Pacific Island of Guam Faces Ecological Collapse as Millions of Snakes Take Over

Guam National Wildlife Refuge beach. Credit: Laura Beuregard / Wikimedia Commons / CC BY 2.0

Guam, a tiny land successful the occidental Pacific Ocean, has go the epicenter of 1 of the astir terrible ecological disruptions successful caller history. Once known for its vibrant forests and divers birdlife, the land is present dominated by an improbable apex predator: the brownish histrion snake.

These invasive reptiles, introduced aft World War II, person multiplied into the millions, fundamentally altering the equilibrium of Guam’s ecosystems.

In the decades since their accidental arrival, apt done subject cargo shipments, brownish histrion snakes person silently dispersed crossed the island, feeding aggressively connected birds, mammals, different reptiles, and adjacent quality nutrient scraps.

The consequences person been devastating. Today, Guam’s forests are eerily quiet, stripped of the birds that erstwhile filled the aerial with dependable and kept insect populations successful check.

Out of the 12 autochthonal vertebrate taxon erstwhile communal successful Guam’s forests, 10 person disappeared. The 2 that stay past lone successful caves and scattered municipality areas, acold from their earthy habitat. The brownish histrion snake, a nocturnal and elusive hunter, present reigns implicit this fragile environment.

Snakes devour everything, adjacent what they can’t swallow

Researchers similar Haldre Rogers, an ecologist astatine Virginia Tech who has studied the island’s ecology for implicit 2 decades, person observed the far-reaching consequences firsthand. She recalled attending a gathering connected the land wherever a roasted pig was near unattended.

When guests returned, a brownish histrion snake had wrapped itself astir the meat, tearing disconnected pieces and swallowing them whole. For Rogers, it was a startling yet acquainted reminder of the snake’s dominance connected the island.

The brownish histrion snake’s interaction connected Guam is not constricted to the extinction of birds. With fewer predators remaining, the reptiles person shifted their diets to see tiny mammals, different reptile species, and adjacent each other.

Brown histrion snake. Credit: Pavel Kirillov / Wikimedia Commons / CC BY-SA 2.0

Henry Pollock, enforcement manager of the Southern Plains Land Trust and erstwhile researcher successful Guam, said the snakes are indiscriminate eaters and person been observed consuming animals astir their ain size.

In effect to the avian collapse, a astonishing caller taxon has flourished: spiders. With their main predators gone, spider populations successful Guam person exploded. Parts of the wood person turned into web-covered landscapes.

Surveys person recovered the land hosts betwixt 508 cardinal and 733 cardinal spiders, astir 40 times much than neighboring islands specified arsenic Rota, Tinian, and Saipan. These figures lone see spiders wrong 2 meters (6.6 feet) of the ground, suggesting the existent fig is importantly higher.

A web-filled forest, live with spiders

The abundance of spiders is disposable passim the year. In opposition to the seasonal fluctuations seen connected different islands, Guam’s spider numbers stay consistently high.

Rogers described the country arsenic thing retired of a Halloween movie: dense layers of silk blanketed trees, paths, and unfastened spaces. On hikes, it’s communal for the pb idiosyncratic to transportation a instrumentality to wide webs oregon hazard being covered successful them.

The island’s forests are location to a assortment of striking spider species. Banana spiders with aureate webs, huntsman spiders arsenic ample arsenic a quality hand, and tent-web spiders that make immense communal structures known arsenic “condo webs” each thrive successful Guam’s environment.

Banana spider aureate silk orb-weaver. Credit: bansheed / Flickr / CC BY-NC-SA 2.0

Rogers noted that these condo webs tin widen from the wood level to the canopy, often lodging dozens of spiders successful a azygous structure.

These spiders, known locally successful the Chamorro connection arsenic sånye’ye’, are not the lone motion of the forest’s imbalance. The wood itself is opening to change. With birds gone, galore autochthonal trees are struggling to reproduce.

Around 70 percent of Guam’s autochthonal trees trust connected birds to disperse their seeds. Now, fruits autumn to the crushed and rot, oregon seeds neglect to germinate owed to a deficiency of dispersal oregon mediocre increasing conditions nether genitor trees.

The soundless illness of Guam’s forests

This disruption has slowed wood regeneration. In a steadfast system, fallen trees make gaps that caller plants rapidly fill. On Guam, these gaps often stay empty. Rogers compared it to tearing down a gathering successful a city, typically premier existent estate, but present near untouched owed to the lack of seed-dispersing birds.

The brownish histrion snake’s predatory behaviour has go adjacent much disturbing. In a caller survey adjacent Andersen Air Force Base, Rogers and her squad tracked young Såli, a wood starling taxon that inactive survives successful tiny numbers.

Using vigor transmitters, the squad discovered galore of the devices wrong snake stomachs. But adjacent much unsettling were fledglings recovered dead, coated successful snake saliva, but uneaten. In astir fractional of the cases, the birds were excessively ample to swallow. The snakes killed them anyhow and moved on.

The brownish histrion snake is not lone ruthless but besides highly adaptive. To support the remaining Såli, conservationists placed nest boxes connected gangly metallic poles with slippery surfaces, believed to beryllium unclimbable.

But successful 2021, Julie Savidge, a prof astatine Colorado State University, and her squad documented an wholly caller behavior: lasso climbing. The snakes were capable to wrapper themselves astir the poles, looping their tails and inching upward, mimicking the question of climbing a coconut tree.

Snake power is costly and often ineffective

Despite decades of power efforts, Guam’s brownish histrion snake colonisation continues to grow. Authorities person tried astir each method: ocular surveys, traps, chemic repellents, toxic baits, and adjacent probe into imaginable viruses that could people the taxon without harming others.

This attack is akin to the arguable usage of myxomatosis successful rabbits, which caused wide suffering and raised ethical concerns.

The U.S. authorities presently spends astir $3.8 cardinal annually connected snake power successful Guam. But occurrence has been limited. One of the fewer effectual strategies has been implemented astatine Andersen Air Force Base.

There, snakes were baited with acetaminophen, communal successful over-the-counter symptom relievers but lethal to brownish histrion snakes. Just 80 milligrams, a fraction of a modular tablet for humans, is capable to termination adjacent ample individuals.

To forestall reinvasion, the country was surrounded by a snake-proof fence. Inside this protected zone, snake numbers person dropped significantly. But replicating this occurrence crossed the island’s rugged terrain is considered unfeasible by astir scientists.

A aboriginal held hostage by a predator

As the wood continues to suffer its birds, the semipermanent consequences stay uncertain. Many histrion taxon are already declining, and the structural integrity of the wood is weakening. Without intervention, the harm whitethorn beryllium irreversible soon.

For now, Guam remains an land softly ruled by snakes; stealthy, persistent, and astir intolerable to control.

The spiders that present broad its forests are lone the astir disposable motion of a deeper ecological collapse, 1 that whitethorn instrumentality generations to repair; if repair is adjacent possible.