February 25, 2009
Crocodiles Being Repelled By Magnets
An experiment has been launched by Florida wildlife managers to see if they can keep crocodiles from returning to residential neighborhoods. It is hoped that their "homing" abilities will be disrupted by placing magnets on their heads.
According to a report in a biology newsletter by researchers at Mexico's Crocodile Museum in Chiapas, there was some success with the method, using it to permanently relocate 20 of the reptiles since 2004.
Crocodiles are known to be territorial, and when biologists move them from urban areas to new homes in the world, they tend to go right back to the place where they were captured, traveling up to 10 miles a week to get there.
According to scientists, crocodiles rely on the Earth's magnetic fields to navigate, and that taping magnets to both sides of their heads disorients them.
"They're just taped on temporarily," Hord said. "We just put the magnets on when they're captured and since they don't know where we take them, they're lost. The hope would be that they stay where we take them to."
Hord and his co-workers tried it on two crocodiles since launching the experiment in January, attaching "a common old laboratory magnet" to the sides of the animals' heads. Hord said that one got run over by a car and died, but the other has yet to return.
American crocodiles' numbers have gone from being once an endangered species to nearly 2,000 in coastal south Florida, their only habitat in the continental United States. That creates an increasing number of contact with humans in areas where backyards border on canals around Miami and the Florida Keys.
Hord said that crocodiles are still classified as a threatened species, so game managers are reluctant to move them to new areas where they might be killed battling other resident crocodiles for turf rights. He added that unlike alligators, which are more numerous, each crocodile is considered important to preserving the species.
"These crocodiles are unique and valuable creatures and we feel like we have a responsibility to live with these animals as much as we can," he said.
According to Hord, many frightened residents do not share that view, although crocodiles are shy creatures. Wildlife managers are trying to relocate any thought to pose a significant risk, mainly those that seem to have lost their fear of humans.
Most crocodiles in Florida are tagged when they are hatchlings, that way biologists can easily recognize them, said Hord.
Any of the reptiles that come back twice after being captured are moved to zoos or otherwise placed in captivity, something biologists hope to avoid if the magnet experiment works.
"This one is by no means a really well-developed scientific study with a control group. It's just something we thought we would try," Hord said. "We do have to make some room to live with them."
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