An Ark With No Ararat

"We aren't arks, we're life rafts... with very limited seating."

-C. Peeling

"Should we not then ask ourselves whether some species, which have now become rare, and for the conservation of which cultural and scientific zoological gardens are making the greatest sacrifices with little marked success, are not doomed to disappear and whether man's interference in these cases is fully justified"

- Walter Van den bergh, Breeding the Congo Peacock at the Royal Zoological Society of Antwerp

Zoos love the analogy of the Ark.  Sometimes, I think they're downright obsessed with it.  Glancing at my bookshelf, I can read the titles - The Modern Ark, The Overloaded Ark, The Stationary Ark, The Ark in the Park (two books - one a history of the Lincoln Park Zoo, the other of the Zoological Society of London), Ethics on the Ark, and, of course, Sailing with Noah.  There is the Amphibian Ark, devoted to the conservation of endangered amphibians, and ARKS is a record-keeping software used at many facilities.

The importance of the Ark has changed over time.  Initially, it represented what every zoo director craved above all else - a pair of everything, two of each animal in neatly organized displays, hopefully bearing offspring.  In this age of human-induced mass extinction, however, the Ark has taken on new meaning.  With habitat loss, over-exploitation, introduced species, and now the specter of global climate change, more and more species are finding survival in the wild to be impossible.

Some have already been declared Extinct the Wild, the category that the IUCN has placed between Extinct and Critically Endangered.  It means that there are specimens in zoos, aquariums, botanical gardens, seed banks, or private collections, but none living out in  nature.  Species in this listing include the Guam rail and the Micronesian kingfisher, as well as the golden sifaka and the Alagoas curassow; the black softshell turtle is known from a single pool in a temple in Bangladesh.  More species are likely to join this list in the near future.  Lately, the dream has been to breed zoo animals in captivity, safe and secure until the magic day comes when we can reintroduce animals back into the wild.  But what if that day never comes?  What if the Ark is a ride that no one ever gets off of?

Being a conservation biologist is sort of like being a combat medic on a battlefield - there often is an element of triage involved.  Some species will do fine no matter what we do, some we probably can't save no matter what we do.  The question is, do the extinct in the wild species fall into this last category?

Some people would say "yes," including a decent number of animal rights' activists that I've spoken to.  To them, what is the purpose of keeping an species alive if it will only survive behind fences or safety glass in captivity?  Better, in their minds, to devote that money, those resources to other species that are still fighting for survival in the wild (such as it is).

The thing is, though, that some species have come back from extinction in the wild.  At least three species on the IUCN list - the scimitar-horned oryx, the Kihansi spray toad, and the Socorro dove - are being reintroduced at this time.  None of this would have been possible if we'd written off the captive populations and pulled the plug on them.  Same with previously extinct in the wild species, such as the red wolf, black-footed ferret, and California condor.  They only survive in the wild now because they survived in zoos earlier.  These species have all been reintroduced into the wild... of course, it helps that, for them, there was still a wild to be reintroduced into.  What if there wasn't?

Consider the birds of the Mariana Islands.  If efforts to relocate Guam birds on other islands failed (to be clear, we're in the hypothetical now - so far, the MAC program seems to be working), and the Guam rail and the Micronesian kingfisher would survive only in zoos and other breeding facilities like SCBI, should they still be saved?  Or should we give up?

My vote is an emphatic NO.  Just because we can't do anything to help the species now doesn't mean we won't be able to later on.  Maybe someday we'll find a way to remove the brown tree snake from Guam.  Maybe we'll find more islands that are better suited.  Maybe birds somehow find a way to adapt to life on Guam.  MAYBE we'd think of something.  As long as a species survives, we have options.  Once it goes extinct - not extinct in the wild, but extinct for real - we have none.*

*Unless we're going to go all Jurassic Park and start cloning... but I see that being quite some way down the road...

Satire: The Simpsons (Bart the Mother)

The great thing about The Simpsons is that there is a clip or a quote for just about anything you can imagine (I mean, it has been running since the beginning of time, so it's not like it hasn't had plenty of opportunities).  Even the brown tree snake gets parodied, albeit it reimagined as the fictitious Bolivian tree lizard (why the change - were they worried that the snakes' lawyers would sue?) - a vicious egg-eater with a penchant for eating the eggs of birds with naughty-sounding names.

Species Fact Profile: Brown Tree Snake (Boiga irregularis)

Brown Tree Snake

Boiga irregularis (Merrem, 1802)

Range: Northern Australia, New Guinea, Indonesia, Solomon Islands, Guam (Introduced)
Habitat: Tropical Forest
Diet: Frogs, Lizards, Birds, Eggs, Bats
Social Grouping: Asocial (will share refuges)
Lifespan: 13 Years (Captivity)
Reproduction: May breed year round in wetter portions of range, females have sperm storage abilities, 4-12 eggs deposited in hollow logs, rock crevice, or other hiding place; they hatch between 76-90 days later.  The age of sexual maturity depends on body length
Conservation Status: Not Listed

• Body length varies across range, but snakes from the introduced population of Guam achieve the greatest length at over 3 meters.  The snake is long and slender with a proportionately large head
• Wide range of color morphs, including the namesake brown-yellow, as well as blue-and-white or red-and-white banding
• Most active by night, the snakes have large eyes with elliptical vertical pupils, sometimes giving them the nickname of "cat snakes"; daytime hours are often spent inactive under rocks, in crevices, or in dense vegetation
• Primarily arboreal, but also known to forage on the ground or enter grasslands or clearings while crossing from one patch of habitat to another
• Species is mildly venomous (the venom is neurotoxic), with two small, grooved fangs located at the rear of the mouth.  Snakes that are threatened will rear up in a threatening position, but bites on humans are uncommon
• The brown tree snake was first detected in Guam in the 1950's, presumably accidentally imported in military cargo during World War II.  Since then, the snake has wrecked havoc on the predator-naive native bird-life, driving many Guam species to extinction or extirpation

Marianas Avifauna Conservation

On Guam, the damage has been done.  The accidental introduction of the brown tree snake to the island has resulted in the extinction or extirpation of many of the island's bird species, the severe decline of many others.  Efforts to reduce the numbers of the snake are in place, but the main focus since has been to limit the spread of the snake.  The realization has been that what has happened on Guam could happen elsewhere.

But what do to about the survivors?  The Guam rail, the Micronesian kingfisher, and other birds which now survive in zoos and breeding centers - what about them?  Maintain them in captivity forever, and if so, to what end?  Reintroduce them to Guam?  You might as well pluck them first so the snakes will have an easier time swallowing them.  Recently, a consortium of government agencies, NGOs, and zoos has come up with another option - the Marianas Avifauna Conservation Project.

The premise of the MAC project is simple.  There are lots of islands in the Marianas, many of which tend to be similar in most respects - plant life, insect life, climate.  Not all have the same species of birds.  Most importantly, not all have the brown tree snake.  The decision was made to transport birds - either wild survivors, captured and relocated, or captive-bred individuals - to snake-free islands, islands where they might have not been present originally, but where they can survive in a wild state.

At first glance, the idea seems counter-intuitive.  It was introducing an alien species (albeit, not on purpose) which led to this mess in the first place.  What if fifty years from now we're watching some Micronesian lizard species being wiped out by invading kingfishers?  No one can be positive what will happen, but the scientists involved very thoroughly took a census of each candidate island and its flora and fauna.  They came to the conclusion that it would likely work out, and decided it was worth the risk.

The partnership requires the participation of many players.  Government agencies have the authority to allow the transfers.  Local peoples have the knowledge about the landscape and the presence or absence of birds or snakes.  Zoos have the expertise for breeding the birds in captivity, or maintaining birds that are temporarily held captive as they are moved from island to island.  Together, they are accomplishing the nearly-impossible task of restoring some of these species to the Marianas, some for the first time in decades.

Marianas Avifauna Conservation Plan

It's not that Guam itself is being written off as doomed - they fight to control the numbers of the tree snake continues.  Still, the sooner members of the affected species are back in the wild living under natural conditions, the brighter their future will be.

From the News: NMI students learn about nature's treasures

NMI students learn about nature's treasures

One of the major problems with invasive species, habitat loss, and other environmental problems is that it leads to a creeping norm.  Consider the Mariana Islands, where for decades the brown tree snake has reigned supreme, while many of the once plentiful endemic island birds have vanished.  To the children growing up on Guam, the brown tree snake must seem to be the native; in the wonderful event that the Guam rail and other island birds were ever successfully reintroduced, it is they who would seem the aliens.  Likewise for habitat loss - if every generation grows up with a more degraded environment than their parents knew, pretty soon the standard of what is considered a normal, pristine environment is lowered as well.

It's exciting to see that children in the Northern Marianas are being given the chance to explore and study the biodiversity that (still) surrounds them.  Only by teaching the next generation to understand and value the natural world around them can we hope to ensure that they will step up to become its next generation of protectors.

Students examine the skeleton of a whale (from Marianas Variety)

Sporcle Quiz: Birds of Guam

This month, we met three bird species - the Guam rail, the Mariana fruit dove, and the Micronesian kingfisher - which suffered as a result of the introduction of the brown tree snake to Guam.  these three weren't the snake's only victims, however.  this month's quiz shows how the bird-life of Guam was impacted by the snake's arrival on the island.

Birds of Guam

Species Fact Profile: Micronesian Kingfisher (Todiramphus cinnamomina)

Micronesian Kingfisher

Todiramphus cinnamomina (Swainson, 1821)

Range: Micronesia, Palau

Habitat: Forests, Woodlands, Mangrove Swamps

Diet: Insects, Lizards, Crustaceans

Social Grouping: Solitary or Paired

Lifespan: 10-12 Years, Maximum 20 (Captivity)

Reproduction: Both parents build the nest (usually in a tree cavity or termite nests), nesting season is December through July. Two eggs are incubated for 23 days. chicks are fed by both adults and fledge at 40 days.  Sexual maturity is reached at 3 years

Conservation Status: IUCN Extinct in the Wild (Guam subspecies)

• Body length 20-24 centimeters, weigh 55-85 grams
• Cinnamon brown plumage with a blue tail and metallic green-blue wings; males and females look alike,  except for the paler breast feathers in the female
• The kingfisher makes its first morning call at (almost) the same time every morning, so regularly that local people used it to tell time
• Often hunt from tree branches and other exposed perches, swooping down when they sight prey; prey is seized and then beaten against tree branches to kill it and (in vertebrate prey) break bones
• Thee subspecies - the nominate, from Guam, is the largest; the other two are T. c. reichenbachii (from Pohnpei) and T. c. pelewensis (the smallest, from Palau).  The now-extinct Ryukyu kingfisher (known from a single specimen) may also have been a subspecies of Micronesian kingfisher.  The living subspecies are sometimes described as separate species
• The Guam subspecies was driven to extinction in the wild following the introduction of the brown tree snake to the island; the last 29 birds in the wild were captured for captive breeding in the 1980's, and the species had vanished in the wild by 1988

A World of Weeds

"It is our decision, ours today, whether Earth continues to be a marvelously living, diverse oasis in the blackness of space, or whether the 'charismatic megafauna' of the future will consist of Norway rats and cockroaches."

- Dave Foreman, Confessions of an Eco-Warrior

In the first chapter of his book Sailing with Noah, Saint Louis Zoo President Jeffrey Bonner stands outside of his office, watching drama unfolding at his bird feeder.  House sparrows, starlings, and rock doves (pigeons) bickered and squabbled, with one unfortunate sparrow getting the worst end of the deal.  Bonner was mulling his options, deciding whether or not to intervene.  However, "before I could move, I had a... thought.  Not a single one of those birds were supposed to be there in the first place.  All three species - house sparrows, starlings, and pigeons - are interlopers."

If the brown tree snake's spread across the islands of the Pacific could be likened to a blitzkreig raid, then the pigeon, starling, and sparrow would be more like a march of world domination.  From their native lands they have now spread across the globe in the wake of human activity... and they haven't traveled alone.  Besides our domestic animals (many of which have gone feral in new lands), a host of other animals have followed humans across the world and established themselves around the globe.

If European birds have invaded North America, then at least the North Americans can take comfort in knowing that gray squirrels and Canada geese have invaded Europe.  Brown rats, cane toads, raccoons... these animals belong to a select group of species which I call the "wildlife weeds."

Weed wildlife, like weed plants, are tough, adaptable, and tend to be generalists.  Some are invasive to the areas where they are found now, some have been native, but have changed their behavior dramatically.  They breed readily and thrive in a variety of habitats.  Most importantly, they do not seem troubled by the presence of humans, and many have adapted to take advantage of humans as a provider of habitat and food.  As a result, they tend to out-compete more sensitive species, eventually supplanting them.

There's a beautiful creek in the park near by home, one where I go bird-watching on my days off.  Incredibly, despite its seeming perfection for waterfowl, I almost always see only two species - Canada geese and mallards.  On the rare occasions when I do see something else, the bird in question usually takes off in a panic as soon as it notices me, even if I'm far away.  Mallards and geese are comfortable around people - they don't waste energy flying away from me, and some even approach me looking for food (doubtlessly spoiled by picnickers elsewhere in the park).   For many island birds, a lack of fear of man proved disastrous to their survival.  For many weed species, lack of fear of man (or at least general indifference) is a winning strategy.

I'm afraid that we may be moving towards a world where most species are either extinct or found only in the last remnants of wild habitat away from humans.  Instead, the world will be filled with a cadre of weed species, which will be the same all over the planet.  It won't matter if you are in New York, Nairobi, or New Delhi, the animals in the park, the birds in the trees, will all be the same.

We'll have created new, blended, simplified ecosystems, far less unique and magical than the ones that used to exist.  And the world will be a much drabber, sadder place.

Zoo Review: Smithsonian Conservation Biology Institute

When William T. Hornaday first began to image the institution that was to become the Smithsonian National Zoological Park, he had something special in mind.  Rather than making a copy of the zoos that were cropping up across Europe, he envisioned a different kind of facility, one that would help him satisfy his ambition of saving - through captive breeding - the vanishing wildlife of North America, the American bison in particular.  Essentially, he envisioned the Smithsonian Conservation Biology Institute.

The only problem was, he was about one hundred years too early.

Founded in 1974, SCBI (formerly known as CRC - Conservation and Research Center) is tucked away in the farmlands of Front Royal, about an hour west of Washington DC.  Unlike its more famous sister institution in the nation's capital, it is closed to the public, only open during certain open houses and special events.  Prior to being owned by the Smithsonian, it was used by the US Army to supply horses and mules for military use.  Now, it is a breeding center for some of the most endangered species on earth, especially those which need some space and are too shy or delicate to breed easily in an urban zoo setting.  Among the species represented here include three species of crane (hooded, red-crowned, and white-naped), as well as brown kiwis, Mongolian wild horses, scimitar-horned oryxes, clouded leopards, and maned wolves.  Many of the black-footed ferrets being reintroduced into the wild start their lives in Front Royal.

Among the endangered species being worked with at SCBI are birds of the Mariana Islands, such as Micronesian kingfishers.  With highly endangered species, such breeding facilities - allowing multiple members of a species to be housed together, rather than a pair as is the case at many zoos - have a major advantage.  By housing lots of animals together in facilities designed specifically for breeding purposes, animals can easily be moved and re-paired until an ideal breeding arrangement is found.  For that reason, many of the nation's most genetically valuable "problem cranes" are sent to SCBI for breeding.

In 2001, Secretary of the Smithsonian Lawrence Small announced that the facility would be closed, part of his plan to refocus the Smithsonian around those features which were most profitable and attracted the most visitors - after deafening outcry, he backed away from the plan.  Still, it seems that the Smithsonian is now looking at SCBI with the philosophy of "use it or lose it", and it seems like the facility has been expanding rapidly since then (when I made my first and only visit, a new facility was under construction for breeding cheetahs).

The most impressive change, however, has probably been the new partnership with George Mason University to established a PhD program in conservation biology, where students learn the latest methods and philosophies of the field.  Such an integrated approach between zoo and field biology is essential to the future survival of many species.  It is developments like this that show that SCBI - while unsung and unrecognized by many people outside of the zoo community - is an important leader in the fight to save biodiversity.  If you get a chance to attend an open-house, do so.  You won't see a huge variety of animals, or a lot of beautiful exhibits.  You will, however, get a new insight into how some of our rarest species are being saved from extinction.

Species Fact Profile: Mariana Fruit Dove (Ptilinopus roseicapilla)

Mariana Fruit Dove

Ptilinopus roseicapilla (Lesson, 1831)

Range: Mariana Islands (Extirpated on Guam)
Habitat: Limestone Forests, Secondary Growth
Diet: Fruits
Social Grouping: Solitary or Paired (Not Territorial)
Lifespan: 20 Years (Captivity)
Reproduction: Breed year round (peak breeding season April - August), nest on flimsy stick platforms in the forks of trees, usually lay a single egg which is incubated for 17-18 days, chick fledges at 14-18 days
Conservation Status: IUCN Endangered

• Body length 22-24 centimeters, weight 93 grams
• Males and females look alike - predominately green, with the top of the head is a deep, rose-red cap with a grey head, back, and breast; the stomach has a yellow patch, with additional yellow under the tail coverts; juveniles are completely green
• Very arboreal, the doves primarily stay in the canopies of the trees, but may come to the ground to feed, including on invasive plant species
• The species was last seen on Guam in 1985, extirpated following the introduction of the brown tree snake; it does, however, exist in the wild on other islands in the Marianas, as well as in North American zoos and aviaries
• Official bird of the Mariana Islands

Book Review: Out of Eden: An Odyssey of Ecological Invasion

"The invaders are legion: escaped pets; sports fish and garden plants run amok; bugs that came hidden in the foliage of introduced garden plants; pests that were introduced to control other pests, with greater or, usually, lesser success... the invaders are from anywhere, going everywhere."

The brown tree snake dominates the cover of Alan Burdick's Out of Eden: An Odyssey of Ecological Invasion, sprawling across the front, its tail wrapped around the back.  That's fair enough.  The story of the snake's conquest of Guam takes up the first fifth of the book, making it the poster child for invasives (this book has been one of my main sources for this month's Mariana theme). Eventually leaving Guam, the author takes the reader island hopping around the world, from Tasmania to Hawaii to the inverse-of-an-island, the Great Lakes.  All the while, he tracks the invasive species which are wreaking ecological havoc, as well as encountering the biologists who are trying to control them.

Out of Eden is about invasive species, but it's also about the people who unwittingly (and sometimes deliberately) spread them around the world.  Humans are the ultimate dispersal system, and Burdick examines in detail how we move animals around the world.  The brown tree snake hitches rides on planes.  Barnacles, green crabs, and other marine invaders travel in ballast water.  An experiment to recreate how canoeists populated the islands of the South Pacific also proved to be an experiment in invasion biology, as the canoes were quickly filled with stowaways (including a particularly obnoxious gnat species).  Burdick even tours a NASA facility to consider how humans could potentially transfer life around the cosmos... or bring an alien invasive back to earth.

The book raises interesting questions about what it means to be an invasive.  Pigs have run feral on the Hawaiian islands for over a thousand years, and have an integral role in Hawaiian culture. Their impact on native ecosystems has been very negative, but native Hawaiians scoff at efforts to eradicate them.  They belong here, they say - might as well try to eradicate us.  How long does it take for an invasive to become a native?  Similarly, what would happen if the brown tree snake had reached Guam not in an airplane wheel well, but on a floating raft of vegetation, reaching the island without human assistance.  Would that invasion have been natural?  In that case, should we have stood by as the snake ate its way through the island's avifauna?

Zoos receive scant notice in the book.  Burdick mentions that some Guam birds - the Guam rail and the Micronesian kingfisher - were saved in zoos.  He also mentions that zoos will sometimes accept confiscated animals intercepted at customs.  One aspect which is not considered is zoos as a source of invasive species through escapes.  It's an unlikely occurrence, but one that many government agencies take seriously, hence the stringent regulations on which zoos are allowed to house some potentially invasive species.

Most importantly, Out of Eden challenges the role of humans in a natural system.  Are we - and our brains, our behavior, our traveling - part of nature, and the consequences of our actions part of that natural system?  Or do we have an obligation to correct our introductions, accidental or otherwise?

Out of Eden: An Odyssey of Ecological Invasion at Amazon.com

From the News: USDA dogs sniff out snakes

USDA dogs sniff out snakes

Striker, a U.S. Department of Agriculture brown tree snake detector dog, scratches at a cargo load notifying his handler that he has found a snake during a daily training session April 30, 2015, at Andersen Air Force Base, Guam. All USDA snake detector dogs are acquired from various rescue shelters in the Atlanta area and are selected based on temperament, willingness to work, motivation and prey drive. (U.S. Air Force photo/Senior Airman Katrina M. Brisbin)

Following the brown tree snake's invasion of Guam, the conservation reaction to the snake has been two-fold.  Firstly, biologists are trying to remove the snake from Guam (or at least get it to a more manageable level) so that bird life can again be reestablished.  Secondly, priority is being given to limiting the spread of snake so that it doesn't expand its range into more islands, inflicting more damage.

Both methods are reliant to some degree on finding the snakes, which isn't easy - they are masters at hiding.  Sometimes, you just need a little help from man's best friend...

Species Fact Profile: Guam Rail (Gallirallus owstoni)

Guam Rail

Gallirallus owstoni (Walter Rothschild, 1895)

Range: Previously Guam, now Rota (Reintroduced)
Habitat: Secondary Growth, Mixed Forest
Diet: Gastropods, Lizards, Insects, Seeds, Palm Leaves
Social Grouping: Territorial Pairs
Lifespan: 10 Years (Captivity)
Reproduction: Breed year-round, lay 2-4 eggs in a shallow nest of leaves and grasses on the ground; both parents share incubation and chick-rearing duties; chicks leave the nest within 24 hours of hatching and are independent at one month.  Sexual maturity is reached at 4-6 months.
Conservation Status: IUCN Extinct in the Wild

• Body length 28 centimeters, weight 170-300 grams
• Brown back, head (with a white stripe above the eye), and neck with a gray underside, striped with brown on the lower breast and abdomen.  
• Males and females look alike, but males are slightly larger
• Flightless (though it can flutter up to 3 meters) ground-dweller, they have well-developed leg muscles and are quick runners; they can also swim and even dive underwater
• The rail was driven almost to extinction by the brown tree snake's introduction to Guam, with the population in the low double digits by 1980.  It was last seen in the wild in 1987
• In the mid-1980s, 21 birds were captured to form a captive breeding population in Guam and the continental United States.  Reintroductions in snake-free zones are occurring
• The species is called the ko'ko in native languages

Islanders and Aliens

Happy Star Wars Day! (May the Fourth... as in, "May the Fourth be With You..." get it?).  What better day to talk about aliens... but not the Yoda kind.

The invasion of Guam by the brown tree snake was novel in one way - the invader was a snake.  If you'd replaced it with, say, a mongoose, or a stoat, or rats or macaques, or perhaps feral dogs or cats, however, you would've gotten a story which has played out across the Pacific, from the Galapagos to New Zealand to Hawaii.  Expand your search further, and you would have seen similar losses in the Caribbean, the Seychelles, Mauritius, and the Mediterranean.  The story plays out like this:

1. Island has unique wildlife, found nowhere else on earth
2. Island is visited by humans
3. Humans introduce domestic animals and/or invasive pests
4. Island looses unique wildlife, now found nowhere on earth

To be sure, extinctions occur on the mainland also, both because of invasive enemies as well as other causes (habitat loss, hunting, etc), but islanders seem to be especially vulnerable.  Part of it is that islands are small, and so the populations that live their tend to be small.  Makes sense - smaller the land mass, smaller the number of animals it can supports, easier it is for predators to kill all of said animals off.  Because the landmass is smaller, the animals that inhabit them also tend to be more specialized, which works great when conditions are stable, but is very problematic when they suddenly change.

Island animals, especially those that evolved in the absence of predators, also tend to be naive in the face of danger, a tameness that some visitors mistake for stupidity.  No bird exemplifies (or exemplified, emphasis on past tense) this more than the dodo, a hulking, turkey-sized pigeon-like bird from Mauritius, off the east coast of Africa.  Unaccustomed to the indignities of being hunted, the dodo waddled up the first sailor with a club, and was driven to extinction shortly after its discovery.  

The dodo calls to mind another problem that many island birds face when dealing with invasive predators - many are flightless.  It seems silly at first - flight is the most awesome advantage birds have over mammals.  Why give up that gift?  The fact is, flight is expensive.  It takes a lot of energy for a bird to fly, and it requires specialized muscles and feathers that are - biologically - costly to maintain.  Fear is biologically expensive, too.  Imagine if you ran away from every single thing you saw that could be possibly dangerous - strangers you see while out walking, cars, unfamiliar dogs, unexplained noises - you'd run yourself ragged in no time.  Time spent running is time not spent eating, or mating.  If an animal has no predators in its environment, it makes sense to loose this fear, and if there is plenty of food on the ground, and no need to get up high, why bother flying?  Current flightless island birds include the kakapo and kiwis of New Zealand, the flightless cormorant of the Galapagos, and the steamer ducks of the Falkland Islands.  

It all makes perfect sense when you look at it naturally.  The problem is that we've made this an increasingly unnatural world, and it's getting harder for specialized, predator-naive animals to survive.  Invasive predators have eaten their way through populations of many island birds around the globe, driving some to extinction.  Others are found only in captivity now, stranded in zoos and breeding centers until a safe release site can be located.  Sometimes, this means waging costly, difficult eradication campaigns to cleanse habitats of invasive pests.  In other cases, it means playing Noah's Ark and trying to establish new populations of birds on predator-free islands (which, ironically, involves introducing non-native species... again).

Some islands birds are lost and gone forever - the moas of New Zealand, the elephant birds of Madagascar - and nothing (at least right now) - can bring them.  For others, however - species which are still hanging in the balance - there is still time, still a chance to pull them back from the brink.  

Guam and the other Mariana Islands have birds in both categories.

Zoo History: Empire of the Brown Tree Snake

"But behavior, even in a pea-brained reptile, is surprisingly flexible.  On Guam, the snake forages as easily on the ground as in the trees, and it will consume anything that smells of blood... What scientists thought was one serpent is in effect two: the native and the colonist, the preinvasive and the postlapsarian."

- Alan Burdick, Out of Eden: An Odyssey of Ecological Invasion

By the 1960s, ornithologists studying the Pacific island of Guam knew that something was wrong – they just didn’t know what.  Before the startled eyes of scientists, the unique bird life of Guam – many of them species birds found nowhere else on earth – began to vanish, one species flickering out after another.  No one could agree on what the problem was.  Some said it was remnants of the pesticide DDT, still active in the environment years after its use.  Others suggested habitat loss, or maybe an introduced disease. 

The only known was that the southern third of the island was virtually devoid of bird life, and the line on “birdlessness” was steadily advancing.

In the 1980’s, biologist Julie Savidge was studying the extinction crises when she came across something she didn’t expect to find – a snake.  Guam had snakes, but they were tiny, worm-like things, not the large, active, muscular creature she found.  The species was identified as Boiga irregularis, the brown tree snake, known throughout Indonesia, New Guinea, and the Solomon Islands… but not on Guam.  Intrigued, she shifted her attention to the snakes and noticed a disturbing pattern – where the snakes appeared, the predator-naïve island birds disappeared.  She summed up her findings in a 1987 paper, “Extinction of an island forest avifauna by an introduced snake.”

In its native haunts, the brown tree snake is a modestly-sized, fairly cryptic species, a tree dweller that preys on arboreal birds (birds which have coevolved in the presence of the snake and are equipped to evade it) and is in turned preyed upon by monitor lizards and birds of prey.  On Guam, the snake found paradise – no predators, and prey that had never seen a snake as a threat before.  The damage was devastating – three of Guam’s endemic birds were eaten out of existence, whereas others now only exist in zoos and breeding facilities.  The brown tree snakes of Guam became different from those of Indonesia or New Guinea – bigger, more adaptable, more aggressive.  They eat the birds, yes, but have also learned to scavenge, everything from raw meat to canned dog food to bloody tissues.  Up to 40 snakes may be found on an acre of forest.  Here on Guam, Dr. Jekyll became Mr. Hyde.

How did the brown tree snake get to Guam – and, recently, onto other Pacific islands – in the first place?  It’s suspected that the brindled white-eye, Guam broad-bill, and other island birds are the last casualties of World War II.  During the war, American warplanes island-hopped around the Pacific, and it is likely that when they did, they carried stowaways.  Brown tree snakes can go a long time without food or water, allowing them to comfortably wait out a ride.  A female can store sperm for months, allowing a single gravid female to colonize an island.

Birds, lizards, and bats aren’t the only victims of the brown tree snake’s expansion.  It’s destroyed local poultry industries.  It’s been known to enter houses and bite people as it forages for food – the species is moderately venomous.  Most irritatingly, it has caused thousands of power outages.  Highly arboreal the snakes climb power poles, and their combined weight can bring the wires down.

There has been little success in controlling the brown tree snake.  Introduced diseases, poisoned baits, physical removal, snake-proof barriers – all tried with limited success.  Some scientists have quietly written Guam and other snake-infested islands off, focusing more on what can be done to prevent the expansion of the snake’s growing range.  Of all the islands in the Pacific, the most heavily guarded is Oahu, in Hawaii.  Hawaii is the crossroads of the Pacific in terms of commerce and transportation – from here, the snakes could get anywhere.  So far, a tiny handful of brown tree snakes have been captured on Hawaii (often with the help of trained dogs), but they are not believed to be established… yet. 

The US government uses posters like this to help people identify and report spreading brown tree snakes

The fight to limit its spread continues, but it is still to be seen what island is the next to fall to the brown tree snake.

So, how does this all count as “Zoo History?”  Later this month, we’ll be showing how zoos have been involved in the struggle to save Guam’s remaining bird life from extinction.

Mariana May

This month, I'm going to try to do something a little different with the blog.  For the first time, I'm going to have a monthly theme, focused around one topic, a topic which many zoos and government agencies have been dealing with for years, but one which hasn't received too much attention from most people (certainly less than global climate change or poaching).  That topic is the avian extinction crisis of the Mariana Islands.

Though governed by the United States, the Mariana Islands are the most far-flung parts of the country, lonely crescent of islands south of Japan, north of New Guinea.  As with many islands far removed from land, they are home to unique creatures found nowhere else on earth... and that unique wildlife - especially the bird life - is under siege.  For the ornithologist, the Marianas must have seemed an Eden of friendly, beautiful birds, evolving in a world free from danger.



Every Eden, as we'll see tomorrow, has a snake, however...