Monday, March 08, 2010

THE GREAT ANT ESCAPE

It took humans about three years and countless hours of planning to rebuild San Francisco's California Academy of Sciences—but less than a year for the leaf cutter ants to figure a way to bust out.
Thousands of ants on exhibit at the museum were put under lockdown last summer after workers discovered they had bored passages inside a feeding tree near their nest in a mock rain forest, which allowed them to flee their enclosure. A new artificial tree has been installed, but officials say the ants will remain locked up for a few more weeks until officials can be sure they don't escape again.
"The ants decided they would like to expand their territory—and proved that they were smarter than the humans who designed their display," says Stephanie Stone, an academy spokeswoman.
Much has been written about the wonders of the academy since it reopened in Golden Gate Park in September 2008 after a $500 million revamp. The academy now boasts a state-of-the-art environmental design with a planted "living roof" and popular attractions such as a living coral reef and a four-story tropical rain forest. Almost three million people have visited since the reopening, allowing the nonprofit to break even on expenses, officials say.
Still, academy officials say a few creatures are besting their carefully laid plans. As a result, workers are having to wage a behind-the-scenes battle against some of the museum's 38,000 living specimens.
One conflict involves a 12-inch monitor lizard, which last spring burrowed into some openings in the articifical rock behind its cage. That forced biologists to use a tiny remote camera to find its hiding place. New rockwork with no openings was later installed, say officials.
In the academy's Steinhart Aquarium, workers have been trying unsuccessfully for two months to remove a zebra moray eel so a veterinarian can inspect a growth on its head, says Bart Shepherd, the aquarium's curator. But though the eel resides in a relatively small, 300-gallon tank, he says it has figured out how to elude capture by wedging itself in some rocks.
"We want to have all these animals under control because this is a controlled environment," Mr. Shepherd says. "But when you reproduce the natural environment, then they have an advantage."
The academy's biologists have learned from some past mistakes. About 10 years ago, Mr. Shepherd says, crabs kept mysteriously disappearing from a tank in the old academy. The culprit was a giant octopus two tanks over, which used its tentacles to sneak out at night and snatch crabs, he says. The octopus tank has since been wrapped in AstroTurf.
In the new academy, officials thought they had designed a foolproof enclosure for the leaf cutter ants, so named because they cut leaves to make fungus gardens. The ants' nest was embedded in rock made of concrete and fiberglass, with windows for visitors to watch. A vine made of plastic connected the nest to a 20-foot-tall tree stump also made of concrete and fiberglass. It was put in a pond away from other trees, so the ants would have no way to escape to the rest of the forest, says Mr. Shepherd.
For months, visitors marveled as the leaf cutters marched along the vine. But in June, biologists noticed the ants were going inside the stump and not back to their nest. They discovered the colony had excavated new nest chambers in the foam inside the stump by chewing up and carting out tiny pieces of the fiberglass. They also had built a network of fungus gardens inside.
If the ants had escaped, officials say the critters could have damaged mahogany and other trees in a 90-foot-diameter glass dome enclosing the rain forest. "What we don't want is for them to be free-ranging the forest," Mr. Shepherd says.
Academy workers quickly locked the ants inside their old nest, giving them access only to an "ante" chamber built into the same artificial rock where leaves are loaded in for them to harvest, Mr. Shepherd says. Workers recently installed an eight-foot-high stump, which this time was filled with concrete and topped with a large plastic bowl where leaves will be placed. The sides of the bowl are coated with liquid Teflon to discourage climbing.
Meanwhile, a new vine is being constructed to the ant nest 15 feet away. "We'll see if this works," Mr. Shepherd says, adding that he hopes humans this time will outsmart the ants.
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