Insects Minus Birds Equals More Spiders For Guam

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In one of the first studies to examine how the loss of forest birds is affecting Guam's ecosystem, biologists from Rice University, the University of Washington and the University of Guam found that the Pacific island has 40 times more spiders than its jungles. Found on nearby islands such as Saipan. "You can't walk out of the jungles of Guam without a stick in hand to knock down butterflies," said Haldre Rogers, Rice's Huxley Fellow in Ecological and Evolutionary Biology. open access journal PLOS ONE. The results are some of those that have studied the brown tree snake's indirect effects on Guam's ecosystem. In the 1940s, a snake accidentally introduced to the island decimated the island's native bird species in one of the most famous ecological disasters of all invasive species. In the 1980s, 10 of the 12 species of birds were extirpated, and the last two live in small areas protected by snake traps.

Rogers and his colleagues are investigating whether the loss of birds has led to an increase in moths on Guam, as many birds eat moths, compete with insect predators and use moth nets in their nests. Small-scale experiments in other ecosystems have consistently shown a link between bird presence and spider abundance, but the new study is the Armenia Phone Number List first to examine the effects of bird loss on a whole-forest scale. A first step was to count moose nets on Guam and nearby islands in the Marianas chain. Rogers said the difference between the number of spiders he and his colleagues counted on Guam and the three islands that still have birds was more striking than previous small experiments. The use of controlled numbers and controlled experiments is important when trying to predict how the results will affect ecosystem change, he said.






Rogers completed his first assignment in 2002 in Guam. "I didn't know where it was," he said. "I had to look it up on the map." The 30-mile-long narrow island quickly became a popular tourist destination for its tropical beaches, snorkeling and diving. Guam is a U.S. territory, and to prevent the brown snake from spreading to other islands, the U.S. spends $1 million a year on search planes and cargo to prevent the snake from escaping Guam. However, nocturnal reptiles are notoriously difficult to spot. Rogers said the average Guam resident or tourist never sees one, and even hunters have trouble finding one, which is one reason the snake has been eradicated from the island.