Reptile glossary
Reptile keeper terms, explained
Every hobby has its jargon. Here are the reptile-keeping words in plain language — no gatekeeping, no assumed knowledge. 45 terms, each linked to the guide or tool that goes deeper.
Updated July 2026
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☀️ Heat & UVB
Basking spot The basking spot is the warmest surface directly under the heat lamp, where a reptile positions itself to warm up, digest, and (with UVB overhead) get its ultraviolet. Ferguson Zone UVI · UV Index A Ferguson Zone is a classification (1 to 4) of how much UVB a reptile species needs, based on how much sun it basks in the wild — measured as a target UV Index (UVI) at the basking spot. Photoperiod Photoperiod is the daily length of light vs dark a reptile gets — usually set to roughly 12 hours on / 12 off, and adjusted seasonally for species that brumate. Thermal gradient A thermal gradient is the range of temperatures across an enclosure — a warm basking end and a cool end — that lets an ectothermic reptile move between them to regulate its own body temperature. Thermostat A thermostat is a controller that regulates a heat source to a set temperature, preventing an enclosure from overheating — essential safety equipment for any heat lamp or heat mat. UVB UVB is the band of ultraviolet light reptiles need to make vitamin D3 in their skin, which lets them absorb calcium — without it, most reptiles develop metabolic bone disease.
🦎 Anatomy & biology
Autotomy Tail dropping Autotomy is the ability of many lizards (like leopard geckos and crested geckos) to deliberately drop their tail to escape a predator — the tail wriggles as a decoy while the lizard flees. Cloaca Vent The cloaca (or vent) is the single rear opening a reptile uses for waste, mating and egg-laying — its shape and the area just behind it are often how adults are sexed. Ecdysis Shedding · Sloughing Ecdysis is the normal process of shedding old skin — snakes usually shed in one piece, while lizards shed in patches — driven by growth and needing the right humidity to go smoothly. Femoral pores Preanal pores Femoral (and preanal) pores are a row of small openings on the underside of a lizard's thighs that are noticeably larger in mature males — one of the most reliable ways to sex many lizards. Heat pits Loreal pits · Labial pits Heat pits are specialised organs (rows of pits along the lips in pythons and boas) that sense infrared "heat", letting a snake detect warm-blooded prey in the dark. Hemipenes Hemipenes are the paired male reproductive organs in snakes and lizards, stored inverted inside the tail base behind the vent — which is why males often have a thicker, longer tail base. Jacobson's organ Vomeronasal organ Jacobson's organ (the vomeronasal organ) is a scent-detecting organ in the roof of the mouth that reptiles use to "taste" the air — which is why snakes and many lizards flick their tongues. Spectacle Eye cap · Brille The spectacle (eye cap or brille) is the clear scale that covers and protects a snake's (and some geckos') lidless eye — it sheds along with the skin.
🩺 Health
Dysecdysis Stuck shed · Retained shed Dysecdysis is an abnormal, incomplete shed — skin (or an eye cap, or toe/tail tips) that fails to come off — most often caused by humidity being too low. Dystocia Egg-binding Dystocia (egg-binding) is when a female cannot pass her eggs — a life-threatening emergency signalled by a gravid female straining without laying, going off food, and becoming lethargic. Impaction Impaction is a blockage of the gut, often from swallowed loose substrate, oversized prey, or (underlying it) dehydration, low temperatures or poor UVB — a potentially fatal problem. Metabolic bone disease MBD Metabolic bone disease (MBD) is a weakening and deformation of the skeleton caused by a lack of calcium or vitamin D3 — usually from missing UVB or unsupplemented food — leading to soft, bendy bones and a rubbery jaw. Mites Mites are tiny parasitic arthropods (often seen as moving black/red dots, especially around the eyes and vent) that feed on a reptile's blood and spread easily between animals. Mouth rot Infectious stomatitis Mouth rot (infectious stomatitis) is a bacterial infection of the mouth — swelling, redness, or a cheesy yellow discharge around the gums — that needs veterinary treatment. Prolapse A prolapse is when internal tissue (part of the gut, or a hemipenis) protrudes from the vent — always an emergency that needs an exotics vet straight away. Quarantine Quarantine is housing a new reptile separately, in a simple easy-to-clean setup, for several weeks (often 1–3 months) before it goes near your other animals — to catch parasites or disease first. Respiratory infection RI A respiratory infection (RI) is an infection of a reptile's airways/lungs, shown by open-mouth breathing, mucus, wheezing or clicking — usually triggered by wrong temperatures or humidity, and needing a vet. Scale rot Scale rot is a skin/scale infection on the belly — discoloured, blistered or ulcerated scales — usually caused by a substrate that's too wet or dirty, and needing husbandry fixes and often a vet.
🏠 Setup
Bioactive A bioactive vivarium is a living, self-cleaning setup where a "cleanup crew" of isopods and springtails plus live plants break down waste — beautiful, enriching, and low-maintenance once established. Cleanup crew CUC · Isopods · Springtails The cleanup crew (CUC) is the team of tiny invertebrates — usually isopods and springtails — that live in a bioactive enclosure and eat waste, mould and dead plant matter, keeping it clean. Cohabitation Cohab Cohabitation (cohab) is housing more than one reptile together — which for the vast majority of pet reptiles is discouraged, because it causes stress, competition, and hidden bullying. Humid hide A humid hide is a small enclosed shelter filled with damp moss or substrate that gives a reptile a pocket of high humidity — essential for clean shedding, especially in otherwise-dry species. Substrate Substrate is the material lining the floor of the enclosure — chosen to suit the species (e.g. a soil/sand mix for a desert digger, a moisture-holding mix for a humid species), and to allow natural behaviour like burrowing.
🤔 Behaviour
Arm waving Arm waving is the slow, circular lifting of one front leg seen in bearded dragons — a submissive "I see you, I'm no threat" signal, usually acknowledging another dragon (or its own reflection). Brumation Brumation is a reptile's version of hibernation — a cool-season slow-down where it becomes inactive and stops eating in response to shorter, cooler days. Glass surfing Glass dancing Glass surfing is when a reptile repeatedly climbs or scratches at the enclosure glass — often a sign of stress, an over-bright or too-small setup, seeing its reflection, or wanting different temperatures. Head bobbing Head bobbing is a fast up-and-down head movement (common in bearded dragons and other lizards) used to communicate — a dominant or territorial "I'm here" display, or part of courtship. In blue Opaque · Blue phase "In blue" describes a snake about to shed, when its eyes turn milky blue and its colours dull because the spectacle and skin are separating from the new layer beneath. Thermoregulation Thermoregulation is how a reptile controls its body temperature behaviourally — moving between the warm basking spot and the cool end of its thermal gradient because, as an ectotherm, it can't generate its own heat.
🍽️ Feeding
Dusting Supplementation Dusting is coating feeder insects in a fine calcium (and sometimes vitamin/D3) powder just before feeding, to supply minerals reptiles can't get from insects alone. Frozen/thawed F/T Frozen/thawed (F/T) refers to feeding snakes rodents that were humanely pre-killed and frozen, then fully thawed and warmed before offering — safer than live prey, which can injure the snake. Gut-loading Gut-loading is feeding your feeder insects a nutritious diet for 24–48 hours before offering them, so those nutrients pass on to your reptile. Power feeding Power feeding is deliberately overfeeding a reptile (often kept extra-warm) to force fast growth — a discouraged practice that leads to obesity, fatty liver disease and a shorter life. Prey-size rule The prey-size rule is the guideline that a food item should be no bigger than the space between a reptile's eyes (for insects) or about the width of a snake at its thickest (for rodents) — to prevent choking and impaction.
🥚 Breeding
Gravid Gravid is the reptile term for "pregnant" — a female carrying eggs (or, in live-bearers, developing young) — recognisable by a swollen abdomen, weight gain, and often going off food and digging. Slug Infertile egg A slug is an infertile egg — often yellowish, undersized or misshapen — which females can lay with no male present; normal and no cause for alarm on its own.
🧬 Genetics
Het Heterozygous Het (short for heterozygous) means an animal carries one copy of a recessive gene without visually showing it — so a "het albino" looks normal but can pass albino on to its offspring. Morph A morph is a colour, pattern or trait variant of a species produced by selective breeding — like an albino corn snake or a translucent leopard gecko — usually cosmetic and cared for the same as the normal form.