Most property owners, about 400 so far, have gladly allowed trappers to remove nutria for free. But some have balked, suspicious of government programs or reluctant to have activity on their land during waterfowl- and deer-hunting seasons. Each agreement must be negotiated separately to include any landowner stipulations, a time-consuming process.

"If we want this to be effective, we need everyone's cooperation," Kendrot said.

The Judas Project was adapted from tracking programs used on feral hogs and goats. Nutria are captured and sterilized. Sometimes, a telemetry device is implanted in the body, but more recently the animals have been fitted with $1,200 GPS collars.

The units take location readings every 90 minutes and store the data. After several weeks, trappers locate the animals and recapture them to retrieve the collars and download the information. In the case of Judas 760, travel was fairly extensive — about four miles — and occurred at night. The data allowed them to set traps along paths favored by the animals.

Kendrot and his staff are hoping to get the money to make more Judases and to pay for real-time readings so they can act more quickly to snuff out infestations.

Meanwhile, the nutria team is trying to find the perfect scent to lure nutria into traps, an effort being led by Robert Colona, a biologist with the U.S. Fish and Wildlife Service.

Colona is field testing about 35 ingredients, everything from cherry essence to nutria glandular secretions. The odor has to have range and staying power to work in the wild.

Biologists place experimental scents on swabs attached to bamboo sticks along well-known marshland paths. Then they install a wildlife camera to monitor the reaction of wild nutria. Most concoctions barely raise a whisker. The tinkering continues.

Colona also tries out scents on a captive population kept in pens at Blackwater. The winner so far? "Southwestern chipotle hummus," said Colona, laughing.

Then he grows serious. "The finish line is in sight," he said. "But if we can't develop an effective lure, we won't get the last one."

candy.thomson@baltsun.com