Brown Tree Snake

Boiga irregularis

Last updated: January 31, 2023
Verified by: AZ Animals Staff
© Janelle Lugge/

Because the brown tree snake's fangs are located in the back of their mouths, they can rarely bite humans and inject venom unless the snake is very large in size.

Brown Tree Snake Scientific Classification

Scientific Name
Boiga irregularis

Read our Complete Guide to Classification of Animals.

Brown Tree Snake Conservation Status

Brown Tree Snake Locations

Brown Tree Snake Locations

Brown Tree Snake Facts

Birds, rates, bats, lizards, and small mammals
Name Of Young
Group Behavior
  • Solitary
Fun Fact
Because the brown tree snake's fangs are located in the back of their mouths, they can rarely bite humans and inject venom unless the snake is very large in size.
Most Distinctive Feature
Slender body and tail
Other Name(s)
brown cat snakes or culepla
Incubation Period
90 days
Tropical and subtropical environments
Diet for this Fish
Average Litter Size
4 to 12 eggs
  • Nocturnal
Common Name
Brown tree snake
Australia, Papua New Guinea, Indonesia

Brown Tree Snake Physical Characteristics

  • Brown
  • Green
Skin Type
10 to 15 years
5 pounds
4-8 feet
Age of Sexual Maturity
3 to 4 years

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View all of the Brown Tree Snake images!

The brown tree snake is often referred to as the Brown cat snake, and they occur in Australia, Indonesia, and Papua New Guinea.

You can identify these snakes by their vertical cat-like pupils, hence the nickname. In addition, they have large heads and slender bodies and are active nocturnal predators.

The brown tree snake is an invasive species because of their adverse effects on indigenous fauna, which may cause the extinction of many native species. Researchers observed this behavior when these snakes were originally introduced to Guam in the 1940s.

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Because these snakes reproduce throughout the year, their population numbers are experiencing sustainable growth. In addition, the brown tree snake is not a significant threat to humans because they are only mildly venomous.

Amazing Facts About Brown Tree Snakes

  • These snakes are known for their bad tempers and will repeatedly strike if cornered or threatened.
  • The brown tree snake’s fangs are located in the back of their mouths, making biting humans and injecting venom difficult unless the snake is very large in size.
  • Their limited diet consists of small mammals and birds, but juveniles like to prey on small lizards.

Where to Find Brown Tree Snakes

Brown tree snakes are native to Australia, Papua New Guinea, and the Solomon Islands. However, in the 1950s, scientists discovered them on the island of Guam. In addition, people reported seeing them in Texas, Oklahoma, and Hawaii, but this has never been proven.

These snakes are highly adaptable, and their habitats vary significantly over a wide range of tropical and subtropical environments on several islands.

In Guam, they are an invasive species as their presence is causing a severe ecological impact on the native lizard and bird species on the island, who act as pollinators. Because of this, there has been a significant decline in native plant species in Guam.

Brown Tree Snake Scientific Name

The brown tree snake’s scientific name is Boiga irregularis, and they belong to the order Squamata, which means “scaly or having scales.” Squamata is the largest order in the class Reptilia and includes members like:

  • Lizards
  • Snakes
  • Amphisbaenians, also called worm lizards

The Squamata order contains over 11,500 species. In addition, it is the second-largest order of living vertebrates. Their most distinguishable feature is they have horny scales or shields.

Brown tree snakes are members of the Family Colubridae, which contains some of the most common snake species. You can identify them by the complete absence of hind limbs and their lack of teeth on the premaxilla. In addition, most species in this family have very few head scales, a loose facial structure, and ventral scales as broad as their bodies.

Brown Tree Snake Population and Conservation Status

Brown tree snakes are a common species, and their population numbers are stable. The IUCN REDlist lists them as Least Concern, but the exact number of their population is unknown.

Identifying Brown Tree Snakes: Appearance and Description

Brown tree snake head shot accentuates eyes
Brown tree snakes have large eyes that resemble a cat’s.

©Matt Cornish/

Brown tree snakes are slender and agile. Their fangs sit in the back of their mouths; opisthoglyphous is the name of this strange characteristic. But other distinguishing features of their vertical, cat-like pupils, their heads are larger than their bodies, and these snakes come in a wide variety of colors, the most common including:

  • Brown
  • Green
  • Brown with crossbands

However, they also come in red, yellow, or cream colors.

This snake can grow up to 4-8 feet long. However, some of the brown tree snakes located on Guam measured as long as 10 feet, similar to the Lancehead snake’s length. In addition, these snakes weigh up to 5 pounds by the time they are fully grown.

Types of Tree Snakes

There are several types of tree snakes, including:

Australian Tree Snake (Dendrelaphis punctulatus)

The Australian tree snake is often referred to as the green tree snake, and they belong to the Family Colubridae. These diurnal snakes have large eyes, slender bodies and are non-venomous.

They are native to many regions in Australia, specifically along the northern and eastern coastlines, up to Papua New Guinea. The Australian tree snake’s most distinguishing feature is its slender body and tail, which make this snake incredibly agile.

The top of their slender bodies vary in color from golden yellow, olive green, bright green, black, and sometimes blue. However, their bellies and throats are usually pale yellows with blue flecks on their flanks.

Their large eyes generally have golden irises with large, round pupils. Australian tree snakes occur in rainforests, woodlands, and urban areas, and they prey on smaller animals like frogs and fish.

These snakes do not constrict their prey, nor are they venomous. Instead, they rely on their sharp set of teeth to chew the prey and plunge it down their esophagus.

Blunt-headed Tree Snake (Imantodes cenchoa)

The blunt-headed tree snake occupies the forests of South America. These snakes have incredibly broad heads when compared to other tree snakes, and their eyes are large with cat-like vertical pupils.

Paradise Tree Snake (Chrysopelea paradise)

Paradise tree snakes are often referred to as the paradise flying snake, and they are native to southeastern Asia. They belong to the Genus Chrysopelea, which consists of snakes that can glide from the tops of trees by stretching their bodies into flattened ribbon-like strips using their ribs.

They primarily occur in moist forests and can travel distances of 32 feet while gliding from the tops of trees. While performing this amazing skill, their bodies remain relatively stable, suggesting some form of controlled flight.

Paradise tree snakes are mildly venomous, but because of their rear fangs, they are not considered dangerous to humans. Instead of using venom, they constrict their prey and like to feed on lizards and bats.

Venom: How Dangerous are Brown Tree Snakes?

The brown tree snake has quite a reputation as one of the most aggressive invasive species. However, their bite is not dangerous to adults but can cause a reaction in children. Typically, the brown tree snake reacts by striking its target repeatedly when under threat or cornered.

These aggressive snakes are only mildly venomous, and there are no recorded deaths resulting from their bite. However, children have had reactions to their venom, but none were fatal.

Brown Tree Snake Behavior

Not much is known about the brown tree snakes’ behavior. For example, researchers are still unsure whether they live a solitary life or in groups. However, they have managed to figure out that the brown tree snake males live on their own for most of their lives. In addition, they hibernate in abandoned animal burrows during the winter months.

Brown Tree Snake Diet

These snakes typically live in trees, and they like to prey on smaller animals, like:

Brown Tree Snake Reproduction

These snakes keep their population numbers consistent because they reproduce all year round. In addition, and female brown tree snakes can lay 3 to 12 clutches per year! These snakes lay their eggs in hollow logs, caves, or rock crevices, and the clutches appear leathery in texture.

The snakelets hatch after 90 days of incubating, and the offspring measure around 19 inches long. In addition, these snakelets take three to four years to reach sexual maturity. The brown tree snake has no paternal instincts, and once females have laid their eggs, they leave them to fend for themselves.

These snakes have a relatively long lifespan of  10 – 15 years in the wild.

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About the Author

I am a 33-year-old creative and professional writer from South Africa. Wildlife is one of my greatest passions and led me to become the writer I am today. I was very blessed to work with an abundance of wildlife (mainly big cats) and captured my unique experiences in writing. But I wanted to take it further, and I ventured into the freelancing world. Now, I get to spend my days writing about animals; what could be better?

Brown Tree Snake FAQs (Frequently Asked Questions) 

Are brown tree snakes in the United States?

There have been reported sightings in Texas, Oklahoma, and Hawaii, but this has never been proven.

What is another name for the brown tree snake?

Brown tree snakes are also called brown cat snakes or culepla.

Are brown tree snakes aggressive?

The brown tree snake has quite a reputation as one of the most aggressive invasive species. However, their bite is not dangerous to adults but can cause a reaction in children.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.

  1. Wikipedia, Available here:
  2. Invasive Species Info, Available here:
  3. Kidadl, Available here:,they%20are%20nocturnal%2C%20active%20predators.
  4. IUCN Redlist, Available here:

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