Decor
- A network of sturdy branches for climbing
- Artificial plants for aesthetic cover
- Large, shallow water bowl — drinking and bathing
Monitor lizards · Care guide
Black Tree Monitor Care Guide
Varanus beccarii
Endemic to the Aru Islands off New Guinea, this arboreal species lives in humid forests and mangrove swamps. Adults grow 3–4 ft. Plan a tall humid vivarium with a network of sturdy climbing branches, T5 6% UVB, and a large shallow bathing bowl.
At a glance
Quick facts
Key parameters for day-to-day husbandry. Full detail is in the sections below.
-
Daytime probe
80–82 °F
27–28 °C · thermostat sensor target
-
Night drop
10 °F
6 °C below daytime
-
Humidity
60–80%
With a night spike
-
UVB
T5 6%
Ceiling-mounted tube
01 · Housing
Enclosure & housing
Endemic to the Aru Islands off New Guinea — humid forests and mangrove swamps. Adults grow 3–4 ft. Arboreal: a network of sturdy climbing branches, artificial plants for cover, a high-humidity coir and orchid bark mix, and a large, shallow water bowl for drinking and bathing.
Adult minimum size
48″ W × 24″ D × 60″ H
4 ft × 2 ft × 5 ft high for a single adult. Adults grow 3–4 ft — height matters for this arboreal climber.
Substrate
- Any high-humidity mix
- Coir and orchid bark mixed
Cleaning
- Daily: spot clean to keep the enclosure smelling fresh and limit bacteria
- Every 4–6 weeks: full clean if kept relatively clean — replace substrate, disinfect décor and vivarium, then return clean, dry décor
Housing diagram
Enclosure example
Front view 48″ wide × 60″ tall (depth 24″) · climbing branches · plants · large shallow bowl
- Front proportions — 48″ wide × 60″ tall (4:5); depth 24″ — 4 × 2 × 5 ft
- Branches — a network of sturdy climbing wood
- Plants — artificial plants for aesthetic cover
- Water bowl — large and shallow, for drinking and bathing
- Substrate — high-humidity coir and orchid bark mix
- Heat & UV — basking 100–110 °F (35–38 °C) · T5 6% on the ceiling
Setup diagram · 1 of 2
Top-down view
Heat bulb & probe left–right positions · Recommended temps need this layout
Setup diagram · 2 of 2
Front view
Looking into the vivarium · bulb on the ceiling · probe hangs down the back
- Heat bulb — about one-quarter from one side, halfway front to back (on / through the ceiling)
- Probe — one-quarter from the opposite side, hanging down the back about halfway down
02 · Climate
Temperature & UVB
A tall arboreal setup, a clear gradient, T5 6% UVB, and humidity of 60–80% with a night spike.
Daytime temperature gradient
When the heat bulb and thermostat sensor are placed as instructed, a probe target of 80–82 °F (27–28 °C) creates this spread. The probe point is not the basking spot.
| Zone | Temperature |
|---|---|
| Cool side | 75–78 °F (26–27 °C) |
| Probe point (thermostat probe target) | 80–82 °F (27–28 °C) |
| Middle | 86–88 °F (30–31 °C) |
| Warm side | 90–95 °F (32–35 °C) |
| Basking spot (hottest point under bulb) | 100–110 °F (35–38 °C) |
| Night drop | Reduce thermostat by 10 °F (6 °C) drop |
Photoperiod & night
- Winter: about 12 hours light/heat
- Summer: up to 16 hours when days are longer
- Night: drop temperatures by 10 °F (6 °C)
- Clear day/night temperatures let metabolism slow — essential for rest
UVB lighting
- Recommended T5 unit with 6% UV output on the ceiling
- Mount straight across or diagonally (diagonal often places the power unit toward a rear vent)
- Replace every 12 months — UV output degrades over time
- Match UV on/off to heat schedule (morning on, evening off)
- UVA boosts appetite & activity; UVB enables vitamin D3 / calcium absorption
Humidity & water
Black Tree Monitors need a humid tropical setup. Keep 60–80% humidity by spraying twice a day, with a heavier spray in the evening to create the nighttime spike. A large cool-side water bowl is for drinking and bathing, and also helps hold humidity. Use a high-humidity mix of coir and orchid bark.
Day
60–80%
Ambient humidity
Night
Spike
Heavier spray · overnight rise
- Heavier evening spray to raise humidity a little toward the top of the 60–80% range overnight
- Large cool-side water bowl — drinking, bathing, and humidity support
- Always use de-chlorinated water like Reptishield, never untreated tap water.
Climate diagram
Lighting setup
T5 6% UVB on the ceiling · heat on the warm / basking side
- T5 6% UV unit — ceiling-mounted (straight or diagonal); UVA supports appetite & activity; UVB enables vitamin D3 / calcium absorption
- Heat dome — warm side; basking 100–110 °F (35–38 °C); same on/off routine as UV (morning on, evening off)
- Photoperiod — 12 hours in winter, up to 16 hours in summer
- Replace UV every 12 months — output degrades even if the tube still glows
First power-up tip
Always have the thermostat dial turned down before you plug it into the mains for the first time.
03 · Nutrition
Diet & feeding
Mainly insectivorous, with eggs and mammals, and occasional vegetation in captivity. Dust every feed, gut-load insects well, and use the method of 5 while settling.
At a glance
Feeding cheat sheet
- Type
- Insects · occasional vegetation · eggs and mammals
- Settling
- Method of 5 — feed 5 insects at a time
- Settled
- Often 10–20+ crickets daily · adults may need 1–2 food-free days/week
- Dust
- Every feeding · 4:1 calcium : Nutrobal
- Water
- Large, shallow cool-side bowl · Reptisafe or bottled · drinking, bathing and humidity
Staple insects
Feed regularly · dust every feed
- Crickets, locusts, Dubia roaches
- Calci worms
- Occasional vegetation in captivity
Occasional & meat
In moderation · eggs and mammals
- Wax worms, mealworms, Morios
- Mice
- Eggs
Supplements — every feeding
Dust every feeding — live foods and salads — with a 4:1 mix of calcium : Nutrobal (4 parts calcium to 1 part Nutrobal). Mix first, then coat the food every time you feed.
Settling appetite — method of 5
New Black Tree Monitors are often stressed and may not eat well for the first few days. This is perfectly normal. Until you know their habits, use the method of 5: offer five insects at a time and wait until they are eaten before adding more. That reduces leftover insects that can stress or injure the animal. Once settled, 10–20+ crickets daily is relatively common; adults often need one or two food-free days each week.
Feeding style
- Hunting and chasing food provide exercise and enrichment
- Hand feeding can help bonding — excessive hand feeding can lead to obesity
- Will take eggs and mammals — offer mice and eggs in moderation
Water
- Large, shallow cool-side bowl — drinking, bathing, and humidity
- Reptisafe or bottled water only — never untreated tap
Gut-load insects before offering — variety matters for calcium-to-phosphorus (Ca:P) and vitamins.
Why gut loading matters
Feeder insects must be well fed before offering. In the wild, lizards eat insects that themselves ate a wide variety of foods — providing complete nutrition and a better calcium-to-phosphorus (Ca:P) ratio.
- Use commercial gut-load foods with quality ingredients
- Add fresh reptile-safe vegetables for variety
- A single piece of carrot or potato is not enough — poor Ca:P and limited vitamins/minerals
Speak to a member of staff for more feeding advice.
04 · Behaviour
Handling & behaviour
Arboreal monitors (about 3–4 ft). A smaller species that lives in the branches. Settling and regular feeding come before handling.
- Step 1
Settle first
Allow the Black Tree Monitor to settle and begin eating regularly before handling — we recommend at least two successful feeds first. Adapting is stressful; early handling can make it worse.
- Step 2
Short sessions
Initial sessions: 5–10 minutes only. Lengthen as the monitor becomes more comfortable.
- Hygiene
Wash hands
Always wash or disinfect hands before and after handling to prevent bacteria transfer both ways.
- Warning
No aerosols
Do not use aerosols or plug-in air fresheners near the enclosure — the chemicals can harm your Black Tree Monitor.
05 · Welfare
Health & welfare
Prevention starts with correct husbandry — heat, UVB, hydration, and supplementation working together.
Best prevention: good husbandry
Correct temperatures, supplementation, hydration, and UVB keep the immune system and gut working well — supporting essential physiological processes.
Inert substrates Paper, lino, carpet — pros & cons
Pros
- Lower impaction risk
Cons
- Limit natural behaviours such as digging
- Can increase faecal contamination (waste less absorbed)
Questions
FAQ
What size vivarium does a Black Tree Monitor need?
For a single adult, a minimum of 4 ft × 2 ft × 5 ft high (48″ wide × 24″ deep × 60″ tall). Adults grow 3–4 ft. They are arboreal, so provide a network of sturdy climbing branches, artificial plants for cover, a high-humidity coir and orchid bark mix, and a large, shallow water bowl for drinking and bathing.
What temperatures does a Black Tree Monitor need?
Set the thermostat probe to 80–82 °F (27–28 °C) by day with the heat bulb about one-quarter from one side and the probe one-quarter from the opposite side, hanging down the back about halfway down. That creates a gradient of 75–78 °F on the cool side, 86–88 °F in the middle, 90–95 °F on the warm side, and a basking spot of 100–110 °F under the bulb. At night drop temperatures by 10 °F (6 °C).
What humidity do Black Tree Monitors need?
Aim for 60–80% humidity with a night spike. Use a high-humidity mix of coir and orchid bark, a large shallow cool-side water bowl for drinking and bathing, and a light evening spray. Always treat water with a de-chlorinator such as Reptisafe, or use bottled water.
When can I start handling my Black Tree Monitor?
Allow the monitor to settle and begin eating regularly before handling — we recommend at least two successful feeds first. Initial sessions should be 5–10 minutes only; lengthen as they become more comfortable. Always wash or disinfect hands before and after handling. Do not use aerosols or plug-in air fresheners near the enclosure.
What UVB do Black Tree Monitors need?
A T5 unit with a 6% UV tube mounted on the ceiling — straight across the top or diagonally (diagonal often places the power unit toward a rear vent). Replace the tube every 12 months because UV output degrades. Match UV on/off to the heat schedule: about 12 hours in winter and up to 16 hours in summer.
What do Black Tree Monitors eat?
They are mainly insectivorous. Offer crickets, locusts, Dubia and calci worms as staples; wax worms, mealworms and Morios in moderation. They will take eggs and mammals, and in captivity they occasionally take vegetation. Dust every feed with a 4:1 calcium : Nutrobal mix. Use the “method of 5” while settling; settled animals may take 10–20+ crickets daily. Adults often need one or two food-free days per week. Hunting and chasing food provide exercise and enrichment.
Next steps
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