On the trail of elusive basilisk lizard

April 15, 1994|By David Michael Ettlin | David Michael Ettlin,Sun Staff Writer

Sandy Barnett played an electronic game of hide-and-seek yesterday with the basilisk lizards in the National Aquarium rain forest, and -- as usual -- the lizards lost.

The game is played several times a day, with Ms. Barnett, the Aquarium's senior herpetologist, carrying a small black tracking receiver to pick up signals from the tiny, battery-powered transmitter carried by each of the forest's four brown basilisk lizards.

"I don't know of any other institution doing this in a captive zoo environment," Ms. Barnett said of the radio telemetry -- a system more commonly used by scientists to keep track of animals released in the wild.

Ms. Barnett embarked in November on the unique 100-week project to gather information on the critters -- known by their scientific name as Basiliscus basiliscus, but sometimes called the "Jesus Christ Lizard" for their ability to run across water.

The lizards -- two males and two females in the forest, and two other females kept away from the exhibit in a controlled environment -- were captured in Costa Rica during a 1992 Aquarium expedition in a real rain forest.

The purpose of the study, in large part, is to monitor the activities and health of the hard-to-find animals in the simulated rain forest in the pyramid-shaped upper level of the Baltimore Aquarium.

If they would just run across water, the lizards might be easier to spot -- running with such speed, Ms. Barnett said, that "it's

comparable to skipping a rock on water." (The lizards have an extra fold of skin on the sides of the five digits on their hind feet to facilitate that ability.)

"A young basilisk lizard can run 60 feet over water," she said. The heavier adults sink a bit in the water and seem "more like motorboats" as they flee a predator or pursue their own small prey, she noted.

But there's not much room or opportunity for such watery high jinks in the Aquarium rain forest. Instead, the arboreal animals, cousins to the larger iguanas there and looking a bit like miniature dinosaurs, blend in with the vegetation.

Their mostly brown bodies provide camouflage as the lizards sunbathe atop leaves or cling to the stalks of foliage in the upper reaches of the forest.

And that's another reason for the radio telemetry, in which Ms. Barnett is assisted by other staff members, volunteers and sometimes by visiting students.

Several times a day, the antenna will be aimed around the forest to pick up the strongest signal from the transmitters -- each lizard beaming out a different frequency.

The information enables exhibit guides to point out areas where the lizards -- among the hundreds of animals and 450 species in the forest -- are most likely to be spotted.

It is part of the thrill of an Aquarium visit to find not only the bright and obvious animals in the rain forest, but also the hidden wonders. There are about 500 frogs, three dozen birds, a dozen turtles, eight lizards and four tropical mammals (two-toed sleepy sloths and the golden lion tamarin monkeys.)

Yesterday's electronic pursuit of the brown basilisk lizards differed slightly from the daily venture because Ms. Barnett also set out to capture them for a physical exam -- checking weight and length, a radiograph to assess bone density, blood tests to determine calcium levels.

The transmitter, less than an inch long, is attached by a single suture to a bony crown on the animal's back. "We tried to develop little backpacks, thinking it was the most comfortable way for them to carry their batteries," Ms. Barnett said. "But they're little Houdinis -- they wiggled out of the harnesses."

It took about 30 seconds yesterday morning to pick up the first LTC signal, but more than 30 minutes to capture the animal -- concealed in a tangle of vegetation. "We were right next to the animal and didn't see it," Ms. Barnett said.

The Aquarium staff hopes to find out not only whether the brown basilisk lizards thrive in the exhibit, but how readily they can be seen by the public. With the daily telemetry to help, there are frequent sightings -- and growing data to show what forest furnishings the lizards like.

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