The Brown Tree Snake is a species of arboreal snake that is native to parts of Australia, New Guinea and Indonesia.
This species is also called the Brown Cat Snake and despite being a colubrid snake, it is rear-fanged venomous.
This snake was introduced to Guam in the mid-1900’s and has established itself as a very problematic invasive species. It has even wiped out some of the other species on the island.
Brown Tree Snake Taxonomy
In the Animal Kingdom, Taxonomy is used as the science and practice of classifying different species and sub-species based on their biological and genetic makeup.
Family
The Brown Tree Snake belongs to the Colubridae or Colubrid family of snakes. This is the largest family of Snakes in the world consisting of many popular species such as Pine Snakes and Milk Snakes.
With around 250 different genera of Colubrids, these snakes can be found on every continent except Antarctica which also makes them the most widely distributed family of snake in the world.
The vast majority of Colubrid snakes are non-venomous, or at least contain a venom that isn’t considered to be medically significant to humans.
However, there are a number of species of Colubrid snakes that contain venom capable of killing humans. This includes species from the Boiga and Rhabdophis genera as well as other snakes such as the Boomslang.
Genus
The genus that the Brown Tree Snake belongs to is the Boiga genus. This is one of the genera that contains snakes that have medically significant venom.
The species in the Boiga genus are commonly known as Cat Snakes or Cat Eyed Snakes. There are currently 38 recognised species in the genus.
Some of the Common species in the Boiga genus include the Mangrove Snake, the Green Cat Snake and the Dog-Toothed Cat Snake.
Species
The scientific name for the Brown Tree Snake is Boiga irregularis and there are currently no recognised sub-species.
The species was first described in 1802 by a German herpetologist named Blasius Merrem.
Merrem was also responsible for describing other species such as the Cuban Knight Anole.
Brown Tree Snake Description
The Brown Tree Snake is a large species in terms of length as they can grow to over two metres in length.
However, they are a very slender snake that is laterally compressed. They also have very long tails.
They are light brown in color and can have a uniform coloration throughout. Some specimens have darker markings along the back of the snake.
While the most common background color on these snakes is light brown, it can vary with some snakes being red, yellow or even an off-white coloration.
They have a typical Cat Snake appearance with their large head and bulging eyes. They also have fangs in the back of their mouth, making them a rear fanged snake.
Natural Habitat and Distribution
The Brown Tree Snake is native to parts of Australia, New Guinea and Indonesia but has also been introduced to other parts of the world.
In Australia, they can be found along the Northern and Eastern Coasts of the country.
Their range extends from the Kimberley region of the Western Territory, right across the Coast of the Northern Territory and into Queensland.
Their range then extends along the Northern and Eastern Coasts of Queensland down into New South Wales where they can be found as far South as Sydney.
On the island of New Guinea, the Brown Tree Snake can be found on both sides of the island, in Papua New Guinea and the Indonesian territory of Papau.
It can also be found on many of the other islands in the Eastern part of Indonesia including Sulawesi and Maluku.
The Brown Tree Snake was introduced to Guam sometime around the 1950s and has established itself on the Pacific Island as an extremely menacing invasive species.
It is believed that the snake was introduced on shipments to the island and as Guam is an important shipping route, it is feared that the snake could branch out to other islands on more shipments.
There have been isolated reports of these snakes found in other places also but it is not believed that breeding populations have been established.
One area of concern is the Mariana Islands, particularly Saipan where a number of individuals have been found.
The number of specimens found has led researchers to believe that breeding populations have been established but this is yet to be conclusively confirmed.
The Brown Tree Snake likes to live in a variety of different habitats from lowland woodlands and coastal forests to the rainforest of New Guinea. It can also be found in savannas and mangroves.
They can also be found in caves and have made use of human settlements, living in attics, on cropland and even in poultry barns.
Brown Tree Snake Behaviour
The Brown Tree Snake is a nocturnal species, meaning they are mainly active during the night and will spend most of the day sleeping or resting.
They have large bulging eyes with slit pupils which helps the snake to see well when it is dark.
During the day, this snake will rest in just about anywhere they can find shelter such as trees, rock crevices, caves, hollow logs or inside man-made structures.
They are an arboreal species that is perfectly adapted to life off the ground. They have a long, slender and laterally compressed body which helps them move through the branches of trees.
Brown Tree Snake Venom
The Brown Tree Snake has venom glands in the back of its mouth. These types of snakes are often referred to as ‘Rear Fanged Venomous’ species.
The delivery system of this venom isn’t very efficient and they can’t inject as much venom as other venomous snakes such as Vipers.
The venom is mildly neurotoxic and may also contain cytotoxins. However, because of the poor delivery system and weak nature of the venom, it is not considered dangerous to adult humans.
The Brown Tree Snake is believed to use its venom to subdue lizards which it can fit in its mouth and ‘chew on’ to inject its venom.
While generally not considered dangerous to an adult human, if a young child is bit by a Brown Tree Snake it should be considered a medical emergency because of their lower body mass.