Reptilian invasion: Saving Pacific island birds from snakes
St. Louis Post-Dispatch
By Jeffrey Bonner
September 7, 2008
In the ninth of a monthly series this year, Saint Louis Zoo President Jeffrey Bonner explores a part of the globe where the Zoo is working to conserve threatened species, protect natural habitat and partner with other organizations to strengthen the web of life in which we all live. See story this story in St. Louis Post-Dispatch.
The Mariana Islands are a beautiful Pacific island chain north of Papua New Guinea and southeast of Japan. They were occupied by Japan in World War II until the United States took them by force to use as a staging ground for invading the Philippines and bombing Japan. After heavy fighting, the Allies took Saipan and Guam, the southernmost island in the chain, in August 1944.
One of the indirect consequences of these battles was the loss of eight of the 11 native bird species of Guam, including my favorite bird, the Guam kingfisher, properly called the Micronesian kingfisher. Ironically, the fighting did not directly cause the bird's demise. Military ships traveling from New Guinea to Guam brought in their holds some deadly stowaways: brown tree snakes.
Mildly venomous, like most rear-fanged snakes, they had a variety of natural predators in New Guinea, but none on Guam. Within a few years, their numbers shot from a handful to about 10,000 snakes per square mile. (To give you an idea of such density, a common cause of power failures on Guam is the weight of brown tree snakes on utility lines.) The snakes ate almost every single bird on the island, including the Guam kingfisher, which survives today only in zoos - including ours.
New Risk In Saipan
It appears that the brown tree snake has expanded its range from Guam to Saipan. When it becomes a fully established predator, the birds of Saipan will be at extraordinary risk. Surveys of birds on other islands where the snake has migrated suggest that a 90 percent decline can be expected within eight years. If the experience of the Guam kingfisher is any indication, many of Saipan's 11 species of forest birds will simply go extinct.
Introducing predators - including hawks, eagles and owls - into the snake's native range isn't an option because many would also prey on the Guam kingfisher.
Guam is one of the major transportation hubs of the Pacific. While the brown tree snake (pictured at left) originally escaped from New Guinea by boat, it clearly doesn't mind traveling by air. And that could mean that its next stop may well be Hawaii, where eight sightings have been confirmed since 1981.
The St. Louis Zoo is one of a few zoos in America that breed the Guam kingfisher. As I write this, 102 Guam kingfishers are left alive on our planet - five of them here.
So, too, are the prospects for the birds of Saipan. But this time we are not waiting until the birds approach extinction. Five zoos, comprising the Honolulu Zoo, Louisville Zoo, Memphis Zoo, Audubon Zoo and ours, have banded together with the U.S. Fish and Wildlife Service to form a group called the Mariana Avifauna Conservation project, or MAC project.
How to Breed 11 Endangered Species
Our first goal is to figure out how to capture, hold, transport and, eventually, breed all 11 species at risk. This will allow us to establish secure populations in U.S. zoos. Our second goal is to move birds to other islands where the brown tree snake has not yet arrived. Finally, the MAC project needs to educate the islanders on the dangers of accidentally transporting tree snakes. The project is raising money to train the people of the Marianas to monitor the birds and, of course, the snakes.
So, how are we doing? In 1996 Michael Macek, our curator of birds, brought Mariana fruit doves (pictured at right) to our zoo. We currently have three pairs that are reproducing very well for us. In 2002, Michael and Anne Tieber, our zoological manager for birds, returned to the Marianas and collected four pairs of white-throated fruit doves. This year we had four babies. We're not doing quite so well breeding "Goldies," the beautiful Saipan golden white-eye, a small bird that resembles a canary. Fortunately, we have been able to move 20 Saipan bridled white-eyes to a snake-free island called Mañagaha, a small islet off the west coast of Saipan.
So what does this reptilian invasion in the Pacific have to do with us in the heartland? Our country is constantly under siege. Our rivers teem with huge carp and zebra mussels, our ash trees are under threat and we will soon be seeing armadillos in Affton. Some of these invaders are relatively harmless, but others can be catastrophic.
It is possible to conduct eradications on islands far more easily than it is to win the war against invasive species on a continent the size of America. Saving the birds of Guam and Saipan may not be an exercise in futility. Just because we don't yet know how to rid these islands of tree snakes doesn't mean that we won't someday figure out how to do so.
But in both instances, the first rule of intelligent tinkering applies: Save all the pieces.
Republished with the permission of the St. Louis Post-Dispatch
Copyright 2008 St. Louis Post-Dispatch
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