Monitor Lizard

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Monitor Lizard Care Guide

Varanus spp.

Monitor lizards are a diverse group of powerful, carnivorous lizards native to Africa and Australasia, ranging from terrestrial to arboreal to semi-aquatic. They are known for their exceptional intelligence and engaging personalities, but can be challenging to keep. Commonly kept species include small dwarf monitors such as the Ackie monitor (reaching about 2–2.5 feet), medium-sized species such as the Savannah and tree monitors (reaching about 3 feet), and occasionally large species such as Asian water monitors, Nile monitors, black-throated and white-throated monitors, and crocodile monitors (which can exceed 6–8 feet in length and over 40 pounds).

Like snakes, monitor lizards have a long forked tongue they flick in and out to evaluate their environment and detect prey. Monitors do not exhibit tail autotomy and can use their tail defensively (tail whipping), and can also deliver a painful bite. Some species, such as tree monitors, have a prehensile tail used for navigating their arboreal environment. With proper care, their life expectancy is 10–20+ years.

Please research the specific requirements of your species thoroughly before purchasing one of these animals to ensure those needs can be met.

Enclosure

Enclosure size, style, and furnishings depend on the species. Monitors are active lizards and even smaller species require spacious enclosures that mimic their natural habitat as closely as possible. General minimum enclosure size guidelines:

  • Ackie monitors: 4 ft L × 4 ft W × 2 ft H
  • Tree monitors: 4 ft L × 2 ft W × 4 ft H (taller for climbing)
  • Most larger monitors: 10–12 ft L × 8 ft W × 8 ft H minimum — in many cases an entire room is dedicated to the largest species

Terrestrial and burrowing species need more horizontal space and deep substrate. Arboreal species need more vertical space and sturdy climbing branches. Hollow logs, cork bark flats and rounds, vines, and artificial or live nontoxic plants provide security and enrichment. Front-opening enclosures with a mesh top for ventilation are preferred. Solitary housing is recommended in most cases.

Substrate

Arid species: a ~50:50 mix of organic topsoil and fine sand works well. Excavator clay is also commonly used. Burrowing species such as Ackie monitors require substrate depth of 12–24+ inches to accommodate this behavioral need.

Tropical forest species: moisture-retaining substrates such as blends of coconut fiber/Eco Earth, cypress mulch, organic topsoil, forest floor mix, leaf litter, and sphagnum moss. A drainage layer beneath the substrate is recommended. Bioactive setups are popular and help with waste management but should only be established after an appropriate quarantine period with negative fecal testing.

Do not use calcium sand, walnut shell, large wood chips, cedar/pine shavings, or gravel. Always feed off the substrate to prevent accidental ingestion and impaction.

Temperature

Provide a temperature gradient using a basking bulb or ceramic heat emitter. Specific temperatures vary by species:

  • Ackie and Savannah monitors: 75–100°F ambient, basking ~130°F, no lower than 70°F at night
  • Tree monitors: 78–86°F ambient, basking 95–110°F, no lower than 70°F at night
  • Asian water monitors: 82–90°F ambient, basking 95–110°F, no lower than 70°F at night
  • Black-throated and white-throated monitors: 75–90°F ambient, basking 110–120°F, no lower than 70°F at night
  • Crocodile monitors: 75–90°F ambient, basking 100–120°F, no lower than 75°F at night

Heat sources should not produce light at night to avoid disrupting the photoperiod. Monitor temperatures with a digital probe thermometer or infrared laser thermometer. A reptile thermostat is recommended for safer, more accurate temperature control. Heat rocks should be avoided — they pose a serious risk of severe burns.

Humidity

Humidity requirements vary by species and should be measured with a digital hygrometer. A dehumidifier may be needed for some arid species. Hand misting or an automated misting system such as MistKing can be used to raise and maintain humidity. General guidelines by species:

  • Ackie monitors: 20–50%
  • Savannah monitors: 40–50%
  • Tree monitors: 70–80%
  • Asian water monitors: 60–70%
  • Black-throated and white-throated monitors: 50–70%
  • Crocodile monitors: 70–90%

All species should have access to clean fresh water daily. Species such as the Asian water monitor require a large pool for swimming and soaking — a filtration system and frequent water changes and disinfection are necessary.

UVB Lighting

UVB lighting is essential for monitor lizards to properly absorb calcium from their diet. UVB cannot pass through standard glass — placing an indoor reptile near a window does not provide adequate UVB. Zoo Med or Arcadia brand high-output UVB bulbs are recommended, such as the ReptiSun 10.0, Arcadia Desert 12%, or Arcadia D3 Dragon 14%. The Zoo Med Powersun UVB mercury vapor bulb produces both heat and UVB but should only be used in large enclosures.

  • Fluorescent UVB bulbs should be positioned so the reptile can get within 12–18″ of the bulb — use branches or logs to allow climbing closer if needed
  • Mercury vapor bulbs produce significant heat — place a minimum of 12″ from the basking spot
  • Dense screening can block up to 50% of UVB — multiple bulbs may be needed for enclosures with very dense screens

UVB lighting should be on for 12 hours per day. Replace bulbs every 6–12 months — the UVB-emitting coating wears off even when the bulb still produces visible light.

Diet & Feeding

Monitor lizards are predominantly carnivores, though some species are omnivores or frugivores. Monitors do not chew — they swallow prey whole. Common food choices include crickets, mealworms, dubia roaches, silkworms, grasshoppers, locusts, frozen/thawed rodents, ground turkey, cooked or raw eggs, frozen/thawed fish, and commercial options such as Reptilinks. Diet should be varied and species-appropriate.

  • Juveniles: feed as much as they will eat daily
  • Small adults (e.g., Ackie monitors): 3–5 times per week
  • Medium adults (e.g., Savannah and Asian water monitors): 2–3 times per week
  • Giant species (e.g., crocodile monitors): 1–2 times per week

Feed less frequently for fully grown adults to prevent obesity.

Supplementation:

  • Calcium carbonate (without D3) — e.g., Zoo Med ReptiCal — sprinkled on food 2–3 times weekly
  • Multivitamin containing true vitamin A — e.g., Zoo Med Reptivite — once weekly to once every 2 weeks. If housed indoors, use Reptivite with D3

Enrichment

Enrichment is critical for monitor lizards to provide mental stimulation, exercise, and engagement and to prevent boredom. Environmental enrichment can include climbing branches for semi-arboreal species, dig boxes for burrowing species, pools and water features for semi-aquatic species, and novel items, scents, toys, and tunnels — periodically rearranging the enclosure is also beneficial.

Feeding enrichment can include puzzle feeders, foraging boxes, and hiding food around the enclosure (on branches, in pre-drilled log holes, dangling from a rope, etc.) to encourage natural foraging behavior. Ensure all items are safe, nontoxic, and free of small fragile pieces that could be ingested. Remove uneaten food promptly to prevent spoilage. Target training is also a great way to interact with your lizard.

Veterinary Care

An annual wellness examination and fecal screening for parasites is recommended for all reptiles.