Giant Snakes That Eat Pets Are Now Roaming Free Across Puerto Rico

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The invasion of large snake species is escalating in Puerto Rico, as these formidable creatures are increasingly spotted in less traditional and harsher environments across the island. These massive predators, known for consuming livestock, pets, and native birds, have been a growing concern for over a decade.

Invasive Snakes Threaten Puerto Rico


Night had settled over Cabo Rojo’s wildlife refuge on Puerto Rico’s southwestern coast, setting the stage for an explorative hike. The ambiance was filled with the subtle sounds of insects and the occasional call of water birds. 

Biologists’ Nighttime Discovery 


Accompanied by a team of research biologists, the path through this nocturnal setting was lit by the gentle glow of flashlights, revealing the smaller inhabitants of the refuge—numerous spiders whose eyes flickered in the light.

However, the journey took a surprising turn near the rocky coastline. 

Flashlight Encounter


Caught in the beam of a flashlight, a boa constrictor, approximately 3 feet long and displaying a pattern of green, black, and yellow scales, moved quietly across the forest floor.

Snakes Invade the Puerto Rican Paradise


This sighting underscored an ongoing environmental issue: the presence of invasive snake species in Puerto Rico. Boa constrictors are now a common sight in the island’s western areas. Additionally, the central mountains are seeing an increase in reticulated pythons—some of the longest snakes globally, known for their potential to grow up to 30 feet.

Meanwhile, the spread of the ball python adds to the ecological tension, threatening local wildlife and domestic pets alike.

Over 150 Boas Captured in Months


More than 150 invasive boa constrictors have been captured in just four months—a startling figure that underscores the severity of the issue. The snakes are adapting to extremely hot, dry conditions with limited forest cover—environments that are typically inhospitable to them. 

Wildlife at Risk

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These non-native species pose a significant threat to local wildlife and pets, reflecting a pressing need for measures to manage and mitigate their impact on Puerto Rico’s diverse ecosystems.

The Escalating Snake Invasion


Local efforts to control the snake population have been ongoing, yet the situation has only intensified, with the snakes expanding their territory into larger areas. 

The absence of natural predators has led to a surge in the boa population, which has flourished unchecked over the past ten years.

Top Predators of Puerto Rican Forests


In Puerto Rico, boas and reticulated pythons hold the status of apex predators, positioned at the very top of the food chain. Their considerable appetites pose a significant threat to the local ecosystem. 

Biologist Warns of Snake Threat


Alberto R. Puente-Rolón, a biologist from the University of Puerto Rico at Mayagüez and a recognized expert on invasive snakes, underscores the severity of the situation. 

He highlights the acute risk these predators pose to the island’s bird populations, especially noted during a field trip in the Cabo Rojo wildlife refuge.

Migratory Birds at Risk


Cabo Rojo is a critical habitat within the eastern Caribbean, acting as a vital stopover for migratory and shorebird species, such as rare plovers and warblers.

These birds play essential roles in their ecosystems, controlling insect populations and dispersing nutrients across the region through their droppings.

Puerto Rico’s Biodiversity at Risk

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The threat extends beyond Cabo Rojo, impacting biodiversity across the entire island. 

Puerto Rico is home to a wealth of unique species, including dozens that are endemic, such as the Puerto Rican parrot—one of the most endangered birds globally. The interconnectedness of these species, particularly how native birds aid in seed dispersal for many trees, means that the loss of key bird species could lead to broader ecological disruption.

Saving the Endangered Puerto Rican Parrot

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The Puerto Rican Parrot was officially listed as endangered in 1967, triggering the implementation of conservation measures under the precursor to the Endangered Species Act. 

In response to the declining population, a comprehensive strategy involving captive breeding was initiated. This program aimed to stabilize and gradually increase the number of these captivating parrots, which are now further threatened by the presence of invasive snakes.

Disease Risks from Snakes


Further compounding the problem, scientists express concerns that these invasive constrictors could introduce diseases that would harm the island’s native snake populations, including the critically endangered Puerto Rican boa, found exclusively in this region. 

The presence of invasive snakes is not just a threat to individual species but poses a cascading risk to the entirety of Puerto Rico’s rich and complex ecosystems.

Lessons from Guam


Invasive snakes have wreaked havoc in various tropical locales—a stark reminder of the potential devastation they can bring. For instance, Guam witnessed nearly total decimation of its native forest bird populations due to the introduction of the venomous brown tree snake from Papua New Guinea and Australia. 

A Warning for Puerto Rico


After its arrival in the mid-20th century, 10 out of 12 native bird species were wiped out. This loss has dire implications for Guam’s forests, as many trees rely on birds for seed dispersal—a situation mirroring the ecological dependencies in Puerto Rico.

Pythons’ Toll on Florida’s Native Wildlife


In South Florida, the introduction of Burmese pythons has been linked to significant declines in native mammal populations, including rabbits and foxes, demonstrating the broad ecological impacts of these invaders.

Can Puerto Rico Curb Its Snake Crisis?


Puerto Rico’s situation (while not yet as dire) is becoming increasingly critical. 

Scientists have noted that invasive constrictors are already established in some parts of the island and are beginning to expand their reach. However, there is still a chance for local experts and environmental authorities to curb the impending ecological damage.

More Than Just Snakes

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The urgency to address this issue is compounded by broader challenges. As a U.S. territory, Puerto Rico faces financial constraints exacerbated by a history of colonialism and frequent natural disasters, which may impede rapid response efforts. 

This scenario is reminiscent of other regions like Hawaii, where delayed interventions have often meant that action is only taken when native species are nearly extinct.

A Night of Alarming Discoveries in Cabo Rojo


On an April night in the Cabo Rojo National Wildlife Refuge, located roughly three and a half hours from San Juan, the issue of invasive snakes in Puerto Rico became starkly evident. Within just three hours, three large boas were spotted—each sighting increasingly alarming. 

These snakes, larger than those usually spotted, were found wrapped around tree branches, not far from a flock of nesting shorebirds.

Hidden Predators


The proximity of these predatory snakes to vulnerable bird species like the least terns—small seabirds with distinctive black caps and smoky gray plumage—highlights the gravity of the situation. 

Last summer, researchers discovered boas in the nesting area of these seabirds, and dissections revealed these snakes had been preying on the young birds.

Human Actions Fuel Snake Crisis

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Ana Román, who oversees the Cabo Rojo refuge, articulates the concern succinctly: There is an ecological imbalance. These invasive species don’t belong here. 

The root of the problem traces back to human actions. For decades, pet traders in Puerto Rico have illegally sold constrictors and pythons, with insufficient enforcement of the laws against owning such animals without a permit. Escaped or deliberately released pets have contributed significantly to the current crisis.

Bizarre Beginnings of Puerto Rico’s Snake Problem

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There are also more unusual suspected entries of these invasive snakes into the wild. In the 1990s, an incident involving a burglary at a nearby zoo resulted in the escape of baby boas—a detail shared by a biologist who was investigating another snake at the zoo shortly after the incident. 

While this particular story lacks external verification due to the absence of contemporary news reports and the subsequent closure of the zoo, it highlights the complex and sometimes bizarre nature of how these invasive species have come to thrive in Puerto Rico.

Tracking the Snake Invasion


Researchers at the University of Puerto Rico are intensively studying the spread of invasive snakes, driven by urgent questions about their locations and the native species they most endanger. 

The initial step in these studies often involves physically capturing the snakes. During fieldwork in Cabo Rojo, for instance, biologists would use a pole equipped with a hook to securely grab an invasive boa, subsequently placing it in a pillowcase for transport.

Where Do Captured Boas End Up?


These captured snakes are primarily taken from various sources including the field, Cambalache (a holding facility managed by the Department of Natural and Environmental Resources), and directly from individuals known as reticuleros. 

Most of these snakes end up in a laboratory at the university.

Inside the Lab


Visiting this lab presents a stark and somewhat unsettling environment. 

Under the glow of fluorescent lights, several tables display euthanized snakes laid out for examination, filling the air with the combined odors of alcohol and decomposing tissue. 

What Snakes Really Eat?


In this setting, researchers, led by Colston and assisted by students, conduct dissections with surgical precision to explore the contents of the snakes’ stomachs. Their investigations primarily focus on the snakes’ diets. 

In some instances, the findings are startlingly clear, such as when a cat was discovered intact inside a boa constrictor’s stomach. 

Analyzing Snake Diets


More commonly, the analysis involves examining the snakes’ feces to determine their diet. On one occasion, an undergraduate named Mia V. Aponte Román was observed extracting feces from a snake, which, when washed and strained, revealed the claws of a green iguana, indicating the varied and sometimes surprising nature of these predators’ diets.

Local Responses to the Snake Invasion

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In Puerto Rico, the response to the invasive snake crisis varies among the local population. Some individuals take matters into their own hands by killing the massive snakes, while others opt to contact authorities who then transport these reptiles to Cambalache. 

This facility has become a daily destination for the relocation of invasive snakes, indicating the scale of the problem.

How Many Snakes Are Actually There?

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Despite these efforts, the exact number of these invasive snakes remaining in the wilds of Puerto Rico remains unknown. This uncertainty only adds to the complexity of managing the situation, as the full extent of the invasion and its impact on the island’s ecosystems is yet to be uncovered. 

Kate Smith, a self-proclaimed word nerd who relishes the power of language to inform, entertain, and inspire. Kate's passion for sharing knowledge and sparking meaningful conversations fuels her every word.