Animals

Riodinidae (metalmarks): an overview of the butterfly family Riodinidae Riodinidae, commonly called metalmarks, are a diverse family of mostly Neotropical butterflies noted for metallic wing markings, ant associations in larvae, complex taxonomy, and a…

Riojasaurus Riojasaurus, a robust early sauropodomorph from Late Triassic Argentina, is known from multiple skeletons and sheds light on the origin of large, quadrupedal plant-eating dinosaurs…

Risso's dolphin (Grampus griseus) Risso's dolphin A widely distributed oceanic dolphin, distinctive for its blunt head and extensive white scarring; the only living species in the genus Grampus and a specialist predator of squid.

River dolphin A group of dolphins adapted to freshwater and near‑shore habitats. River dolphins are known for long beaks, flexible necks, limited eyesight and high vulnerability from habitat los…

Roach's mouse-tailed dormouse (Myomimus roachi) Roach's mouse-tailed dormouse A small, uncommon dormouse of the Gliridae family found in parts of Bulgaria, Greece and Turkey; terrestrial tendencies, nocturnal habits, and conservation concerns from habitat lo…

Roadrunner (Geococcyx): the fast-running ground cuckoo Roadrunner A compact overview of roadrunners (genus Geococcyx): appearance, behavior, habitat, diet, reproduction, and cultural notes about this distinctive North American bird.

Roar (animal vocalization) Roar (utterance) A roar is a loud, low-pitched vocalization produced by a variety of animals. This article explains how roars are made, their purposes, the species that perform them, and how roars…

Roaring Lion (Thoroughbred racehorse) Roaring Lion (horse) American-bred, British-trained Thoroughbred racehorse (2015–2019). Champion two-year-old in Britain and a leading middle-distance winner in 2018, later retired to stud and died aft…

Roborovski hamster (Phodopus roborovskii) — overview and care Roborovski hamster Smallest commonly kept pet hamster from the Gobi region. Fast, social, and burrowing; requires escape-proof housing, appropriate diet, and observation-focused care rather than freq…

Rock dormouse (Graphiurus platyops) Rock dormouse A small nocturnal rodent of southern Africa, the rock dormouse (Graphiurus platyops) is a member of the Gliridae family adapted to rocky habitats and crevices across several countr…

Rock pigeon (Columba livia): overview, behavior, and relationship with people Rock pigeon The rock pigeon (Columba livia), often called the rock dove or common pigeon, is a widespread bird of the family Columbidae found in wild, domestic and feral forms across cities an…

Rock ptarmigan (Lagopus muta): Arctic and alpine grouse Rock ptarmigan A compact overview of the rock ptarmigan (Lagopus muta): identification, seasonal plumage, habitat, behavior, cultural importance and conservation across Arctic and mountain region…

Rockhopper penguin A small, crested penguin of the genus Eudyptes known for hopping among rocky shore colonies; includes northern, eastern and western forms and faces population declines from human a…

Rodents (Order Rodentia): Characteristics, Diversity, and Human Interactions Rodent Rodents are the largest order of mammals, defined by continuously growing incisors. This article outlines their anatomy, diversity, evolution, roles in ecosystems, relationships wi…

Roe deer (Capreolus capreolus): the European roe deer Roe deer Small, widespread deer of temperate Europe and Asia Minor. Overview of appearance, behaviour, reproduction, habitat, human interactions and differences from the Siberian roe deer.

Rose-ringed parakeet (Psittacula krameri) — description, distribution and behaviour Rose-ringed parakeet A widespread green parakeet native to Africa and South Asia, notable for the male's neck ring, long tail, vocal nature, adaptability to urban areas, and growing feral populations w…

Rotifers (Phylum Rotifera): microscopic aquatic animals Rotifer Rotifers are microscopic, mainly freshwater animals of the phylum Rotifera. They have a ciliated corona and a mastax, show diverse lifestyles, often reproduce by parthenogenesis, a…

Rottweiler Robust German working breed noted for a black-and-tan coat, strength, and versatility as a guardian, herding helper, and family companion.

Rough‑skinned newt (Taricha granulosa) Rough-skinned newt A Pacific Northwest amphibian noted for its potent tetrodotoxin defense, amphibious life cycle, and ecological role in predator–prey coevolution.

Rough-toothed Dolphin (Steno bredanensis): Oceanic Dolphin of Tropical Deep Waters Rough-toothed dolphin Overview of the rough-toothed dolphin (Steno bredanensis), a slim, medium-large oceanic species of tropical deep waters worldwide, detailing its appearance, behavior, diet, distrib…

Rove beetle (Staphylinidae) Rove beetle Rove beetles (family Staphylinidae) are a vast, ancient group of beetles recognized by short elytra and exposed, flexible abdomens. They occupy diverse habitats and play important…

Royal ghost frog (Heleophryne regis) Royal ghost frog A South African ghost frog (Heleophryne regis) occupying cool forest and mountain stream habitats; adapted to fast-flowing water and facing threats from habitat loss and water dist…

Rufous hare-wallaby (mala): appearance, range, and conservation Rufous hare-wallaby The rufous hare-wallaby (mala) is a small, nocturnal Australian macropod once widespread across western Australia; now confined to offshore islands and targeted by active recovery…

Rugops — a small abelisaurid theropod of the mid‑Cretaceous Rugops Rugops was a modestly sized abelisaurid theropod from mid‑Cretaceous Africa, noted for a wrinkled snout and debated feeding habits; it lived alongside much larger predators and is…

Ruminant: cud‑chewing herbivores with specialized stomachs Ruminant Herbivorous ungulates that ferment cellulose in a multi‑chambered stomach and regurgitate cud for rechewing; ecologically and agriculturally important (cattle, deer, goats, etc.).

Ruminantia — the ruminant mammals Ruminantia Ruminantia is the suborder of even-toed ungulates characterized by specialized multi-chambered stomachs and rumination; includes cattle, deer, giraffes, antelopes, sheep and goats.

Rüppell's fox (Vulpes rueppelli) — desert fox of North Africa and the Middle East Rüppell's fox A small desert fox native to North Africa, the Arabian Peninsula and parts of South Asia. Known as the sand fox, it is adapted to arid landscapes and is named after the naturalist…

Rusty-spotted cat (Prionailurus rubiginosus) Rusty-spotted cat A compact article on the rusty-spotted cat, one of the world's smallest wild felids: appearance, behavior, range in South Asia, threats, and conservation status.

Rutiodon — a Late Triassic phytosaur Rutiodon Rutiodon was a crocodile-like phytosaur of the Late Triassic in eastern North America; semi-aquatic ambush predator with nostrils set high on the skull and convergent features with…

Saber-toothed cat: anatomy, evolution, and paleobiology Saber–toothed cat Extinct carnivorous mammals with enlarged upper canines that evolved repeatedly. Overview of anatomy, taxonomy, hunting hypotheses, fossil record, diversity, extinction theories an…

Sable (Martes zibellina): forest marten and source of prized fur Sable The sable (Martes zibellina) is a medium-sized marten native to northern Asia. Known for its dense, lustrous fur, it inhabits boreal and mixed forests and figures in ecology, histo…

Sacred kingfisher (Todiramphus sanctus) — description, habitat and behaviour Sacred kingfisher A medium-sized turquoise kingfisher of Australasia. Covers identification, distribution, diet, breeding, vocalisations, cultural significance in New Zealand and conservation notes.

Saddleback toad (Brachycephalus) — tiny cloud-forest frogs Saddleback toad Small, often brightly colored frogs of the genus Brachycephalus, endemic to montane Atlantic Forests of southeastern Brazil; notable for miniature size, digit reduction and direct…

Saffron cod (Eleginus gracilis): description, habitat and use Saffron cod Saffron cod (Eleginus gracilis) is a small North Pacific gadid found in coastal, brackish and freshwater habitats; fished regionally for food, especially in Russian waters, and eco…

Saint Helena plover (Wirebird) Saint Helena plover A small plover endemic to Saint Helena, the wirebird is a ground‑nesting shorebird of cultural and conservation importance, known for its delicate legs, restricted range, and threa…

Saint Vincent amazon (Amazona guildingii) Saint Vincent amazon A colorful parrot species endemic to Saint Vincent in the Caribbean, the Saint Vincent amazon is a canopy-dwelling parrot of conservation concern noted for its vivid head coloratio…

Salamander (order Caudata/Urodela) Salamander Overview of salamanders (order Caudata/Urodela): biology, life cycle, diversity, ecology, regeneration, and conservation issues affecting these tailed amphibians.

Salamandridae — true salamanders and newts Salamandridae Salamandridae is a family of amphibians that includes true salamanders and newts. This article summarizes their appearance, life cycles, distribution, notable genera, ecological ro…

Salamandroidea (advanced salamanders): overview and significance Salamandroidea Salamandroidea is the suborder of 'advanced' salamanders, united by internal fertilization, diverse life histories, and a near-global distribution. This entry summarizes their trai…

Salmon (Salmonidae): biology, life cycle, uses and conservation Salmon Salmon are ray‑finned fish of the family Salmonidae, noted for anadromous migrations, culinary value and cultural importance. This article summarizes their biology, life cycle, hum…

Salmonidae — family of salmon, trout, chars, graylings and whitefishes Salmonidae Salmonidae are cold-water, ray-finned fishes including salmon, trout, chars, graylings and whitefishes; noted for anadromy in many species, an adipose fin, ecological importance an…

Salp — a barrel-shaped, free-swimming tunicate of the open ocean Salp Salps are gelatinous, barrel-shaped tunicates that swim by jet propulsion, filter microscopic plankton, form large blooms (notably in the Southern Ocean), and influence ocean carbo…

Saltasaurus — armored titanosaur of the Late Cretaceous Saltasaurus Saltasaurus was a Late Cretaceous titanosaur from Argentina, notable as the first sauropod discovered with bony skin plates (osteoderms); its fossils changed ideas about sauropod a…

Saltopus — small Late Triassic reptile (Saltopus elginensis) Saltopus Saltopus was a tiny, lightly built Late Triassic reptile known from a single fragmentary skeleton found in Scotland. Its exact relationships are uncertain; it offers clues to early…

Saltwater crocodile (Crocodylus porosus) Saltwater crocodile An encyclopedic overview of the saltwater crocodile (Crocodylus porosus): appearance, distribution, behavior, evolution, human interactions, conservation, and distinguishing featur…

Samoyed (dog): Origin, Characteristics, Temperament and Care Samoyed (dog) The Samoyed is a northern working dog known for its thick white coat, curled tail and friendly 'smile'. Bred by Siberian herders for sled and herding work, it remains a popular com…

Sand cat (Felis margarita) Sand cat Small desert-dwelling wildcat adapted to arid regions of Africa and Asia. Notable for sandy coat, furry footpads, nocturnal hunting, independence, and specialized desert survival a…

Sand dollar: flattened burrowing echinoids and their ecology Sand dollar Sand dollars are flattened, burrowing sea urchins (order Clypeasteroida) with a rigid test and petaloid pore system. This article covers their form, habitat, ecology, fossil record…