Brown treesnakes were unintentionally brought to Guam in cargo.

IDENTIFICATION

The color of brown treesnakes 

varies from olive brown to yellow brown and shades of 

green and gray. They may 

have faint yellow and brown 

banding. The snakes have a 

broad, flat head with large yellow eyes. 

Brown treesnakes have mild 

venom which trickles down 

grooved teeth at the rear of the 

mouth. The snake kills its 

prey by injecting venom while 

holding the animal with its 

body. 

Most brown

treesnakes are 

two to three 

feet in length. In rare cases, 

adults can reach 11 feet and 

weigh about 5 pounds.

HABITAT

The brown treesnake is 

native to Indonesia, New 

Guinea, Solomon Islands and 

Northern Australia. They now 

are also found in every area on 

Guam. 

HABITS

Brown treesnakes live on the 

ground and in the trees. They 

are predators that eat birds, 

lizards, small mammals, poultry, eggs and pets. They have 

a keen sense of smell. They 

are most active at night 

(nocturnal) and are rarely seen 

during the day. Any site that 

provides protection from bright 

light and high temperatures 

may serve as a daytime retreat.

Brown treesnakes mate 

infrequently, but the females 

are able to lay fertile eggs for 

as long as six months after 

mating. She lays 4 to 12 eggs 

per clutch in caves, hollows of 

trees or other damp places 

where the eggs are protected 

from drying. She may lay two 

clutches a year. The female 

lays her eggs then abandons 

them. The young snakes 

hatch in about 90 days and are 

about 15 inches in length. The 

snakes grow to about 3 feet 

during the first year of life. 

They reproduce when they are 

about 3 years old. 

Boiga irregularis

Where in the world?

Find Guam on a globe or world 

map. What other islands are 

found in that region?

Now find the countries where the 

brown tree snake is a native 

snake. How close are these 

countries to Guam?
One of the biggest fears with 

brown treesnakes is that they 

will spread from Guam to other 

places, like Hawaii, and destroy 

native wildlife populations. 

Stopping the spread of the snake 

is a top priority. Some techniques used to prevent snakes 

from crawling into shipping areas 

include: 

• using traps around port areas 

to catch snakes

• using a spotlight at night to 

search for and capture snakes

• using dogs, like Jack Russell 

terriers, to sniff out any snake 

that may have crawled into 

cargo 

• building snake-proof fences 

around airports and docks

• removing vegetation and small 

mammals that might serve as 

habitat and prey for the snakes

• educating people in the cargo 

and transportation industry 

about the problems the snakes 

cause. 

Research currently being 

conducted at the National Wildlife Research Center in Colorado 

involves developing new ways to 

control snake populations 

including:

• possible baits and 

attractants that would make it 

easier to trap snakes

• possible biological controls 

like diseases or parasites to 

reduce snake populations

• control tools for snakes like 

toxicants, repellants and 

contraceptives.

Living in harmony . . . 

on their native island, brown 

treesnakes and 

humans live in harmony. 

• Brown treesnakes are an 

important predator of 

small mammals

• Brown treesnakes help 

control rodent and bird 

populations

Living in conflict . . .

• When introduced to a new area, 

 brown treesnakes can threaten or 

 cause the extinction of native bird 

 and mammal populations

• Brown treesnakes kill endangered or 

 threatened mammals and birds

• Brown treesnakes can bite humans

• Brown treesnakes can cause 

 electrical outages when they climb 

 electrical equipment

• In Australia, brown treesnakes 

 raid outdoor bird cages

Brown treesnakes can hold 3/4 of their body length off of the ground to reach places to climb. 
Creative Writing:

♦ Write a news story about brown treesnakes 

that gives a positive view of this animal. 

♦ Write a legend about one of the extinct bird 

species on Guam that brown treesnakes 

caused to become extinct. 

♦ Research and write a story on how to protect 

yourself when you see a snake. 

♦ Write a story about a snake and a mouse 

from the mouse’s point of view.

♦ Next write a story about a snake and a mouse 

from the snake’s point of view.

♦ Write a story about a snake invading an island where it has no predators.

Brown treesnakes have wiped out most of the 

native forest birds of Guam. Nine species of birds 

have disappeared from the island and three other 

species have been reduced to very low numbers. 

The brown treesnake has also eliminated several 

species of native lizards and is a threat to the 

native bats of Guam.

Snakes crawling on electrical lines frequently cause 

power outages and damage to electrical equipment. 

Many people seek medical treatment for snake bites 

each year with more than 80% of the snake bites occurring at night while people are asleep. In some 

parts of Guam, it is estimated there are 12,000 

brown tree snakes per square mile. 

ACROSS: 4. attractant, 6. venom, 8. threatened, 9. Jack Russell terrier, 10. clutch

DOWN: 1. native, 2. predator, 3. biological control, 7. extinction

There are many 

legends about 

snakes. Adam, Eve 

and the serpent in the 

garden of Eden is a 

well known story. The 

Aztec’s creation story 

is about “Coatilque” or 

the “Lady of the Skirt 

of Snakes.” 

Quetzalcoatl, the

Aztec Serpent God, 

was the king of the 

City of the Gods. 

According to Cherokee legend, in ancient times there lived some very 

large snakes. They had two horns on their heads 

and they had the magical power of attraction. To 

see one of these snakes was always a bad omen. 

Whoever tried to escape from one always ran toward it and was 

eaten by the 

snake. 

Japan has its 

legend of the 

serpent and the 

Sea Queen and a 

young warrior 

named Toda who 

slays the serpent 

for the queen. 

Many of these legends have given 

snakes a bad 

reputation that is undeserved. 
This activity sheet has been developed by USDA Wildlife Services. For more information about brown 

treesnakes contact your state’s Wildlife Services office or USDA Wildlife Services at 301 734-7921. 

Wildlife Activity Book and

1998 Wildlife Issue of the

Colorado Reader

Colorado Foundation for 

Agriculture 

P.O. Box 10

Livermore, CO 80536

National Biological Information 

Infrastructure

Brown Treesnake Online:

Http://www.nbii.gov/

browntreesnake

U.S. Geological Survey

Brown Treesnake Information:

Http://www.pwrc.nbs.gov/btree.

htm

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ACROSS

 4. Something that attracts animals

 6. Poison produced by some snakes

 8. The first step in the extinction of a 

species population is termed 

__________________

 9. The breed of dog used to sniff out 

brown treesnakes (3 words)

10. Group of eggs laid by snakes is 

called a _________

DOWN

 1. A plant or animal that originated in 

an area is considered _______

 2. An animal that eats another animal 

is called a _________

 3. Using disease, parasites or natural 

predators to control pest animals is 

called ____________( 2 words)

 7. When a species of plant or animal 

die outs, the result is ______