Costa Rica's "Problem Crocs" Return After Removal

September 26, 2003

Over a few weeks, a big American crocodile repeatedly lumbered into a village near Costa Rica's Tarcoles River and devoured some local dogs—not an unlikely occurrence in this region. Here, Pacific coastal development is bringing more people into crocodile territory—and tourists feed the crocs, helping them shed their natural fear of humans.

Unlike most countries, Costa Rica doesn't eradicate "problem crocs," but relocates them to less populated areas. But new tracking research suggests that for crocs, there's no place like home: 82 percent of displaced crocs returned, from as far as 62 miles (100 kilometers) away.

"As soon as you let them go, they seem to turn around and head home," said Perran Ross, a biologist at the Florida Museum of Natural History in Gainesville and coordinator of the Switzerland-based World Conservation Union's crocodile specialist group.

Brady Barr, a herpetologist and field specialist, and his colleagues trail and capture some of these "problem crocs," following their tracks to the river.

They often pursue these massive, aggressive males at night. From small boats, they shine bright spotlights across the water, searching for the unmistakable golden shine of crocodile eyes. When they locate the culprit, they temporarily blind the animal with the lights while Barr slips a metal snare over its head.

Relocating Crocs

Then they tow the animal to shore. It takes two or three men to subdue these 11 to 15 foot (3.5 to 4.5 meter) crocs, which weigh as much as 1,500 pounds (700 kilograms). They attach a radio transmitter to his tail, collect tissue samples for DNA analysis, blood for toxicology work, and take measurements.

"We gather as much data as possible because it's not easy to get your hands on a big croc," said Barr. "It's dangerous, not only for us, but for the crocs—but the payoff in terms of scientific data can be huge."

Then they tape the animals' jaws securely shut, load it into the back of a pickup truck—and drive it to another river some miles up or down the coastline.

Barr's primary reason for radio tagging 20 crocodiles over the last three years is to track them in their new environs.

Returning home after relocation is a risky, arduous journey. Crocs must swim downriver to the sea, where they encounter a maze of fishing trawlers with giant nets. Sometimes they must swim long distances in the open ocean—and during their entire voyage, they must avoid poachers.

This homing behavior has been documented in other parts of the globe. The Australians attempted to relocate some large saltwater crocodiles living near Darwin with the same results, said Ross. Problem American crocodiles in Florida were relocated at one time, but when it proved ineffective, wildlife managers changed tactics. Now they shoot them.

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