A campaign to rid South Florida of pythons and other large invasive snakes may never be won, but wildlife biologists are taking a stand in the Florida Keys.

"Our goal is to try to pick up the few pythons that make it to the Keys before they can become established," said Bob Reed, a snake expert directing invasive-snake efforts for the U.S. Geological Survey.

"Because of the large natural gap between the mainland and the islands, it is one of the few places where we have a good chance of successfully containing the python population," Reed said this week from his Colorado office.

The effort gained new attention Aug. 30 when a large python was tracked and captured near mile marker 105 on Key Largo. That snake officially measured 9 feet, 4 inches, somewhat smaller than initial 11-foot reports.

The bad news was that it was female capable of breeding. The good news is that it was confirmed to be a virgin snake with no eggs.

"About a dozen" pythons have been killed or captured in the Keys since the first was recorded in 2007 on North Key Largo, Reed said.

"Most have been medium-size adult males," he said, "probably moving widely to look for females during breeding season."

Some may travel south along U.S. 1; several have been killed on the 18-Mile Stretch. Others, however, may swim from the mainland, Reed said. "Pythons are quite good at swimming."

It's "probably rare for a python to go long distances" across open water like Florida Bay, he said. Other areas, like near U.S. 1, provide "all sorts of mangrove corridors with only a few open-water gaps," he said.

Former state biologist Jim Duquesnel now works for the Geological Survey with another specialist to help patrol the Keys. The National Park Service, Florida Fish and Wildlife Conservation Commission and other government agencies are working on the snake problem.

The Geological Survey maintains about four dozen coffin-like python traps on North Key Largo and southern Miami-Dade County. The six-foot-long, canvas-covered traps are baited with live rats. However, labor needed to tend the traps (which includes feeding or replacing the rats) with few captured snakes means the trap program will shut down soon.

The invasive-exotic snakes, which started as escaped or released pets, have taken a firm hold in South Florida's mainland. More than 1,500 have been killed or captured but the lowest population estimate stands around 10,000 constrictors in the region's expansive wetlands. The number may be significantly higher, Reed said.

"The public may be able to access only 1 or 2 percent of Everglades National Park so the probability of detecting an individual snake are low," Reed said. "We don't have any actual tools for a complete eradication."

Biologists now focus on protecting critical bird rookeries and sensitive areas like the Keys. Pythons and boa constrictors are not considered serious threat to humans but do prey on native species.

"The public is most important tool we have," Reed said. "If a snake in the Keys is bigger than you are, there's a real good chance it's a nonnative. We want to know about it."

A Florida Keys hotline established by The Nature Conservancy to report big snakes -- (888) 483-4681 -- has now gone statewide.