Tracking North America's largest snake

The eastern indigo snake, which can grow up to 8 feet long, perplexes biologists who study them

  • Don Stap
  • Oct 01, 2001
STEPHANIE IS MISSING. There has been no sign of her for three weeks. Biologist Rebecca Smith, who has been keeping an eye on Stephanie for the past year, says that there's no point in looking for her now. It is cool and overcast on this December day in central Florida, so Stephanie is probably holed up somewhere, trying to stay warm. Stephanie, after all, is cold-blooded. She is, in fact, one of 74 eastern indigo snakes that Smith has outfitted with radio transmitters during the past three years while trying to answer basic questions about the life of North America's largest snakes.

The elusive eastern indigo snake--a subspecies of the indigo snake, which ranges from Georgia, Florida and Texas through South America--has been federally protected as a threatened species since 1978. But because so little is known about the snake, not much is being done to protect it. "There have been very few studies of any kind and hardly any data published," says Smith. "We don't even know how often females reproduce or how long indigos live in the wild." As long as such questions remain unanswered, it will be hard to halt the population decline that appears to have eliminated the snake from most of its former range.

Eastern indigo snakes, once found from Mississippi to South Carolina and south through the Florida peninsula, today occur only in southern Georgia and Florida. But even in most of these areas the snake is becoming increasingly rare. Habitat loss and fatal encounters with cars have contributed significantly to the population decline. There are other reasons for their dwindling numbers: Some people kill indigo snakes simply because they are snakes, while others--poachers--collect them for the pet trade.

An adult eastern indigo is typically six or more feet long. (The record is eight feet, seven inches.) The snake is entirely iridescent black except for a pale wash of coral red along the throat and upper belly. Nonpoisonous, it is still a powerful predator, pinning down its victim to subdue and swallow it alive. The indigo makes a meal of frogs, turtles, lizards, fish, birds, small mammals and occasionally even rattlesnakes. But it is remarkably docile in the presence of humans.

Its affinity for people might explain why Smith and her colleague in the study, Mike Legare, name the snakes they capture. Smith says it's simply easier to use names than numbers to identify them.

This afternoon, with Stephanie nowhere to be found, Smith heads off to look for Odie. Legare had located this snake earlier during a morning aerial survey. Like Stephanie, Odie needs to have his transmitter replaced. The batteries only last a year.

Smith meets Legare on the outskirts of an industrial park just outside the Kennedy Space Center, where both wildlife biologists work as private environmental consultants to NASA. Legare leads the way down a sandy path into woods dominated by palmettos, wax myrtles, scrub oaks and longleaf pines. They have to bull their way through the dense undergrowth of palmettos but stop repeatedly while Legare moves the antenna of his radio receiver in the air, listening to the beeping signal that is coming from Odie's transmitter.

Within 20 minutes Legare locates Odie beneath the ground at the base of a palm tree. Although indigos may roam widely by day, actively searching for prey, they remain in burrows when the weather is cool. Smith and Legare know this all too well: They've brought a shovel. The idea is to dig a hole into the burrow, spot the reptile and grab it with a snake stick. It's a good idea. But after an hour and a half of trying to get past the palm tree's dense mass of roots, the researchers have created only two small holes. And there's been no sign at all of Odie.

Aware that daylight will run out soon, Legare gets on his knees to dig with his hands, ripping up dirt and roots like a dog. Suddenly, he stops. "I see him. Don't anyone move," he says. Moments later Legare has a handful of snake. He pulls Odie out of the burrow and hands him to Smith. The big snake seems unperturbed despite this rude interruption of his nap. And that is a good thing because Smith has to carry him back to the car in her arms; no one has remembered to bring a snake bag along on the outing. Smith holds Odie over her head and struggles through the thick palmettos. Odie, curled around her arms, calmly surveys the woods from his new vantage point.

When a new transmitter is implanted in Odie later this afternoon, Smith and Legare will be able to follow him for another year thanks to the funding and efforts of a private wildlife trust, the U.S. Fish and Wildlife Service and NASA. But Smith is concerned that this support will only provide enough time and resources to track the snakes. "We also need time to analyze the data," Smith says.

She points to preliminary findings that are already cause for grave concern about the indigo's life in crowded central Florida. "We were surprised with how many snakes we found in residential areas," Smith says. "The mortality rate for snakes in those areas is high."

Only one of seven male indigos found in this highly fragmented habitat is still alive, and only three of eight females. During their once-a-week tracking, Smith and Legare have found snakes under people's porches, beneath air-conditioning units, and, in one case, cut up in several pieces and buried in a man's backyard, transmitter and all. Six other snakes have disappeared mysteriously. Six more have been hit by cars, some probably intentionally.

Overall the mortality rate is surprisingly high for a large snake with few natural enemies. Only 45 percent of the snakes that have been tracked for nine months or more are still known to be alive. Smith stresses that her data are inconclusive, and she worries about the future. "The indigo snake is in trouble," she laments, "and it's a snake after all, so it has two strikes against it to begin with."

To know the extent of the problem, scientists need to study the indigo snake throughout its range. Trapping snakes is difficult, but Smith is intrigued by the possibility that females give off a scent that attracts males. If it can be reproduced synthetically, it could be used to lure males into temporary traps.

But perhaps the most important information emerging from the study is that indigos live in varied habitats--from swamps to sandy pine uplands. If the snakes can adapt to different environments, their chances for survival are greater.

For now, though, Odie has an appointment with a veterinarian, and Legare is already talking about making plans to get back up in an airplane tomorrow to track with the radio receiver. Stephanie is out there somewhere.

When he is not tagging along in the field with snake scientists, journalist Don Stap teaches creative writing at the University of Central Florida in Orlando.

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