Tree Snake

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Tree Snake

Boiga irregularis

Last updated: May 23, 2022
Verified by: IMP
Image Credit Matt Cornish/

Though this snake’s venomous bite isn’t harmful to adults, it can be dangerous to children

Tree Snake Scientific Classification

Scientific Name
Boiga irregularis

Read our Complete Guide to Classification of Animals.

Tree Snake Conservation Status

Tree Snake Locations

Tree Snake Locations

Tree Snake Facts

Rats, birds, lizards, bats
Fun Fact
Though this snake’s venomous bite isn’t harmful to adults, it can be dangerous to children
Most Distinctive Feature
Large eyes and vertical pupils
Distinctive Feature
A large head compared to its slender body
Other Name(s)
Cat snake
  • Nocturnal
Common Name
Brown tree snake
Nesting Location
In a crevice or beneath a rock to keep them cool

Tree Snake Physical Characteristics


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View all of the Tree Snake images!

It’s sometimes called a cat snake because of its large eyes and vertical pupils.

The brown tree snake lives in the northern and eastern parts of Australia, on Papua New Guinea, the Solomon Islands as well as on the island of Guam. This snake is large in size sometimes growing to a length of 6.6 feet. It is venomous with fangs located in the back of its mouth. It eats bats, birds, rats, and lizards. It’s considered an invasive species in Guam.

Four Amazing Facts

  • The longest one on record is 9.8 feet
  • It lays four to 12 eggs in a crevice or beneath a rock to keep them cool
  • This snake breeds year-round
  • Though this snake’s venomous bite isn’t harmful to adults, it can be dangerous to children

Where to Find a Tree Snake

These snakes live in Australia, Papa New Guinea, the Solomon Islands, and Guam. They live up to their name by spending a lot of time hunting in trees. They also hunt for prey on the ground. Their habitat includes tropical forests, mangroves, caves, rocky areas, and grasslands. They sometimes show up in homes in suburban areas. These snakes are active at night and breed throughout the year.

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Types of Tree Snakes

These snakes belongs to the Colubridae family. There are 249 genera in this large family of snakes. Not surprisingly, the brown tree snake is not the only type of snake with a tree habitat.

Some other tree snakes include:

  • Paradise tree snake (Chrysopelea paradisi): The paradise snake lives in southeast Asia and is commonly seen in palm trees. At a maximum of 3.9 feet, this snake is much smaller in size than the brown tree snake.
  • Blunt-headed tree snake (Imantodes cenchoa): These snakes live in tropical forests in South America. Both this snake and the brown tree snake have large eyes with vertical pupils. However, the blunt-headed snake has a remarkably wide head whereas a brown tree snake’s head is large and elongated.
  • Australian tree snake (Dendrelaphis punctulatus): This reptile also known as the green tree snake lives in Australia like the brown tree snake. At 5.4 feet, the green tree snake is much smaller in size than the brown tree snake.

Scientific Name

The brown tree snake is called the Boiga irregularis. Another name for this reptile is the brown cat snake. It’s called a cat snake because of its notably large eyes with vertical pupils. It’s in the Colubridae family and class Reptilia.

Population and Conservation Status

The IUCN Red List of Threatened Species describes the population of these snake as common and stable. It is reported as Least Concern.

Appearance and Description

The appearance of these snakes depends on what region it lives in. Some have light brown scales covered with a dark brown or black pattern of bands. Others are cream or tan with reddish bands. This snake’s belly is tan or cream.

They have a narrow body measuring from 3.3 to 6.6 feet long. Their narrow body structure allows them to fit between rocks, branches or even into a crevice.

This reptile is known as a cat snake because its vertical pupils are similar to a cat’s eyes. Another one of the interesting facts about brown tree snakes and cats is they are both nocturnal!

How to identify a brown tree snake:

  • Light brown scales with a pattern of dark brown bands
  • Tan or cream scales with a pattern of reddish bands
  • A cream or tan belly
  • Large eyes with vertical pupils
  • A large head compared to its slender body
A Brown Tree Snake Coiled on Branch
Brown tree snakes have tan or cream scales with a pattern of reddish bands and a cream or tan belly

Tailored Photography/

How Dangerous Are They?

These snakes are venomous, but the venom is considered mild. The fangs of this snake are in the back of its mouth and its venom is released slowly posing little danger to adults who are bitten. It’s more of a serious event if a child is bitten because of the person’s smaller size.

If an adult is bitten, it’s important to clean the wound with warm water and soap. Be sure to thoroughly dry the injured area before putting a clean bandage over it. If a child is bitten by this snake, try to keep the person calm and seek medical treatment right away. Fortunately, there’s an antivenom available to treat this snake’s bite.

Tree Snake Behavior and Humans

Because this is an arboreal snake, it usually goes unseen by people. It blends in well with the branches and leaves in its forest habitat.

They are not considered aggressive but can become agitated if they feel threatened.

These snakes are an invasive species in Guam. Shortly after World War II this snake was introduced to the island of Guam by accident. It started when one hid inside a crate in a cargo ship traveling to Guam. After arriving, the snake made its way onto the island. As time went along, their population grew. They fed on the large population of rodents and birds on Guam eventually causing the complete loss of some species. They quickly became pests on the island of Guam showing up in people’s homes in search of food.

Over the decades, Guam’s officials have taken steps to decrease the population of this invasive species of snake.

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Tree Snake FAQs (Frequently Asked Questions) 

What is a tree snake called?

There are many types of tree snakes. The brown tree snake, the blunt-headed tree snake, the green tree snake, and the paradise tree snake are some examples. All of these snakes belong to the Colubridae family.

Are tree snakes venomous?

Yes, but they’re said to have mild venom and are not dangerous to adults who are bitten. They have rear fangs with a groove in them allowing venom to slowly drip out.

How do tree snakes hunt?

Brown tree snakes are expert at pursuing their prey of lizards, bats, and birds in the branches of trees. They also hunt rats and other rodents on the ground. These snakes are nocturnal and use their sense of smell to locate their prey.

Are tree snakes aggressive?

They are sometimes aggressive when they feel threatened or trapped.

Where do tree snakes live?

They live in a forest habitat as well as in mangroves, rocky areas, grasslands, and caves.

They are found in Australia, Papa New Guinea, the Solomon Islands, and on Guam.

Though this snake’s venomous bite isn’t harmful to adults, it can be dangerous to children

They have a diet of rodents, birds, bats, and lizards.

Cat snake

Australian tree snakes also called green tree snakes, are not venomous.

Where do green tree snakes live?

Green tree snakes live in northern and eastern Australia as well as in Papua New Guinea.

When was the brown tree snake discovered?

These snakes were discovered on the island of Guam sometime between the end of World War II and 1952.

Why are brown tree snakes a problem?

The tremendous number of brown tree snakes are a problem on the island of Guam because they consume so much prey there’s little left for other species of animals. Also, they go into people’s homes, disturb domesticated animals, and can bite children.

One of the more incredible facts about this snake’s behavior is it can cling to and climb on power lines. This behavior often leads to power outages on the island!

How does the brown tree snake affect the ecosystem?

An invasive species like the brown tree snake on Guam affects the ecosystem by eating so much prey that little or none is left for other animals on the island. Plus, they’ve killed off species of birds and other mammals that used to be abundant on Guam. In addition, when rodents and birds eat seeds they redistribute them on the ground by pooping. Having fewer rodents and birds in the ecosystem means fewer seeds are dropped to replenish vegetation growing on the island.

Where is the brown tree snake invading?

The brown tree snake has invaded and continues to invade the island of Guam in the Pacific Ocean. But steps are being taken to reduce the population of this snake on Guam.

  1. The State of Queensland Department of Environment and Science, Available here:
  2. Conservation Made Simple, Available here:
  3. Thai National Parks, Available here:
  4. Wet Tropics, Available here:
  5. IUCN Red List, Available here:
  6. Back Yard Buddies, Available here:

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