Black Tree Monitor

Explore all 1 supporting guides ↓

Few lizards are as uniformly dark as the black tree monitor. This slender monitor lizard from Indonesia’s Aru Islands is jet black from nose to tail tip. It lives in the rainforest canopy and rarely comes down to open ground.

Among pet lizards it is one of the most striking. It is also a demanding animal, built for the trees, not the coffee table.

As an Amazon Associate, Lizardist earns from qualifying purchases. Some product links on this page are affiliate links.

What Is a Black Tree Monitor?

Varanus beccarii belongs to the monitor lizard family. It sits in the emerald tree monitor group, a set of small, arboreal species from New Guinea and nearby islands.

It was first described in 1874. Researchers named it after the naturalist who collected it, Odoardo Beccari.

For decades it was treated as a color form of the emerald tree monitor. Later work confirmed it as its own species.

What sets this monitor apart is its coloring. The entire body, from nose to tail tip, is a uniform, glossy black.

That look is why some searchers land on this page while thinking of a different dark lizard. A black tree monitor is a distinct species. It is much smaller than the giant Asian water monitor, which some people call a black water monitor.

The body is slim and the neck is long. The limbs end in sharp, curved claws built for gripping bark.

Roughly two thirds of the total length is tail. That tail is prehensile, so it wraps and grips like a fifth limb while the lizard climbs.

Size and Lifespan

Adults reach about 3 to 4 feet in total length, roughly 0.9 to 1.2 meters. Because so much of that is tail, the body itself stays fairly light.

That makes it much slighter than a stocky monitor like the savannah monitor. In the wild, black tree monitors live up to about 15 years, according to Smithsonian’s National Zoo.

Well kept animals in human care can potentially live longer. They face no predators and get steady food and veterinary care.

Keepers and sources vary in the upper number they quote. Firm captive longevity records for this species are still limited.

Care Overview

Caring for this species means recreating a warm, humid, vertical rainforest. It is not a typical lizard tank setup.

Everything should support climbing first and ground space second. This is not a beginner lizard.

It needs a tall, secure enclosure and a strict heating and lighting setup. It also needs a varied insect based diet and an owner comfortable around a fast, sharp clawed animal.

Most keepers who succeed already have experience with other monitors. Many treat the animal as a long term display project rather than a lizard for regular handling.

Anyone weighing whether this is the right lizard should read a general guide to choosing a pet lizard first. A black tree monitor sits well outside beginner territory.

The right reptile supplies need to be ready before the animal comes home. That means a tall enclosure and strong UVB fixtures from day one.

Enclosure Setup

Height matters more than floor space for this species. A published husbandry account of a breeding pair used a tall enclosure. It measured roughly 5 feet 3 inches long, 4 feet wide, and 6 feet tall.

Many keepers build similarly tall setups for a single adult. Fill that vertical space with secure branches, cork bark, and vines at different angles.

That lets the lizard climb, perch, and bask at height. A soft, moisture holding substrate such as coconut fiber or topsoil helps hold humidity and lets the animal dig.

Sturdy hides at both a high point and a low point give the lizard a choice of retreat. Live or artificial plants add cover.

A large water basin is standard. The same husbandry account included a heated soaking basin, and the species readily uses one.

For general layout ideas across arboreal species, a broader lizard enclosure guide is a useful starting point before buying anything.

Heating and Lighting

Black tree monitors come from a warm, equatorial climate. A documented captive setup kept daytime ambient temperatures around 75 to 93 degrees Fahrenheit.

Basking surfaces in that setup exceeded 113 degrees Fahrenheit. Nighttime ambient temperatures dropped to about 72 to 77 degrees Fahrenheit, mirroring a natural day and night swing.

Relative humidity in that same setup ran high, generally 70 to 95 percent. It was kept up with automatic misting running several times a day.

Most keepers aim for a similarly humid, warm range rather than one fixed number. Full spectrum UVB lighting across a large part of the enclosure is standard practice for a sun exposed monitor like this one.

Bulb strength should suit the distance from the animal to the fixture. Some keepers pair UVB with a separate basking bulb, such as an Arcadia Halogen Basking Lamp, to hit the high daytime temperatures this species needs.

Exact numbers vary a bit from one setup to the next. Treat published ranges as a starting point, then fine tune with a thermostat, a thermometer, and a hygrometer.

What Black Tree Monitors Eat

In the wild, black tree monitors are carnivores. They hunt mainly small invertebrates, probing bark and tree crevices with their claws and forked tongue.

They also take small mammals, amphibians, and bird eggs or nestlings when the chance comes up. A published husbandry account found that insects made up more than 90 percent of the captive diet by weight.

That included dubia roaches, beetle grubs, and superworms. Adults in that account were fed once or twice a week, totaling roughly 10 to 20 grams of food per animal each week.

Calcium supplementation on feeder insects, such as Zoo Med Repti Calcium without D3, supported healthy growth in that case, along with an occasional vitamin supplement. Overfeeding is a common mistake among keepers generally.

Captive monitors get far more food, with far less effort spent hunting it, than wild animals ever would. For general feeding principles across the family, see this guide to what lizards eat.

Health and Common Problems

Most health problems in captive monitors trace back to husbandry, not disease that shows up on its own. Low humidity and poor UVB access are common causes of shedding trouble and weak bone growth in arboreal monitors generally.

Obesity is a frequent issue in captivity. Feeder insects are easy to overfeed, and captive animals move less than wild ones.

Keepers should watch body condition rather than feeding on a fixed schedule without adjusting portions. Stress has causes too: handling, an undersized enclosure, or too much foot traffic near the tank. It can show up as poor appetite or hiding.

Watch for a lizard that stops eating for more than a couple of weeks, loses weight, or shows swelling. Labored breathing is another red flag.

This general lizard health guide covers warning signs that apply across species.

Behavior and Temperament

Black tree monitors are solitary, highly alert animals. Most sources describe them as one of the more intelligent monitor species.

They spend most of their time climbing, exploring, and investigating their surroundings. That makes them fascinating to watch, but not a lizard that sits still for handling.

Males are territorial and will rear up on their hind legs to grapple with rivals. This dominance display sometimes shows up in captivity between two housed males.

For that reason, adult males are usually kept alone or only introduced to a female under supervision. Juveniles tend to be flighty and quick to bolt or bite when startled.

Many individuals never become fully comfortable with regular handling. Keepers who succeed long term usually focus on slow, low pressure interaction and treat the animal as an active display species.

Breeding

In the wild, females lay clutches of 3 to 7 eggs, sometimes twice a year. Eggs are laid in elevated nest sites such as tree hollows or termite mounds.

Reported incubation lengths run from about 161 to 164 days, a notably long stretch for a lizard. A documented captive breeding involved repeated matings over about a week in midwinter.

That pairing produced a clutch of three eggs, incubated at about 87 degrees Fahrenheit and roughly 95 percent humidity. Only one of those three eggs produced a surviving hatchling.

That result shows how demanding this species is to breed, even with careful conditions. Breeding this species takes real experience with monitor husbandry first.

A poorly conditioned female or an unstable incubation setup can end a clutch. Anyone new to the species is better off mastering day to day care before attempting to breed.

Cost and Availability

Black tree monitors are less commonly available than mainstream pet lizards. Prices vary by breeder, age, and whether the animal is proven captive bred stock.

Because the species is listed under CITES Appendix II, legitimate sellers should be able to show captive bred documentation. Wild caught animals still enter the trade under export quotas, so ask before buying.

Beyond the purchase price, budget for a large, tall enclosure and strong UVB and heating equipment. An ongoing insect based diet adds up too, and together these often cost more over time than the animal itself.

A dedicated setup built for a full grown adult from the start usually works out cheaper than repeatedly upgrading a smaller tank. Buying only from breeders who can document captive bred lineage supports wild populations on the Aru Islands.

It also generally means a healthier, better started animal.

Where Black Tree Monitors Come From

This species is endemic to the Aru Islands, off the southwest coast of New Guinea in Indonesia. It lives in tropical forest and mangrove swamp.

It spends most of its time in the canopy, descending mainly to forage or move between trees. The IUCN lists the species as Data Deficient.

That means there is not enough population data for a full risk assessment, though the population trend is considered to be declining. Habitat loss from deforestation, along with capture for the pet trade, are the main pressures described for wild populations.

Because of that, and because of its CITES Appendix II listing, supporting captive breeding programs matters more here than for common pet lizards. Keepers curious how it compares with relatives can look at the emerald tree monitor, the crocodile monitor, or the far larger Nile monitor on the wider monitor lizards overview.

Frequently Asked Questions

Is a black tree monitor the same as a black water monitor?

No. This species is small, slender, and fully arboreal, native to the Aru Islands.

The animal sometimes called a black water monitor is usually a dark colored Asian water monitor, a much larger, mostly ground and water dwelling species from a different part of the region.

How big does a black tree monitor get?

Adults reach about 3 to 4 feet in total length, roughly 0.9 to 1.2 meters. Most of that length is tail, so the body stays fairly slender even at full size.

Are black tree monitors good pets for beginners?

Generally not. They need a tall, precisely controlled enclosure and an owner comfortable with a fast, sharp clawed, often defensive lizard.

Most keepers who do well with the species already have experience with other monitors first.

What do black tree monitors eat?

In the wild they eat mainly small invertebrates, along with small mammals, amphibians, and bird eggs when available. In captivity, the diet centers on appropriately sized, gut loaded insects, with occasional rodent or egg for variety.

Are black tree monitors legal to own?

In most places, yes, as documented captive bred animals. The species is regulated under CITES Appendix II rather than fully protected.

Buyers should confirm captive bred origin first. Local exotic pet rules also vary by country and by state, so check those too.

How long do black tree monitors live?

In the wild they live up to about 15 years. Animals in human care can potentially live longer, though solid long term captive data is still limited.