How the Brown Tree Snake Wreaked Havoc on Guam's Birds

The brown tree snake is a slender, medium-sized snake that typically grows between 3 and 6 feet (0.9 to 1.8 meters) long, though some individuals can reach lengths of up to 10 feet (3 meters).

Their skin is usually a reddish-brown to yellowish-brown color, with darker crossbands running along their bodies. This coloring helps them blend in with tree bark and forest floors in their native habitats.

Despite their slim build, brown tree snakes are skilled climbers. Their long, slender bodies allow them to wrap around tree branches with ease, which helps them hunt for prey in treetops and even inside buildings when they invade human habitats.

Lastly, brown tree snakes are mildly venomous. While their bite isn't deadly to humans, it can cause swelling and pain. Their fangs are located toward the back of their mouth, so they're more of a threat to smaller animals like birds and mammals.

Interestingly, the brown tree snake doesn't have recognized subspecies, but there are slight regional variations based on its native range. These snakes are naturally found in Northern Australia, Papua New Guinea and the Solomon Islands.

The coloration and size of the brown tree snakes can vary depending on where they’re found. In some regions, for instance, individuals tend to be smaller and have more prominent crossbands.

In the areas where brown tree snakes have been accidentally introduced — like Guam and other Pacific islands — their population has adapted well to the local environments, sometimes outcompeting native species for resources.

This adaptability has made the snake a major problem in places where it isn't supposed to be.

Brown tree snakes are nocturnal hunters, meaning they're most active at night when they slither through forests and urban areas in search of prey.

These snakes are typically solitary, only coming together during the mating season. When brown tree snakes invaded human habitats on Guam, their nocturnal behavior helped them avoid detection for years, allowing their population to grow without much control.

Although they spend much of their time alone, brown tree snakes can sometimes be seen in large numbers where food is abundant, particularly near bird nesting sites.

They're not territorial, but they will defend themselves if threatened. If you come across one, it’s more likely to retreat than strike unless cornered.

One of the key reasons brown tree snakes have become such a major problem is their diet. In their native range, they prey on small mammals, reptiles and bird eggs.

However, in Guam, they've decimated the island's bird species, including many of Guam's native forest birds. Brown tree snakes are excellent climbers, and they have a particular fondness for bird eggs, which has led to the near extinction of several bird species on the island.

These snakes also eat small mammals, but it's their impact on bird populations that’s been most devastating. Without natural predators in Guam, there hasn't been an effective way to control snake populations, leading to the near-total collapse of some native forest vertebrate species.

In their native habitats of Northern Australia, the Solomon Islands and Papua New Guinea, brown tree snakes thrive in forests, mangroves and even grasslands. They’re excellent at blending into their surroundings and are most often found climbing trees in search of prey.

But when brown tree snakes were accidentally introduced to Guam, they quickly adapted to the island's ecosystem, including invading human habitats.

On Guam, these snakes can be found just about anywhere — on power lines, in attics and in dense forested areas. (The species loves a cool and dark location.) They’ve even caused frequent power outages by climbing electrical equipment.

The lack of natural predators and the abundance of prey species have allowed the brown tree snake population to explode, making it one of the most infamous invasive species in modern history.

The reproductive cycle of brown tree snakes follows a pattern typical of many reptiles. Females lay clutches of four to 12 eggs, usually in hidden, sheltered places like rock crevices or inside hollow trees.

The eggs hatch after about 60 days, and the young snakes are fully independent from birth. These juveniles grow quickly and reach maturity within two years.

In Guam, without natural predators to keep them in check, brown tree snake populations have been able to reproduce rapidly. This unchecked growth has contributed to the ecological disaster on the island, with native species suffering as a result.

In their native range, brown tree snakes are not considered endangered or at risk. However, as an invasive species, they've created a huge problem.

The National Wildlife Research Center, along with other agencies, has been working to control the brown tree snake population on Guam by developing new ways to capture or kill the snakes, including traps and toxic bait.

Conservationists are also focusing on protecting Guam's remaining bird species by isolating and breeding them in snake-free areas. However, these efforts are an ongoing challenge due to the widespread presence of brown tree snakes on the island.

While the snakes themselves aren't endangered, their impact on ecosystems where they've been accidentally introduced highlights the delicate balance between species and their environments.

We created this article in conjunction with AI technology, then made sure it was edited and fact-checked by a HowStuffWorks editor.