Check Out These Ssseriously Cool Brown Tree Snake Facts

Discover the Brown tree snake native habitat with these Brown tree snake facts.

There are several unknown facts about snakes; here, we throw some light on Brown treesnakes (Boiga irregularis). Commonly known as Brown catsnakes, these tree snakes are native to Papua New Guinea, Australia, and Indonesia. These rear-fanged snakes are distinguished by their vertical cat-like pupils, slender bodies, and large heads, they are nocturnal, active predators. These snakes are a startling example of adverse effects on indigenous fauna leading to the extinction of many native range species; this was an observation made when they have accidentally introduced them to Guam in the 1940s. Their ability to reproduce throughout the year has led to their sustainable growth.

Brown tree snakes are mildly venomous, so they may not be a significant threat to human beings. However, this reptile impacted Guam’s economy and people unprecedentedly. The spotting of these snakes has become so common in this region that the property values have declined with businesses and people relocating. Many organizations are involved in conducting research on how to control the population of snakes, including Princeton University, the U.S. Geological Survey, and the National Zoological Society.

If you enjoy reading these exciting facts about the Brown tree snakes, do check out more such articles on the reticulated python and green anaconda.

Brown Tree Snake

Fact File

What do they prey on?

Lizards, birds, bats, and rats, and other small rodents

What do they eat?


Average litter size?

4-12 oblong eggs

How much do they weigh?

5 lb (2.3 kg)

How long are they?

4-8 ft (1-2 m)

How tall are they?


What do they look like?

Brown to olive green with a red or yellow tinge

Skin Type

Scales with irregular cross-bands

What are their main threats?

Monitor lizards and feral cats and pigs

What is their conservation status?

Least Concern

Where you'll find them

Caves, trees, and near limestone cliffs in grasslands and tropical forests


The eastern and northern coasts of Australia, Papua New Guinea, eastern Indonesia, Guam, and many islands in northwestern Melanesia





Scientific Name

Boiga irregularis





Brown Tree Snake Interesting Facts

What type of animal is a brown tree snake?

The Brown tree snake (Boiga genus) is an arboreal snake from the family Colubridae. They are known as one of the most aggressive invasive species globally.

What class of animal does a brown tree snake belong to?

The Brown tree snake (Boiga irregularis) belongs to the Reptilia class. They are a part of the Scaled reptiles order.

How many brown tree snakes are there in the world?

The population of Brown tree snakes is not currently recorded, but they are considered very common in their habitats. These notorious invasive species' numbers are particularly well documented in the island of Guam; In many parts, the Brown tree snake population size is about 12,000–15,000 per square mile in the 1970s and 1980s. Studies from the early 21st century have found 4,000–10,000 per square mile across the island.

Where does a brown tree snake live?

The Brown catsnake is native to the eastern and northern coasts of Australia, Papua New Guinea, the Solomon Islands, eastern Indonesia, and few islands in northwestern Melanesia. This snake was first discovered on the island of Guam in the 1950s. They have been reportedly sighted (but not confirmed) in Texas, Hawaii, and Oklahoma.

What is a brown tree snake's habitat?

Known to be highly adaptable, the Brown tree snake habitat includes a wide range of subtropical and tropical environments among various islands of its native distribution. When the Brown catsnakes were accidentally introduced to Guam via cargo, it caused a severe cascading ecological impact by local extinction of the island's lizard species and native bird species, native pollinators of Guam. It created a subsequent decline of native plant species.

Who do brown tree snakes live with?

It is not exactly clear whether the Boiga irregularis live in groups or alone, but adult male snakes are solitary most of the time. During the winter months, they may remain in their burrows for up to four months.

How long does a brown tree snake live?

Brown tree snake's lifespan is reported to range between 10-15 years.

How do they reproduce?

One of the advantages these snakes have is that they can reproduce year-round to keep their population growth consistent. Males are observed to store sperm throughout the year, suggesting aseasonal spermatogenesis. However, this could be debatable as most tropical snakes follow seasonal cycles. These animals reproduce by mating where males inseminate females. Females lay 3-12 clutches per year, they lay these leathery-shelled clutches of eggs in hollow logs, rock crevices, or caves. After approximately 90 days, the offsprings come out 50 cm long. These snakes take about three or four years to reach sexual maturity. Female populations are not known to incubate their eggs or take care of the young; these hatchlings fend for themselves as soon as they come out of the eggs.

What is their conservation status?

Brown catsnakes are not considered endangered or threatened. They are good in numbers so far and could pose a substantial threat to the native species when introduced to newer habitats.

Brown Tree Snake Fun Facts

What do brown tree snakes look like?

Agile and slender, the Brown tree snake description has to include the distinguishing rearward (opisthoglyphous) fangs, head larger to the body, vertical cat-like pupils, and a long tail. Depending on their region, they have a wide variety of colors but are most commonly seen in brown color, greenish, or brownish coloring with cross-bands. Sometimes, they have been spotted in pink, red, yellow, and creamy white colors.

Read our Guam Brown tree snake, known as the Brown tree snake, facts.

How cute are they?

Although these snakes are slender-looking than most big snakes, this snake is not particularly attractive in terms of looks. It is mostly associated with the trouble it has caused to the native species in the habitat it was introduced to and the people by causing damage to power outages by electrocuted snakes cost close to $4 million yearly.

How do they communicate?

There are no reports on their interaction between themselves or with humans. There is very little known about Brown tree snake characteristics. They react swiftly to sudden movements, and more research is needed on Boiga irregularis' perception and communication.

How big is a brown tree snake?

The Brown tree snake (Boiga irregularis) can grow up to 4-8 ft (1-2 m) in length. Some of them on the Pacific islands of Guam are found to be more than 10 ft (3 m) long, close to Lancehead snakes' size.

How fast can a brown tree snake move?

These nocturnal species are agile and fast using movements such as lasso locomotion. Their slender body boasts climbing ability; hence, they can pass through tiny spaces in shaded locations, hollow logs, rock gaps, and buildings. They spend their time hanging on the trees or jumping between branches.

How much does a brown tree snake weigh?

Adult Boiga irregularis (Brown tree snakes) can weigh up to 5 lb (2.3 kg) once fully grown.

What are their male and female names of the species?

The Boiga irregularis (Brown treesnake) does not have any specific names for their male and female species. You may have heard of the name Storeria, a common name given to brown snakes in North America. Storeria means shy, small, non-venomous snake.

What would you call a baby brown tree snake?

There is no known name for a baby Brown tree snake (Boiga irregularis). The newborns are usually called hatchlings. They come out of oblong eggs with 42–47 mm in length and 18–22 mm in width.

What do they eat?

This active predator, Brown treesnake, is found in arboreal habitats. They prey on rats, lizards, skinks, forest birds, geckos, and other available vertebrates and small mammals. They consume 70% of their body mass; this large meal is unusual for a colubrid snake.

Are they dangerous?

The Brown treesnake is considered one of the most aggressive invasive species. However, the Brown tree snake bite is not considered dangerous to adults, but some reactions are seen in young children. Usually, these snakes react violently by striking repeatedly only when they sense a threat from people.

Would they make a good pet?

The Brown treesnake is not a snake for beginners. If you have some experience previously handling snakes, you can try to get a Brown tree snake (invasive species by nature) but be cautious about some of the risks that come with Brown tree snake venom. They have numerous teeth but use the last two on each side of the upper jaw to inject venom as it bites. Typically, these bites cannot penetrate most clothing.

Did you know...

The Brown treesnakes hunting is an interesting watch. The brown treesnake first bites before wrapping its own body around the victim to immobilize the prey. It then initiates chewing to inject venom; this venom has little effect on most mammals than on vertebrates.

On the contrary, there is no reliable documentation on the predators of the Brown tree snake. It is perceived that they are preyed upon by feral pigs and cats, monitor lizards, and sometimes vulnerable to cane toads (Bufo marinus) and red-bellied black snakes (Pseudechis porphyriacus).

How did the brown tree snake get to Guam?

Native to Papua New Guinea, the brown treesnake was accidentally transported in cargo ships to the South Pacific to Guam shortly after World War II. There, with no natural Brown tree snake predators, this native forest animal soon established itself throughout the island, which later became responsible for a steep decline in its biodiversity due to this snake on Guam. This arboreal predator caused the extinction of the Micronesian kingfisher and Guam rail and the disappearance of nine of the eleven avifauna species in Guam.

There have been discussions of many techniques to eliminate these Brown treesnakes, but there is no established way to remove them entirely. Research and efforts are underway on tools such as toxicants, fumigants, attractants, and improved traps. Traps have been proven most effective technique to control these invasive reptiles. Rapid Response Team (RRT), a multi-agency, was established in 2002 to assist in capturing and detecting these treesnakes on recipient islands. The US government spends an estimated $8,000,000 annually on a 'tiny assassins' program that involves dropping mice laced with Paracetamol from airplanes to control this invasive snake population density.

Why has the brown tree snake been so successful?

The introduced species of Brown tree snakes on Guam, a region with no natural predators, the absence of natural population controls, and the abundance of vulnerable prey started their success. Guam is a small remote island with limitations on prey escaping their predators, where the Brown tree snake benefits. In the invasive snake's native range, restricted food availability kept their populations under check; in Guam, the abundance of fast-breeding lizard species make up for their primary diet. Additionally, the non-seasonal climate in Guam is the most favorable condition for this animal's reproduction and growth. The Brown catsnake is known to grow up to an unusual length of three meters on this island and it has now reached populations of up to 30,000 per square mile. USGS scientists and their staff working on this snake control project are co-located at the Guam National Wildlife Refuge at Guam's northern end.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other reptiles including the mangrove snake, or gopher snake.

You can even occupy yourself at home by drawing one on our snake coloring pages.



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