Saharan Africa | 65.0 |
| Orinoco Agouti | *Dasyprocta guamara* | Tropical forests and savannas near water in Venezuela | 50.0 |
| Ornate Pipistrelle | *Pipistrellus ornatus* | Forests and urban areas of South Asia | 4.5 |
| Ornate Rock-wallaby | *Petrogale lateralis* | Rocky outcrops and cliffs in Western Australia | 55.0 |
| Ornate Shrew | *Sorex ornatus* | Forests, grasslands, and chaparral in western North America | 6.0 |
| Ornate Shrew-like Bat | *Nyctimene ornata* | Tropical forests of New Guinea and nearby islands | 10.0 |
| Ornate Tree-rat | *Mesembriomys macrurus* | Tropical savannas and woodlands of Northern Australia | 30.0 |
| Osborn’s Shrew Opossum | *Caenolestes osborni* | Cloud forests and paramo of the Andes in Colombia and Venezuela | 10.0 |
| Osgood’s Leaf-eared Mouse | *Phyllotis osgoodi* | Andean grasslands and scrublands of Peru and Bolivia | 10.0 |
| Osgood’s Mouse | *Mus osgoodi* | Forests and agricultural areas of Vietnam and Laos | 8.0 |
| Oriental Small-clawed Otter | *Aonyx cinereus* | Freshwater wetlands, rice paddies, and coastal areas of Southeast Asia | 65.0 |
| Otter-civet | *Cynogale bennettii* | Tropical rainforests and swamps of Southeast Asia | 60.0 |
| Oustalet’s Big-eared Bat | *Plecotus gaisleri* | Montane forests and caves of Morocco, Algeria, and Tunisia | 5.0 |
| Oustalet’s Red Colobus | *Piliocolobus rufomitratus* | Tropical rainforests of West Africa, particularly coastal areas | 60.0 |
| Oussou Shrew | *Crocidura douceti* | Tropical forests of West Africa | 9.0 |
| Owen’s Big-eared Bat | *Plecotus austriacus* | Grasslands, forests, and agricultural areas across Europe and Asia | 5.0 |
| Owen’s Leaf-nosed Bat | *Hipposideros oweni* | Tropical forests and caves of New Guinea | 7.0 |
| Owston’s Civet | *Chrotogale owstoni* | Tropical rainforests and evergreen forests of Southeast Asia | 70.0 |
Descriptions
Oaxacan Big-toothed Deermouse
A nocturnal rodent endemic to Oaxaca, Mexico, found in high-altitude forests. It’s known for its relatively large teeth adapted for its diet. This species is an important part of the local forest ecosystem.
Oaxacan Deermouse
A small mouse species native to the highlands of Oaxaca, Mexico. It typically inhabits forested areas, where it forages for seeds and insects. Like many deermice, it plays a role in seed dispersal.
Oaxacan Pocket Gopher
A burrowing rodent found in the mountains of Oaxaca, Mexico. It creates extensive tunnel systems, impacting soil aeration and nutrient cycling. This gopher is well-adapted for its subterranean lifestyle.
Oaxacan Spiny Pocket Mouse
A small, spiny rodent endemic to Oaxaca, Mexico, adapted to arid and semi-arid environments. Its coarse fur provides protection, and it uses cheek pouches to carry seeds, essential for its survival in dry habitats.
Obscure Shrew
A small, elusive shrew species found in specific forested and grassland regions of Africa. Shrews are known for their high metabolism and constant search for insects and other small invertebrates.
Ocelot
A medium-sized wild cat native to the Americas, recognized by its beautiful spotted coat. It is primarily nocturnal and solitary, preying on small mammals, birds, and reptiles. Ocelots are apex predators in their habitats.
Ocher-bellied Funnel-eared Bat
A small bat species found in Central and South America, known for its funnel-shaped ears. It typically roosts in caves, emerging at night to hunt insects. This bat is a key insectivore in its ecosystem.
Ochre-bellied Brush-furred Rat
A rodent native to the rainforests of Central Africa, characterized by its brush-like fur. These rats are typically ground-dwellers, playing a role in seed dispersal and the forest food web.
Ochraceous Trident Bat
A bat species found in desert and semi-desert environments, distinguished by its unique trident-shaped noseleaf. It roosts in caves or old buildings, preying on insects in arid landscapes.
Ogasawara Mole
A species of mole endemic to Honshu, Japan, typically inhabiting forests and grasslands. Moles are highly adapted for a subterranean life, digging tunnels and feeding on earthworms and other soil invertebrates.
Ogilby’s Climbing Mouse
A small arboreal mouse found in the montane forests and grasslands of East and Central Africa. It has adaptations for climbing, feeding on seeds, fruits, and insects. Its agility helps it navigate tree branches.
Ogilby’s Duiker
A small antelope species native to the rainforests of West and Central Africa. Duikers are shy, forest-dwelling ungulates that feed on fruits, leaves, and fungi. They are important seed dispersers in their habitat.
Ogilvie Mountains Collared Lemming
A lemming species inhabiting the arctic tundra and boreal forests of northwestern North America. These small rodents are known for their population cycles and seasonal fur changes, turning white in winter.
Okapi
An elusive mammal native to the Congo rainforest, often called the “forest giraffe.” It has a unique appearance with zebra-like striped legs and is related to giraffes. Okapis are solitary browsers, feeding on leaves and shoots.
Okinawa Horseshoe Bat
A small bat species endemic to the Ryukyu Islands of Japan, including Okinawa. It uses echolocation for navigation and hunting insects. These bats are crucial for insect control in their island ecosystems.
Oldfield Mouse
A small rodent native to the southeastern United States, primarily found in sandy coastal habitats. These mice are known for burrowing extensively, creating complex tunnel systems, and feeding on seeds and insects.
Oldfield’s Trident Bat
A bat species found in arid and semi-arid regions of the Middle East, characterized by its trident-shaped noseleaf. Like other trident bats, it relies on echolocation to hunt insects in dry environments.
Olive Colobus
A species of Old World monkey native to the tropical rainforests of West Africa. Known for its olive-green fur, it is arboreal and primarily herbivorous, feeding on leaves and fruits. It lives in small social groups.
Olive Grass Mouse
A widespread rodent species found in the grasslands and shrublands of Southern Africa. It’s known for the distinctive black stripes on its back. These mice are omnivorous, consuming seeds, insects, and plant material.
Olive-backed Pocket Mouse
A small pocket mouse native to the central plains of North America. It is distinguished by its olive-brown fur and cheek pouches used for carrying seeds. It’s adapted to arid environments, active at night.
Olive-colored Oldfield Mouse
An extinct subspecies of the Oldfield Mouse, once found on the coastal dunes of Florida. It was known for its distinct coloration. Its disappearance highlights the impact of habitat loss on unique mammal populations.
Oliver’s Pied Bat
A bat species native to New Guinea, found in forests and open woodlands. It has a distinctive appearance. Like most bats, it plays an important ecological role as an insectivore or pollinator.
Olivier’s Shrew
A widely distributed shrew species found across sub-Saharan Africa in various habitats. It is a voracious insectivore, consuming a high volume of prey due to its fast metabolism, contributing to insect control.
Olrog’s Four-eyed Opossum
An opossum species found in tropical forests and wetlands of South America. It is named for the distinctive light spots above its eyes, resembling a second pair of eyes. It is an omnivorous marsupial.
Omura’s Whale
A relatively newly recognized baleen whale species inhabiting tropical and warm-temperate waters. It is known for its asymmetrical coloration. These whales feed on krill and small fish, contributing to marine ecosystems.
Oncilla
A small wild cat native to Central and South America, resembling a miniature ocelot. It inhabits montane forests, primarily hunting small rodents and birds. Oncillas are solitary and nocturnal, masters of camouflage.
One-striped Grass Mouse
A rodent species found in the grasslands and savannas of Southern and East Africa, distinguished by a single dark stripe down its back. These mice are omnivorous, consuming seeds, insects, and plant material.
One-striped Opossum
A small opossum species endemic to the Atlantic Forest of southeastern Brazil. It is characterized by a single dark stripe along its back. These solitary marsupials are nocturnal, feeding on insects and small fruits.
Orange Nectar Bat
A bat species found in the tropical rainforests of Central and South America. It has a long snout and tongue adapted for feeding on nectar and pollen, making it an important pollinator for various tropical plants.
Orange-fingered Myotis
A bat species found in forests and caves across Southeast Asia. Like other Myotis bats, it is an insectivore, using echolocation to hunt. It plays a role in insect population control within its range.
Orange-throated Whiskered Bat
A bat species found across Europe and Asia, often in forested and woodland areas. It is an insectivorous bat that roosts in trees or buildings and is known for its ability to survive cold climates by hibernating.
Orbiculus Leaf-nosed Bat
A bat species native to tropical forests of Southeast Asia, characterized by its complex, circular noseleaf used in echolocation. It roosts in caves and hunts insects in dense forest environments.
Orca
The largest dolphin species, also known as a killer whale, found in all oceans. Orcas are highly intelligent apex predators, known for their complex social structures and diverse hunting strategies, preying on marine mammals and fish.
Ord’s Kangaroo Rat
A common kangaroo rat species native to the arid and semi-arid regions of North America. It is known for its hopping locomotion and large cheek pouches for carrying seeds, which it stores for later consumption.
Ord’s Pipistrelle
A potentially distinct or disputed pipistrelle bat species, often considered part of *Pipistrellus subflavus*. It would inhabit forests and woodlands, preying on small insects. Its status is often debated among mammalogists.
Ord’s Serotine
A bat species whose taxonomic status is debated, often considered a synonym or subspecies of *Eptesicus fuscus*. If distinct, it would inhabit forests and woodlands, primarily feeding on insects at night.
Oribi
A small, graceful antelope found in the grasslands and savannas of sub-Saharan Africa. Oribis are known for their distinctive large ears and tend to stay in open areas, feeding on grasses and herbs. They are quite shy.
Orinoco Agouti
A large rodent native to tropical forests and savannas of Venezuela, often near water sources. Agoutis are important seed dispersers, burying seeds and contributing to forest regeneration. They primarily eat fruits and nuts.
Ornate Pipistrelle
A small bat species found in forests and urban areas across South Asia. Like other pipistrelles, it is an insectivore, active at dusk and night. It adapts well to human-modified landscapes.
Ornate Rock-wallaby
A species of rock-wallaby endemic to rocky habitats in Western Australia. These marsupials are agile climbers, well-adapted to their rugged terrain. They are primarily nocturnal herbivores, feeding on grasses and shrubs.
Ornate Shrew
A common shrew species found in various habitats across western North America, including forests and grasslands. Shrews are tiny, high-metabolism insectivores essential for controlling insect populations.
Ornate Shrew-like Bat
A fruit bat species native to the tropical forests of New Guinea, characterized by its distinctive tubular nostrils. It feeds on fruit, playing a vital role in seed dispersal and pollination within its forest ecosystem.
Ornate Tree-rat
A large rodent native to the tropical savannas and woodlands of Northern Australia. It is arboreal, spending much of its time in trees, feeding on seeds, fruits, and insects. It’s known for its long, bushy tail.
Osborn’s Shrew Opossum
A small, elusive marsupial found in the high-altitude cloud forests and paramo of the Andes. Shrew opossums are insectivorous, contributing to the control of invertebrate populations in their unique mountain habitats.
Osgood’s Leaf-eared Mouse
A rodent species native to the Andean grasslands and scrublands of Peru and Bolivia. It is characterized by its relatively large ears. These mice are adapted to high-altitude environments, feeding on seeds and plants.
Osgood’s Mouse
A mouse species found in forests and agricultural areas of Vietnam and Laos. It is a small, widespread rodent, often living in close proximity to human settlements, feeding on various plant materials and insects.
Oriental Small-clawed Otter
The smallest otter species, found across Southeast Asia. It has distinctive partially webbed paws with reduced claws, ideal for foraging in mud. These social otters primarily eat crustaceans, mollusks, and small fish.
Otter-civet
A semi-aquatic carnivore native to the tropical rainforests and swamps of Southeast Asia. It resembles an otter with its sleek body and short legs. It mainly preys on fish, crustaceans, and small vertebrates in aquatic environments.
Oustalet’s Big-eared Bat
A species of bat found in montane forests and caves of North Africa, recognized by its exceptionally large ears. These ears aid in echolocation, allowing it to detect and capture insects in flight.
Oustalet’s Red Colobus
A striking red colobus monkey species native to the tropical rainforests of West Africa. These arboreal primates primarily feed on leaves, playing an important role in forest ecosystems. They live in social groups.
Oussou Shrew
A species of shrew found in the tropical forests of West Africa. Like other shrews, it is a small, highly active mammal with a high metabolic rate, constantly foraging for insects and other small invertebrates.
Owen’s Big-eared Bat
A wide-ranging bat species found across Europe and Asia, characterized by its large ears. It primarily hunts moths and other insects using low-intensity echolocation, often foraging close to the ground.
Owen’s Leaf-nosed Bat
A bat species native to the tropical forests and caves of New Guinea, known for its distinctive leaf-like nose structure used in echolocation. It is an insectivorous bat, playing a role in forest insect control.
Owston’s Civet
A rare and elusive civet species found in the tropical rainforests of Southeast Asia. It is nocturnal and primarily terrestrial, feeding on invertebrates and small vertebrates. Its conservation is a significant concern.