76 terms defined

Wildlife & Conservation Glossary

Plain-English definitions of the terms used across our wildlife guides, appeals and rescue guides.

By the WARN Research & Conservation Team · Last updated July 2026

In brief

This glossary defines 76 terms used across WARN's wildlife guides, appeals and rescue guides — from IUCN Red List categories and CITES appendices to CNVR, aposematism, mast fruiting and the Five Domains welfare model. Each definition stands on its own, in plain English.

Conservation status

CITES — also Convention on International Trade in Endangered Species: The Convention on International Trade in Endangered Species of Wild Fauna and Flora, an international agreement regulating cross-border trade in wild species. Species are listed in one of three appendices according to how much trade threatens them, and permits are required to move listed specimens between countries.
CITES Appendix I: The strictest CITES listing, covering species threatened with extinction where commercial international trade is generally prohibited. Trade is permitted only in exceptional circumstances, such as scientific research, and requires both export and import permits.
CITES Appendix II: A CITES listing for species not necessarily threatened now but which may become so unless trade is controlled. International commercial trade is allowed with an export permit confirming the specimen was legally obtained and that trade will not harm the wild population.
Critically Endangered — also CR: The highest IUCN threat category short of extinction, applied to species facing an extremely high risk of extinction in the wild. A species qualifies by meeting thresholds for severe population reduction, a very small or rapidly shrinking range, or an extremely small population. Critically endangered animals
Data Deficient — also DD: An IUCN category meaning there is not enough information to assess a species' extinction risk. It is not a statement that the species is safe — many Data Deficient species turn out to be threatened once surveyed.
Endangered — also EN: The IUCN category for species facing a very high risk of extinction in the wild — one step below Critically Endangered and one above Vulnerable. In everyday speech "endangered" is often used loosely for any threatened species, but on the Red List it is a specific category with defined thresholds. Endangered animals
Endemic: Found naturally in one place and nowhere else. Endemism raises extinction risk sharply, because a single event in a single location can affect the entire global population — the okapi, for example, occurs only in the Democratic Republic of the Congo.
Extinct in the Wild — also EW: An IUCN category for species that survive only in captivity, cultivation or as a reintroduced population outside their historic range. Recovery depends on breeding programmes and, eventually, habitat secure enough to release into. Extinct in the Wild
IUCN Red List — also Red List: The IUCN Red List of Threatened Species is the global inventory of the conservation status of animals, fungi and plants. Each assessment places a species in a category from Least Concern to Extinct, based on quantitative criteria covering population size, rate of decline and geographic range, and records the year the assessment was made. Sourcing & editorial standards
Least Concern — also LC: The IUCN category for widespread and abundant species that do not qualify for any threatened category. A Least Concern listing describes the species globally and can conceal severe regional declines — barn owls are Least Concern worldwide while falling sharply across intensively farmed landscapes.
Near Threatened — also NT: An IUCN category for species that do not currently qualify as threatened but are close to the thresholds, or would qualify without ongoing conservation work. It functions as an early warning rather than a clean bill of health.
Population trend: The direction a species' population is moving — increasing, stable, decreasing or unknown — recorded alongside its IUCN category. Trend often matters more than the category itself: a Least Concern species in steep decline may need attention sooner than a stable Vulnerable one.
Vulnerable — also VU: The least severe of the three IUCN threatened categories, applied to species facing a high risk of extinction in the wild. A Vulnerable species is genuinely threatened, but at lower assessed risk than an Endangered or Critically Endangered one. Vulnerable animals

Threats

Bioaccumulation: The build-up of a persistent substance in an animal's body faster than it can be excreted, concentrating further at each step up the food chain. DDT bioaccumulating in fish-eating birds thinned their eggshells and nearly wiped out the bald eagle before the chemical was banned.
Bushmeat: Meat from wild animals hunted for food, particularly in tropical forest regions. Subsistence hunting has long been sustainable at low intensity; commercial bushmeat supply to towns and to logging and mining camps is not, and can empty a forest of large animals while leaving the trees standing.
Bycatch: Animals caught unintentionally during fishing operations, including dolphins, turtles, sharks and seabirds. Bycatch is the leading cause of death for several marine species and is addressed through gear modification, exclusion devices and closed areas rather than by reducing fishing alone.
Habitat fragmentation: The breaking of continuous habitat into isolated patches by roads, farmland, settlements or other development. Fragmentation can be more damaging than outright habitat loss, because small isolated populations cannot interbreed, lose genetic diversity and cannot recolonise after a local die-off.
Human-wildlife conflict: Situations where wild animals damage crops, livestock or property, or threaten human safety, and people retaliate. It is a leading cause of large-carnivore and elephant deaths worldwide, and is addressed by protecting livestock, compensating losses and separating animals from settlements rather than by removing the animals.
Poaching: Illegal killing or capture of wild animals, whether for meat, body parts, trophies or the live-animal trade. Poaching is distinguished from legal hunting by breaching the law of the country concerned, not by the method used.
Retaliatory killing: Killing a wild animal in response to real or suspected damage to livestock, crops or people. It differs from poaching in motive rather than legality, and it responds to practical mitigation — predator-proof enclosures, rapid compensation and community engagement — far better than to enforcement alone.
Secondary poisoning: Poisoning that occurs when a predator or scavenger eats an animal that has itself been poisoned. Second-generation rodenticides are the classic case: a poisoned rat stays active and easy to catch for days, so it is exactly the prey an owl, fox or hawk is most likely to take.
Snare: A wire or cable noose set to catch an animal by the leg, neck or body. Snares are cheap, silent and entirely indiscriminate — they catch whatever walks into them — and cause severe injury or slow death. Removing them from protected areas is a core anti-poaching activity.
Wildlife trafficking — also Illegal wildlife trade: The illegal trade in wild animals, their parts and derivatives across borders and within countries. It operates as organised crime, spanning live pets, traditional medicine ingredients, meat, skins, ivory and souvenirs, and is one of the largest illegal trades in the world. Animals threatened by wildlife trafficking

Rescue & welfare

CNVR — also Catch-Neuter-Vaccinate-Release, Catch-Neuter-Vaccinate-Return: Catch-Neuter-Vaccinate-Release: the World Health Organization-endorsed method for managing free-roaming dog populations humanely. Dogs are caught, sterilised, vaccinated against rabies, marked, and returned to their own territory. Over time it stabilises then reduces the population and breaks rabies transmission, which culling does not. Karachi street dogs appeal
Confiscation: Seizure of illegally traded or kept wild animals by authorities. Confiscation creates an immediate welfare problem as well as solving one: seized animals need veterinary care, quarantine and often lifelong housing, which is why confiscation-to-sanctuary capacity is a limiting factor in enforcement.
Enrichment: Changes to a captive animal's environment that let it perform natural behaviours — foraging puzzles, climbing structures, scent trails, novel objects. Enrichment is a welfare requirement rather than a luxury: animals without it commonly develop stereotypic behaviour.
Five Domains model: A framework for assessing animal welfare across nutrition, physical environment, health, behavioural interactions and resulting mental state. It succeeded the older Five Freedoms by shifting the question from avoiding harm to assessing what the animal actually experiences.
Quarantine: Isolating a newly arrived or sick animal from others for a set period, to prevent disease spreading through a rescue centre or sanctuary. It is standard practice for confiscated animals, whose health history is unknown.
Rehabilitation: Veterinary and behavioural care given to a wild animal with the specific goal of returning it to the wild. Successful rehabilitation requires the animal to regain the physical condition and the natural behaviour it needs to survive, which is why prolonged human contact can disqualify an animal from release.
Sanctuary: A facility providing permanent care for animals that cannot be returned to the wild, with no breeding, no commercial trade in animals and no direct public contact with them. The word is unregulated in most countries, so a facility calling itself a sanctuary may not meet any of those standards.
Sentience: The capacity to have subjective experiences, including pain, distress and pleasure. Evidence of sentience underpins animal welfare law; in several jurisdictions the evidence for cephalopods and decapod crustaceans was strong enough to extend legal protection to them.
Soft release: Releasing a rehabilitated or captive-bred animal gradually, with a period of acclimatisation in an enclosure at the release site and continued food support afterwards. It contrasts with hard release, where the animal is freed directly, and generally produces better survival for species that must learn a territory.
Stereotypic behaviour — also Stereotypy: Repetitive, invariant behaviour with no apparent purpose — pacing a fixed route, head-weaving, over-grooming, bar-biting. It is a recognised indicator of poor welfare in captive animals, usually linked to an environment that prevents normal behaviour.
Symbolic adoption: A donation scheme in which a supporter funds care for a species or programme and receives a certificate and updates. No animal is owned, transferred or reserved for the donor, and no animal is taken home. Adopt an animal
TNR / TNVR — also Trap-Neuter-Return, Trap-Neuter-Vaccinate-Return: The equivalent of CNVR applied to community and feral cats: cats are trapped, sterilised, vaccinated, ear-tipped for identification and returned to their colony. Ear-tipping allows a returned cat to be recognised at a distance so it is not trapped repeatedly.
Translocation: Deliberately moving wild animals from one location to another, whether to re-establish a population, relieve human-wildlife conflict or escape an immediate threat. Translocation frequently fails when the original cause of the problem remains — a moved animal often returns or is replaced by another.

Animal biology

Aestivation: Dormancy through hot or dry conditions, the summer counterpart to hibernation. Land snails aestivate behind a sealed membrane called an epiphragm, and some desert species can remain in that state for months.
Altricial: Born or hatched helpless — blind, largely immobile and dependent on parental care. Altricial young contrast with precocial young, which are mobile and relatively self-sufficient almost immediately, as ducklings and foals are.
Apex predator: A predator with no natural predators of its own as an adult, sitting at the top of its food chain. Apex predators regulate the numbers and behaviour of species below them, so their loss can cascade through an ecosystem.
Aposematism — also Warning colouration: Conspicuous colouring or markings that advertise an animal is toxic, venomous or foul-tasting. Ladybirds, monarch butterflies and poison dart frogs are all aposematic: being noticed is the point, because a predator that samples one learns to avoid the pattern.
Arboreal: Living mainly in trees. Arboreal animals typically show adaptations such as grasping hands and feet, a prehensile tail, or the ability to rotate the ankles for head-first descent, as kinkajous do.
Binomial nomenclature — also Scientific name: The two-part naming system giving every species a genus and species name, written in italics — Panthera leo for the lion. It provides one unambiguous name worldwide, unlike common names, which vary by language and region and are frequently reused for unrelated animals.
Convergent evolution: Unrelated lineages independently evolving similar solutions to the same problem. Giant pandas and red pandas both evolved a false thumb from a wrist bone for gripping bamboo despite being only distantly related, and puffins resemble penguins for the same reason: both pursue fish underwater.
Countershading: Camouflage in which an animal is dark above and pale below, so it blends with deep water or ground when seen from above and with bright sky or surface light when seen from below. Penguins, sharks and many fish are countershaded.
Crepuscular: Active mainly at dawn and dusk, rather than through the night (nocturnal) or the day (diurnal). Many prey species are crepuscular because low light offers cover while avoiding the peak activity of both day- and night-hunting predators.
Echolocation: Locating objects by emitting sound and interpreting the returning echoes. Bats, toothed whales and dolphins, and some birds use it to navigate and hunt in darkness or turbid water where vision is useless.
Gestation: The period between conception and birth in a live-bearing animal. Gestation length varies enormously and is not simply a function of size — an elephant carries a calf for around 22 months, a scorpion can gestate for over a year.
Invasive species: A species introduced outside its natural range that spreads and causes ecological or economic harm. Not every introduced species becomes invasive, but those that do are a leading cause of extinction on islands — introduced rats, cats and stoats drove the kākāpō from mainland New Zealand.
Irruption: An irregular, large-scale movement of animals far outside their normal range, driven by food supply or population size rather than by a regular migration route. Snowy owl irruptions south into North America often follow a *good* breeding season, not a failed one.
Keystone species: A species whose effect on its ecosystem is disproportionately large relative to its abundance. Removing one restructures the whole community — sea otters keep sea urchin numbers down, and without them urchins can strip kelp forests entirely.
Lek: A mating system in which males gather to display competitively in a shared area while females visit, assess them and choose, then raise young alone. Kākāpō males boom from excavated bowls at a lek — the only parrot in the world that does so.
Mast fruiting — also Masting: Synchronised heavy fruiting or seeding by a tree species across a whole area, at intervals of several years, followed by lean years. Animals tied to a mast cycle breed only in good years — kākāpō breed when rimu trees mast, which is every two to four years.
Metamorphosis: A marked change in body form between life stages. Complete metamorphosis passes through egg, larva, pupa and adult, as in butterflies and beetles; incomplete metamorphosis has no pupal stage, so a nymph grows gradually into an adult, as in mantises and grasshoppers.
Moult — also Molt: Shedding and replacing feathers, fur, skin or an exoskeleton. Arthropods must moult to grow at all, which makes moulting a dangerous, vulnerable period — a praying mantis without enough vertical space to hang from will moult badly and may die.
Ossicone: A bony, skin- and fur-covered horn-like structure on the skull, found only in giraffes and okapi. Unlike true horns or antlers, ossicones form from cartilage that ossifies and fuses to the skull, and are never shed.
Prehensile: Capable of grasping and holding. A prehensile tail can support an animal's weight and function as a fifth limb; among the whole order Carnivora only the kinkajou and the binturong have one.
Sexual dimorphism: Consistent difference in size, colouring or form between males and females of the same species. Lions show unusually strong dimorphism — males are far heavier and carry a mane — while in many birds of prey the female is the larger sex.
Subspecies: A geographically distinct population within a species, differing consistently in appearance or genetics but still able to interbreed with other populations. Conservation status is often assessed at subspecies level — the migratory monarch butterfly is Vulnerable while the species as a whole is Least Concern.
Taxonomy: The science of naming and classifying organisms into a nested hierarchy — kingdom, phylum, class, order, family, genus, species. Taxonomy changes as genetic evidence accumulates, which is why species counts and relationships shift over time.
Torpor: A short-term drop in body temperature and metabolic rate to save energy, typically lasting hours rather than months. Hibernation is prolonged torpor through winter; aestivation is the equivalent state used to survive heat and drought.
Viviparous: Giving birth to live young rather than laying eggs. Most mammals are viviparous, as are all scorpions and some snakes, lizards and fish. The opposite, laying eggs, is oviparous.

Animal groups

Arachnid: An arthropod of the class Arachnida — spiders, scorpions, ticks, mites and harvestmen. Arachnids have eight legs and two body regions, and lack the antennae and wings that insects have.
Cephalopod: A member of the mollusc class Cephalopoda — octopuses, squid, cuttlefish and nautiluses. Cephalopods have a beak, well-developed eyes and, in most species, the ability to change skin colour and texture rapidly.
Cetacean: A whale, dolphin or porpoise. Cetaceans are fully aquatic mammals that breathe air, give birth to live young and nurse them, and are divided into the baleen whales, which filter-feed, and the toothed whales, which echolocate and catch individual prey.
Corvid: A member of the crow family, Corvidae — crows, ravens, magpies, jays, jackdaws and rooks. Corvids are among the most cognitively capable birds studied, with documented tool use, planning and individual recognition.
Invertebrate: Any animal without a vertebral column. Invertebrates are not a single evolutionary group — the word simply means everything that is not a vertebrate — and they account for roughly 97% of all described animal species. Invertebrate guides
Marsupial: A mammal that gives birth to very undeveloped young which then complete their development attached to a teat, usually inside a pouch. Kangaroos, koalas, wombats, possums and Tasmanian devils are marsupials.
Monotreme: An egg-laying mammal. Only five species survive — the platypus and four echidna species — and they retain the ancestral mammalian trait of laying eggs while still producing milk for their young.
Mustelid: A member of the weasel family, Mustelidae — weasels, stoats, otters, badgers, martens, wolverines and honey badgers. Mustelids are typically long-bodied carnivores with well-developed scent glands.
Raptor — also Bird of prey: A bird that hunts vertebrate prey using hooked bill and gripping talons, with forward-facing eyes for depth perception. Eagles, hawks, falcons, kites, buzzards, ospreys and vultures are raptors; owls hunt the same way at night but belong to a separate lineage. Birds of prey
Ungulate: A hoofed mammal. Even-toed ungulates bear weight on two toes and include deer, cattle, pigs, giraffes and — genetically — whales; odd-toed ungulates bear weight on one or three toes and include horses, rhinos and tapirs.

Giving & governance

Asset lock: A statutory restriction keeping an organisation's assets and any surplus dedicated to its stated community purpose, so they cannot be distributed for private gain. It is a defining feature of the UK Community Interest Company form. Registration status
Gift Aid: A UK tax scheme letting registered charities reclaim basic-rate tax on donations from UK taxpayers, adding 25p per £1 given. It requires charity registration with HMRC, so organisations that are not registered charities cannot claim it. Registration status
Grant-making: Funding another organisation to deliver work rather than delivering it yourself. WARN is a grant-making organisation: it raises funds and makes grants to vetted frontline partners who run the rescue, veterinary and sanctuary work in their own countries. Our work
Restricted donation: A gift the donor has designated for a particular appeal, species or programme, which the organisation is then obliged to spend on that purpose. It offers donors certainty but limits the organisation's ability to respond to changing need.
Unrestricted donation: A gift that is not tied to a specific appeal, species or project, so the organisation can direct it to whatever need is most urgent. Unrestricted funding is generally the most useful kind, because it can move to an emergency instead of sitting against one cause. Where your money goes

Every term, A–Z

All 76 terms in alphabetical order. Select one to jump to its full definition above.

Glossary: common questions

What do the IUCN Red List categories mean?

From lowest to highest risk: Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild, and Extinct. Species with too little information are Data Deficient, and those never assessed are Not Evaluated. Vulnerable, Endangered and Critically Endangered are the three "threatened" categories.

What is the difference between endangered and critically endangered?

Both are IUCN threatened categories, but Critically Endangered is the more severe, applied to species facing an extremely high risk of extinction in the wild. Endangered species face a very high risk. The distinction is set by quantitative thresholds for population size, rate of decline and geographic range.

What does CNVR stand for?

Catch-Neuter-Vaccinate-Release. It is the World Health Organization-endorsed humane method for managing free-roaming dog populations: dogs are caught, sterilised, vaccinated against rabies, marked and returned to their own territory. Over time it stabilises then reduces the population and breaks rabies transmission, which culling does not achieve.

What is the difference between CITES Appendix I and Appendix II?

Appendix I covers species threatened with extinction, where commercial international trade is generally prohibited and permits are granted only in exceptional cases such as research. Appendix II covers species that could become threatened unless trade is controlled; commercial trade is allowed with an export permit confirming legal origin and no harm to the wild population.

Does "Least Concern" mean a species is safe?

Not necessarily. Least Concern describes global status, and a widespread species can be in steep decline regionally. Barn owls are Least Concern worldwide while falling sharply across intensively farmed landscapes, and population trend often matters more than the category itself.

Spotted a term we should define?

If we use a word on this site without explaining it, that is a gap we want to close. Tell us and we will add it.

Suggest a term Browse wildlife guides