Animals

Rat snake Rat snakes are medium-to-large, mostly nonvenomous colubrid snakes found largely in the Northern Hemisphere; they prey on rodents and birds and include several popular pet species…

Ratite: flightless birds of the southern continents Ratite Ratites are a group of mostly large, flightless birds notable for a flat breastbone and Gondwanan distribution; the group includes ostriches, emu, cassowaries, rheas, kiwi and seve…

Rattlesnake Venomous New World pit vipers recognized by a segmented tail rattle; about 50 species in the genera Crotalus and Sistrurus, native from southwest Canada to central Argentina.

Raven (Corvus corax): large intelligent member of the crow family Raven An overview of the common raven (Corvus corax): appearance, behavior, cultural roles, and how it differs from crows and related corvids.

Ray (Batoidea): biology, classification, and human interactions Ray Rays (batoids) are flattened cartilaginous fishes related to sharks. This article covers their anatomy, diversity, evolution, ecology, and interactions with people, including fishe…

Razor shell (razor clam): biology, ecology and human uses Razor shell Razor shells are elongated burrowing bivalves found on sandy coasts. This article summarizes their appearance, anatomy, behavior, distribution, taxonomy, culinary uses, ecological…

Red admiral (Vanessa atalanta) Red admiral A common, strikingly patterned butterfly of temperate regions, known for strong flight, seasonal migration, and larval association with nettles.

Red deer (Cervus elaphus): description, range, behavior and human uses Red deer Comprehensive overview of the red deer (Cervus elaphus): identification, distribution, behaviour, ecology, interactions with people and conservation considerations.

Red fox (Vulpes vulpes) Red fox A widespread, adaptable fox species known for its reddish coat, bushy tail and opportunistic diet; common across the Northern Hemisphere and often living near people.

Red junglefowl (Gallus gallus) Red junglefowl A wild pheasant-like bird native to South and Southeast Asia; ancestral wild species of the domestic chicken, with distinctive plumage, behavior, and a long history of human associ…

Red kangaroo The red kangaroo (Macropus rufus) is the largest living marsupial, native to Australia’s arid interior. This article outlines its appearance, behaviour, range, reproduction, and in…

Red kite (Milvus milvus) Red kite A medium-large raptor native to Europe and northwest Africa, noted for its reddish plumage, forked tail and scavenging habits; subject of successful conservation and reintroduction…

Red panda (Ailurus fulgens): overview, traits, and conservation Red panda Small arboreal mammal of the eastern Himalayas and southwestern China, known for reddish fur, ringed tail, bamboo diet, and unique taxonomic status; faces habitat loss and conserva…

Red snapper (Lutjanus campechanus) Red snapper A medium-large marine fish of the family Lutjanidae, valued by commercial and recreational fisheries across the western Atlantic and Gulf of Mexico; notable for its red color, culi…

Red-and-green macaw (Ara chloropterus) Red-and-green macaw Large predominantly red macaw (Ara chloropterus) of northern and central South America, noted for green-and-blue wings, strong social flocks, clay-lick feeding, and threats from ha…

Red-crowned crane (Grus japonensis) Red-crowned crane A large East Asian crane species with white plumage and a red head patch, highly symbolic in culture and considered endangered due to habitat loss and small populations.

Red-eared slider (Trachemys scripta elegans) Red-eared slider A semi-aquatic freshwater turtle native to the southern United States, widely kept as a pet and introduced to many regions where it can become invasive.

Red-necked Grebe (Podiceps grisegena) Red-necked grebe Medium-large migratory waterbird of northern temperate regions, notable for its reddish-brown breeding neck, diving for fish, floating nests, and seasonal coastal migrations.

Red-necked wallaby (Macropus rufogriseus) Red-necked wallaby A medium-sized macropod native to eastern Australia and Tasmania, the red-necked wallaby is a nocturnal grazer with a grey coat and reddish neck, two subspecies, and adaptable beha…

Red-shouldered macaw (Diopsittaca nobilis) Red-shouldered macaw A compact South American macaw species notable for its green plumage, red shoulder patches and suitability as a companion bird; overview of appearance, range, behavior, breeding an…

Red-tailed Black Shark (Epalzeorhynchos bicolor) Red-tailed black shark Freshwater cyprinid from Thailand with a black body and bright red tail; popular in aquaria, largely captive-bred, and considered seriously threatened in the wild.

Red-tailed hawk (Buteo jamaicensis) — North American raptor Red-tailed hawk A widespread North American raptor known for its reddish tail, broad wings, and versatile hunting. Covers identification, range, behavior, diet, interactions with people and role i…

Red-vented bulbul (Pycnonotus cafer) Red-vented bulbul A medium-sized songbird native to tropical southern Asia; adaptable, fruit- and insect-eating, and widely introduced — often considered an invasive species with ecological and agri…

Red-whiskered Bulbul (Pycnonotus jocosus): Identification, Range, and Behavior Red-whiskered bulbul A crested passerine from tropical Asia, the red-whiskered bulbul (Pycnonotus jocosus) is a common frugivore and nectar feeder, notable for its red facial mark, lively calls, and ad…

Redbone Coonhound A medium-to-large American scent hound bred in the southern United States for tracking and treeing game; known for a deep red coat, endurance, and a melodious baying voice.

Reef triggerfish (Rhinecanthus rectangulus) Reef triggerfish A distinctive Indo‑Pacific reef fish, also called the humuhumunukunukuāpuaʻa. Noted for its locking dorsal spine, bold coloration, varied diet, territorial nesting behavior, and Ha…

Reindeer (Rangifer tarandus): biology, behavior and human relationships Reindeer Reindeer (Rangifer tarandus), called caribou in North America, are Arctic and subarctic deer known for seasonal antlers, nomadic migrations, cold adaptations and close cultural tie…

Remipedia: Blind, Cave-Dwelling Crustaceans and Their Place in Arthropod Evolution Remipedia Remipedia are small, blind crustaceans living in saline coastal aquifers and anchialine caves worldwide. They have elongated segmented bodies, distinct appendages, and a key evolut…

Remora (suckerfish): biology, behavior, and host relationships Remora Remoras are elongated marine fishes with a suction disk on the head. They attach to larger animals like sharks and turtles, feeding on scraps and parasites; relationships range fro…

Repenomamus: a large Early Cretaceous mammal from northeastern China Repenomamus Repenomamus is a genus of relatively large Early Cretaceous mammals known from fossils in northeastern China; notable for robust build, carnivorous teeth and direct evidence of fee…

Resplendent Quetzal (Pharomachrus mocinno) Resplendent quetzal A large, vividly colored bird of Central American cloud forests, the resplendent quetzal is famed for its iridescent plumage and deep cultural importance in Mesoamerica and Guatema…

Reticulated python Large non-venomous snake from Southeast Asia, often cited as the world's longest. A powerful constrictor found in diverse habitats, kept in captivity and subject to hunting, but ra…

Rhabdodontidae — Cretaceous herbivorous ornithopods Rhabdodontidae Rhabdodontidae is a family of robust, herbivorous ornithopod dinosaurs from the Cretaceous, known mainly from Europe and possibly Australia; notable genera include Rhabdodon, Zalmo…

Rhacophoridae: Old World shrub, bush and flying frogs Rhacophoridae Rhacophoridae is a family of mostly arboreal frogs from Asia and Africa, known for foam nests, adhesive toe pads and some gliding 'flying frogs'. Overview, traits, reproduction, ta…

Rhamphorhynchus: the long‑tailed Jurassic pterosaur Rhamphorhynchus Rhamphorhynchus is a well-known genus of long-tailed pterosaurs from the Late Jurassic, notable for its stiffened tail with a diamond‑shaped vane, needle-like teeth, and frequent p…

Rhea (bird) Rheas are large, flightless South American birds of the genus Rhea. Ratites adapted to open habitats, notable for long legs, three-toed feet, communal breeding by males, and import…

Rhesus macaque (Macaca mulatta) Rhesus macaque The rhesus macaque is a widespread Old World monkey of Asia, notable for adaptability, complex social organization, frequent association with people, and a long history of use in b…

Rhinatrematidae: the tailed or beaked caecilians of northern South America Rhinatrematidae Rhinatrematidae are a small family of neotropical caecilians with tails and aquatic larvae. Found in equatorial South America, they retain primitive features and occupy moist fores…

Rhinella — Neotropical true toads (beaked or Rio Viejo toads) Rhinella Rhinella is a group of Neotropical true toads—often called beaked or Rio Viejo toads—comprising roughly seventy species native to Central and South America with varied ecology and…

Rhinoceros: biology, species, distribution, and conservation Rhinoceros Rhinoceroses are large odd-toed ungulates of the family Rhinocerotidae. This article summarizes their biology, species, distribution, evolution, threats, and conservation efforts.

Rhinoceros (genus) Genus Rhinoceros comprises the two living one-horned Asian rhinoceroses: the Indian and the Javan rhino. This article covers their appearance, habitats, behavior, conservation and…

Rhinoceros hornbill (Buceros rhinoceros) Rhinoceros hornbill A large Southeast Asian hornbill with a prominent casque and powerful bill. Lives in lowland rainforests, eats mostly fruit and nuts, nests in tree cavities and is threatened by ha…

Rhodesian Ridgeback Large Southern African breed known for its distinctive backward-growing ridge of hair, used historically for hunting and guarding; dignified, athletic, and loyal with specific care…

Dicyemida (Rhombozoa) — microscopic parasites of cephalopod renal appendages Rhombozoa Dicyemida (Rhombozoa) are microscopic parasites living in cephalopod renal appendages, with simple multicellular bodies, varied life cycles, host‑specific ecology, and debated evol…

Rhynchosaur: Triassic herbivorous reptiles with distinctive beaks Rhynchosaur Rhynchosaurs were widespread Triassic diapsid reptiles known for powerful beaks, specialized teeth, and abundant fossil remains; they radiated across Pangea and disappeared by the…

Right whale (Eubalaena) — overview, traits, history and conservation Right whale Large baleen whales of the genus Eubalaena, identifiable by massive heads, unique callosities and skim-feeding; three species were heavily hunted and today face serious conservatio…

Ring‑necked snake (Diadophis punctatus): description, range, and behavior Ring-necked snake A concise overview of the ring‑necked snake, Diadophis punctatus: appearance, habits, distribution, taxonomy, defenses, diet, and conservation notes for this small North American s…

Ringed seal (Pusa hispida) Ringed seal A small earless seal of the Arctic and sub-Arctic with distinctive light-rimmed spots. Ice-dependent, prey for polar bears, and culturally important to Arctic peoples; faces threat…