Mistake Caused By U.S. Led to Guam’s Killer Snake Invasion: Costs Millions of Dollars Annually

By: Amanda Kusumowidagdo | Published: May 15, 2024

The United States’ occupation of the Micronesian island of Guam might have been friendlier than the Spanish invasion. The U.S., at least, managed to not eradicate the local population of the indigenous Chamorro people.

But the U.S. also brought other nightmares to the island. Even if the people of Guam can accept the capitalist invasion of fast food chains in the capital city of Hagåtña, there’s no way they can ignore this reptilian nightmare: snakes!

Brown Tree Snake Invasion

The brown tree snake, or Boiga irregularis, is Guam’s main predator these days. They’re native to other areas of the Pacific (Indonesia, Australia, New Guinea, the Solomon Islands) but not Guam. Yet, somehow, these little “brown catsnakes” made their way into the island and have since swelled in numbers.

A brown tree snake resting on a tree branch

Source: David Clode/Unsplash

These snakes don’t have any natural predators on the island, so they were able to grow in population until they filled up 212 square miles of land. And the U.S. Department of Agriculture said there are somewhere around two million of them.

Snakes on Boats and Planes

Their entry to Guam was theorized to be sometime after World War II ended. The U.S. then began importing plenty of cargo into Guam by boats and planes.

A blue and red cargo ship carrying containers at sea during daytime

Source: Ian Taylor/Unsplash

Among these cargo shipments, some insects and other animals might have been accidentally stowed on board, including the brown tree snake. Once there, instead of dying out, these snakes found a suitable habitat and thrived on the island.

Non-Native Snakes Wreaking Havoc

A brown tree snake is relatively small and doesn’t appear too threatening. But they terrorize the local lizards and birds, eating the animals and their eggs.

Black electric tower under blue sky during daytime next to a cluster of houses

Source: Leohoho/Unsplash

Another thing they terrorize: the island’s electricity. Reptile expert Thomas H. Fritts once wrote an academic paper on these snakes’ “attack” on power supplies and how they caused more than 200 power outages each year.

Snake-Caused Power Outages

According to Fritts’ studies, the Boria irregularis caused over 1,600 serious power outages in almost 20 years, between 1978 and 1997.

Person holding match stick with fire in front of candle surrounded by darkness

Source: Pixabay/Pexels

Their sheer number, climbing abilities, and penchant for disturbing the habitat all led to disruptions in the island’s electrical services and related activities.

The Economic Consequences

When a single outage affected the island and lasted for one whole working day, you can imagine there were economic consequences. And you would be correct.

A worker wearing a hard hat fixing electrical wiles on an electric pole overlooking a house yard

Source: Kelly/Pexels

One single outage could cost up to a loss of productivity worth $3 million. It also cost Guam’s economy higher than $4.5 million annually. Then, repair costs must be added in because of all the damage done to the electrical equipment.


Native Species (Almost) Extinct

A University of Colorado researcher, Haldre Rogers, pointed out how eerily silent Guam is today. This is thanks to the decimation of the native bird population by the brown tree snakes. He also brought up the case of the fruit bats’ population decline. 

Several fruit bats roosting on tree branches under the blue sky

Source: Mike’s Birds/Wikimedia Commons

Since the snakes also eat fruit bats, this species is now almost extinct in Guam. And because of the bats’ job in helping spread seeds around the island via their guano, it’s bad news for Guam’s trees and plants. “Apart from fruit bats, which are on the verge of extinction on Guam, nothing else can distribute seeds,” Rogers said.


Threatening Human Lives

Bats are not the only mammals brown tree snakes prey on. They also prey on humans, although not through their venom (it’s relatively harmless for adult humans). 

A brown snake on a wooden platform raising its head and sticking its tongue out

Source: Mark Broadhurst/Pexels

Still, when they get aggressive and attack, their bite is painful. Pets and other domestic animals are other mammals the brown tree snakes target. So, Guam’s (approximately) 170,000 citizens must also live in fear of their pets becoming a snake feast.


Taking Action Against Snakes

Guam’s authorities are dealing with these snakes in three main ways: exclusion, reduction, and extermination. Exclusion involves trying to exclude the snakes from power sources. Barriers are erected to protect electrical stations and anywhere else with a high number of animals.

A dense green forest next to a beach in Guam

Source: Philip Davis/Unsplash

Meanwhile, reduction involves reducing the snakes’ grounds to limit their movement. Special ‘habitat corridors’ are made to confine the snakes in that special area, away from crucial spots.


Extermination Is Necessary

The last measure, extermination, is unfortunate, but it’s necessary. Professionals exterminate the snakes using pesticides, poisons, and even paracetamol pastes in lethal doses for animals.

A worker wearing red suit fogging the yard

Source: Garda Pest Control Indonesia/Pexels

Killing a living being will never be easy, but considering the wreckage these snakes leave behind, this method must be employed.


Inspection and Preventative Measures

There’s no way of stopping the brown tree snakes effectively for now. They’re already there, and there’s no taking them back out.

A person wearing yellow safety jacket holding a clipboard with some papers attached

Source: RDNE Stock Project/Pexels

But at least port authorities should ramp up on inspections to make sure their population doesn’t grow even bigger. A thorough inspection of cargo shipments, at least, would help even in a small way. And thankfully, this has been carried out.


Staying Afloat

With the U.S.D.A. using pesticides on imported plants and animals, no snake should be able to slip through Guam anymore. But it might take more than that to keep the island afloat.

A beach filled with people playing on the sand and swimming in the sea

Source: Kazuo Ota/Unsplash

For an island whose 60% of total revenue comes from tourism, Guam must also depend on U.S. military spending to support its economy. So, locals must surely be hoping that the U.S. doesn’t bring another invasive species to the island.


Global Invasive Species: A Growing Concern

Invasive species, like the brown tree snake in Guam, disrupt environments worldwide, posing severe threats to biodiversity and local economies.

A lit-up globe, with Africa and South America showing in the picture.

Source: Onno Blaauw/Unsplash

These species, often introduced through human activity, adapt aggressively to new territories, outcompeting native flora and fauna.


The Rabbit Plague in Australia

Introduced in the late 18th century, European rabbits have become a major ecological disaster in Australia. Multiplying rapidly, these rabbits have led to severe vegetation loss and soil erosion, threatening native species through competition for resources.

A feral rabbit on a farm in Victoria (Australia)

Source: fir0002/Wikipedia

Control measures, including biological agents like the myxoma virus, have been implemented, yet the battle against their spread continues.


Kudzu: The Vine That Ate the South

Kudzu vine, introduced to the U.S. from Japan for erosion control, has overtaken the landscapes of the Southern United States. This invasive plant suffocates native trees and shrubs by depriving them of sunlight, dramatically altering local ecosystems.

Kudzu smothering trees in Atlanta, Georgia, US

Source: Scott Ehardt/Wikipedia

Efforts to control kudzu include mechanical removal and the use of herbicides, but eradication has proven challenging.


Asian Carp Invasion in North America

Asian carp, introduced to help keep retention ponds clean, now threaten the Great Lakes’ ecosystem. Their rapid reproduction and large size allow them to outcompete native fish for food and habitat.

Silver carp being measured

Source: Dezidor/Wikipedia

Various barriers and innovative technologies are being tested to prevent their spread into critical waterways.


Water Hyacinth: Africa’s Floating Menace

In African waterways, like Lake Victoria, the invasive water hyacinth forms dense mats, blocking waterways, reducing fish populations, and affecting local livelihoods dependent on fishing.

Haldia Municipality Pool, a public water reservoir is being choked by growing water hyacinth population as in December 2019.

Source: Invitrosantanu/Wikipedia

Efforts to remove these plants have included mechanical harvesters and biological control methods, yet they continue to be a persistent problem.


Australia’s Toxic Toad Challenge

The cane toad, introduced in Australia to control pests, now poses a greater threat than the pests themselves. Its toxic secretions harm native predators that attempt to eat it, causing declines in native species populations.

Cane Toad female, feral in the Tanamai desert, Northern Teritory, Australia

Source: Benjamint444/Wikipedia

Research into biological control and containment continues, aiming to mitigate this ecological disaster.


Caribbean’s Lionfish Problem

Lionfish, native to the Indo-Pacific but now invasive in the Caribbean, devour juvenile fish at alarming rates, destabilizing coral reef ecosystems.

Red lionfish (Pterois volitans) near Gilli Banta Island (near Komodo, Indonesia)

Source: Alexander Vasenin/Wikipedia

Diving contests and incentives for fishermen to catch them are part of the effort to control their population. Yet, their pervasive presence continues to challenge marine conservation efforts.


Economic Impact of Invasive Species

The economic impact of invasive species is massive, costing billions annually in control efforts and lost agricultural productivity.

Dozens of US $100 bills are spread out on a surface

Source: Freepik

From damaged crops to clogged water facilities, the financial burden on governments and communities is substantial. Preventative measures, though costly, are essential to mitigate these impacts.


Ecological Disruptions by Invasive Species

Invasive species cause irreversible ecological disruptions. They alter habitats, decrease biodiversity, and shift the dynamics of ecosystems.

Animals in the wild in Okavango Delta, Botswana

Source: Secret Travel Guide/Unsplash

The challenge lies in balancing control efforts with conservation, ensuring native species are protected while controlling invasive populations.


Success Stories in Eradication

Success in eradicating invasive species, like the rat eradication on South Georgia Island, offers hope.

A small white mouse looks directly into the camera in front of a pink wall

Source: Freepik

These efforts not only revive native species populations but also restore ecological balance, demonstrating that with concerted effort and international cooperation, recovery is possible.


Preventative Measures Against Future Invasions

Strengthening biosecurity measures is crucial in preventing future invasions.

A courtroom with wooden floors and walls with the American flag behind the judge’s chair

Source: Zachary Caraway/Pexels

International agreements and stringent local policies are needed to monitor and control the movement of species across borders, aiming to keep ecosystems safe from potential invasive threats.


Invasive Species Management

As the global climate changes, the resilience of invasive species poses new challenges.

Three young people reach their hands out on a globe

Source: doidam10/Canva

Innovations in genetic research and biotechnology offer potential tools for managing invasive populations more effectively, potentially turning the tide in the fight to protect native biodiversity and ecosystems.