Silent Island

When writing about the Lesser Short-Tailed Bat colonizing New Zealand 30 million years ago, I wrote it from the perspective of the bat. But no species can colonize an inhabited island peacefully. The bat might think of itself as a pilgrim, while the native birds consider it an invader. And as humans invade and colonize each other’s lands by caravan, ship, and airplane, a form of animal imperialism has followed us.

Guam is a South Pacific island that was, at one point, idyllic. We cannot know what the ecosystem of Guam looked like 4,000 years ago when it was first colonized by humans, but when the dust and blood settled over the millenia, those early pioneers forged a sort of peace accord with the island, and the ecosystem re-calibrated itself to accommodate them. These people became the Chamorro, a culture based on the principles of respect and reciprocity. They had a mythology, but no religion; ancestor veneration took the place of deity worship. (Although there is one 17th century account of human sacrifice.)

Then, in the 15th century, the Spanish invaded. To say nothing of the misery visited on the people, the island was invaded by the rats, pigs, dogs, chickens, deer, and water buffalo the Spaniards brought with them; an ecological blitzkrieg. When control of Guam was passed to the U.S. after the Spanish-American War of 1898, we established a major naval base there (and introduced the poisonous and insatiable cane toad), which in turn was captured by the Japanese after Pearl Harbor. The Chamorro suffered torture, beheadings, and rape under Japanese occupation, and the island suffered the Giant African Snail which devastated the island’s crops. This is not to mention all of the invasive plants and pathogens introduced, which starved the local wildlife and pushed out the native vegetation. Then, in the 1950′s, when the island was again under the stars & stripes, we struck what could be the finishing blow.

This is the Guam Micronesian Kingfisher. No picture I could find could do justice to the magnificent plumage of this bird, which I have seen at the National Zoo in Washington, D.C. It behaves very much like North America’s belted kingfisher: furtive, with a raspy, laughing call, and specialized for diving into the water to catch small fish. It was once found all over the island. Now the kingfisher, like most of the birds on Guam, is extinct in the wild, the victim of American imperialism and a little brown snake.

The reason Ireland has no snakes has nothing to do with St. Patrick. You’ll remember that waif dispersal, the means by which terrestrial animals reach distant islands, functions by three methods: flying, swimming, and rafting. Since terrestrial snakes can neither fly nor swim, they have to raft on floating vegetation. But only the smallest species tend to survive these voyages: mice, spiders, lizards, and the like. And the smaller, colder, and more distant the island, the less likely a medium-sized ectotherm will make it there. That is, before the modern boat and airplane.

Ecologists estimate that it was around 1953 when the first brown tree snakes were introduced, probably as stowaways in a cargo plane. Guam has been the transportation hub of our military operations in the Pacific since the turn of the last century, with heavy boat and plane traffic in and out of the island around the clock. The brown tree snake, a native of the Solomon Islands, couldn’t possibly have reached the distant island by natural causes. Nocturnal and secretive, its presence went unnoticed until the 1960′s, when suddenly bird populations all over the island crashed. The Guam Bridled White-Eye, an endemic subspecies, vanished. Then the Rufous Fantail. The Guam Flycatcher, the Micronesian Honeyeater, the Mariana Fruit-Dove, all gone. When the chain of extinctions, which started around the navy base on the Southern tip of the island, reached the island’s North shore, scientists finally discovered their snake problem. The tree snake specializes in capturing birds, striking from a branch above and envenomating with the fangs at the rear of its mouth. Since the snake has no natural predators on Guam, and the birds had not evolved any resistance to the species, the invader could eat to its heart’s content. It could also grow to outrageous sizes, from a standard 3-6 feet to an incredible 9 feet long. The last remaining endemic bird species, the Guam Kingfisher and the Guam Rail, were airlifted off the island and put in zoos to breed until we figure out how to kill the snakes. The kingfishers and rails that scientists couldn’t capture swiftly, and quietly, vanished.

“Quiet” is what Guam is now. It is a tropical island without birdsong. The only music in the forests of Guam at night is screaming buzz of C-3 planes above and the chirping of coqui frogs introduced from Puerto Rico. Otherwise, the silence is further muffled by the upholstery of spiderwebs that cover the trees. Without birds to eat them, the spiders flourish, draping entire trees in cobwebs and choking the forest with a silk napkin. The night is also dark. The arboreal snakes have a habit of climbing up power lines and electrocuting themselves, shorting out the power grid. The electric company, to save itself millions of dollars in damages, simply doesn’t turn the power on at night. And under the cover of darkness and silence, the snakes will often enter people’s homes, attacking pets and trying to swallow infants.

We do have a secret weapon: acetaminophen. Tylenol is poisonous to snakes. The best way yet to kill the elusive snakes is “mouse bombs“: dead mice stuffed with tylenol and attached to branch-catching streamers, which are then dropped from planes into the jungle. Additionally, the military has trained dogs to sniff out snakes at the airport, to keep them from spreading to other islands. But it may be too late. Brown tree snakes have already been sighted in Tinian, Okinawa, Hawaii, and even Texas… all American bases. The American Empire is also furthering the Empire of the Snake, an empire of silence. The problem started with the military, and we try to solve it by military means: German Shepherds and poison bombs and military airlifts for survivors. But the snake follows us, from airbase to airbase, all over the world, colonizing as we colonize. We hope to eradicate our enemies so that the Guam Kingfisher and others can reclaim their homeland. But until we stop conquering, we will always bear with us a new regime: the darkness, the silence, the slithering dread in the infant’s crib, the shroud of spiderwebs.

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About quantumbiologist

Christian Drake, AKA The Quantum Biologist, is a naturalist and poet formerly of Albuquerque, NM and currently living deep in the backwoods of the Connecticut Berkshires. He has worked in aquariums and planetariums, national parks and urban forests. When not birding or turning over rocks to find weird bugs, he enjoys rockabilly music, gourmet cooking, playing harmonica and writing dirty haiku. View all posts by quantumbiologist

14 responses to “Silent Island

  • Edward Frank

    Waif dispersal is an interesting topic. Most of the islands in the Caribbean were populated in that way. There are a couple of other considerations – not only must the animals be small to raft to the island, but they must be able to survive potential exposure to slat water. That is why there are so few amphibians on these islands. The other thing to note is that if an island is formed because a land bridge sunk, or was sheared off a piece of the mainland through tectonic motion, the initial species diversity is high. Over time it tends to go down because of the smaller area, and less diverse habitats. Eventually the diversity recovers a little as the species present on the island specialize and speciate. In waif dispersal the initial species diversity is low, and it increases over time as more species are brought to the island through the waif processes. This further increases as speciation takes place. looking at the fossil record can give you clues as to the level of initial species diversity and rate of speciation.

    • quantumbiologist

      All excellent points. I wrote a longer description of waif dispersal into my bat post, but erased it for length. True eco-geeks can look to your comment for more, and I doubt this is the last I’ll write about waif dispersal. I haven’t even covered lemurs yet…

      • The Ninja

        well in California eucalyptus trees are an invasive species – and they aren’t doing anybody any harm – in fact they help keep away bugs, cause they don’t like the smell.

  • Tatyana Brown

    Cute Carson allusion. I mean, cute for a frigging heartbreaking topic, anyhow.

    And now for the esoterica: I’ve spent a lot of time thinking about conquest and colonization vs. exploration and mutualism (within the context of human history, anyway), and while the latter is certainly possible and beneficial, it seems like it takes deliberate effort to achieve. Are there any natural examples of a foreign species being introduced to an ecosystem *without* becoming invasive/destructive? I’m wracking my brains, and I’ve got nothing.

    • Edward Frank

      To a degree whether something is destructive or invasive depends on how you define your terms. For example when the land bridge connected North America to South America around 3 million years it had dire consequences to the South American fauna. Many were driven to extinction by the North American invaders. After 3 million years however they are at equilibrium with the current environment, Have they ceased being invaders? On the North American side the continent gained opossums, armadillos and porcupines. They squeezed out a spot in the ecosystem, but did not seem to drive other species to extinction in the process. As for plants, some might argue the point, but Norway Spruce is a widely introduced tree in the northern US and it is naturalizing here. However it does not seem to be overwhelming the native trees where both are present. There is competition, and obviously a Norway Spruce is occupying space that might have been taken by a native tree species where present, but they are not taking over the forest and really seem as much at home there as do the native species.

      • Tatyana Brown

        Hey, that was fast. Your examples (both plants and animals) pretty much fit my question. I think not driving native species extinct is a main piece of what I was thinking of as “not invasive.” Can you push it further, though, and come up with an example where the non-native species is creating some kind of benefit that the ecosystem wouldn’t otherwise be accessible? For example, does the Norway Spruce create a new niche in the U.S. that native species get to take advantage of?

      • Philip T.

        Yes, it does depend on how one defines the terms being used, but I haven’t seen a definition emerge here. By most* definitions, “invasive” species is limited (and in part defined) by the movement of the species to the new environment WITH THE INFLUENCE OF MAN (e.g. accidentally, intentionally, and/or facilitated by man-made ecosystem alterations). If you stick to that definition, it’ll be much easier to discuss the topic. (And, in fact, it’s only possible to intelligently discuss it [or anything] based on a definition of the terms you’re using.) If you don’t like that definition, make one up–but state it clearly. Then a lot of ruminating about this subject will be curtailed–and further, productive discussion will be facilitated by the clarity provided by the (operational) definitions.

        *…except in some cases where native species get in people’s way of altering the environment the way they want to be altered [e.g., agriculture]

  • Edward Frank

    I will need to think about your question some more. The Norway Spruce is used by the local wildlife. They eat the seeds from the cones. They nest in its branches, They seek shelter from the winter snows under the trees shadow. I don’t know that this function is new. These functions would be served by native trees if the Norway Spruce was not there, but it is playng a useful role in the ecosystem as it exists currently. With the loss of much of teh native eastern hemlock population, and potential extinction of the species long term, because of the asian Hemlock Wooly adelgid, this spruce might fill some of the void left by the loss of the hemlock.

    • quantumbiologist

      A few more examples of immigrant species not harming the local environment:

      1) Pioneer species. Say, the first lichen and the first spider to establish on a newly-formed volcanic island, or the first aspens and locoweed after a forest fire. In fact, new species can keep piling on quite peacefully — and adding ecosystem value — until either a) an invincible new predator, such as the brown tree snake, arrives, or b) an animal that competes for a niche that is already occupied arrives. Let’s say, a new frog arrives that is very close to the old frog, both eating the same flies and competing for the same space. Competition will either drive them into separate niches (fly-eating frogs and worm-eating frogs) or kill one of the frog species off entirely. But up til then, the capacity for peaceful invasion in an ecosystem with a low total number of species exists.

      2) The invasive creature fills the niche of another creature that has disappeared. I suspect that is the case with the armadillo, a relative newcomer to North America. The niche for insectivorous burrowers might previously have been filled by a badger, but you don’t see too many badgers in Texas anymore, very likely due to human activity. Old World Horses have done quite well in North America, replacing the New World Horses that went extinct in the Pleistocene while doing little damage to the environment (when their population is managed).

      • Philip T.

        I would caution against using the term “invasive” with respect to organisms translocating WITHOUT THE INFLUENCE OF HUMANS. To do so simply muddies the already-murky waters. Again, I would suggest to create & present an operational definition of the terms being to avoid ambiguity and confusion. (If you choose to–or even if you choose not to–include native species as “invaders” even when they arrive in a place without the influence of humans, it really needs to be stated explicitly.)

  • DRD

    One potential candidate for non-destructive fauna might be the raccoon’s introduction to Germany during the 1930′s. The Germans call them “wash-bears” and cull their numbers through hunting. Left to their own devices I guess they’d be a problem for nesting birds, but the eco-niche they seem to fill at this point is the cleverly-stealing-food-from-your-cabin-or-camper niche. Which is, I guess, kind of the role they fill here in the U.S., too. Anyway, apart from a tendency toward round-worm and sometimes rabies, even some German naturalists don’t find anything terribly destructive about their presence.

  • quantumbiologist

    Yo! I don’t know if people are unintentionally turning off the “reply” button when they post comments or what, but cut it out, in the name of free dialogue.

    Phillip, I don’t know where you get the definition of “invasive species” as one that is necessarily introduced thanks to mankind, but I don’t think that’s the standard definition. Surely there are other ways for species which have a tremendous effect on a local ecosystem to disperse and establish there. Like, for example, the isthmus of Panama. You can’t blame people for North American wolves and deer traveling to South America and fucking their shit up!

    So, for the sake of a definition, let’s call an invasive species one that is non-native to a local biome, and once established there after dispersal, has adverse effects on the native species until the ecological balance adjusts to make it a necessary part of the ecosystem. Will that do?

  • Daniel

    I’m doing some research on imperialism on the island of Guam and was very interested in your article. The brown tree snake seems like it may be an important part of how the navy base has effected the people and communities of Guam.

    Are there any articles or papers that you could point me to for further information?
    Where did you get your information?

    Thank you

    • quantumbiologist

      Ooooh, someone’s asking me for citations! I’ll be the first to tell you that this blog should never, EVER be used for school papers. It… doesn’t exactly stand up to scholarly review.

      That said, I found out about the history of the brown tree snake in David Quammen’s book “The Song of the Dodo,” a truly excellent tome that I’d suggest to anyone interested in evolution and biogeography. It carries a much more in-depth, journalistic essay on the tree snake and the de-bird-ification of Guam. I highly recommend you check it out at your local library. After that… well, I find information the same way you probably do: Wikipedia and a whole lot of Google-searching. Ain’t nothing like citing a real book, but then, I ain’t in school anymore. Good luck!

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