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Python-palooza!

Monster-sized Burmese python bearing record-number of eggs retrieved in the Florida Everglades

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Her name is P-52. It doesn’t sound all that special. But she broke records earlier this year as the largest wild Burmese python ever found in the United States. At 17.7 feet long (5.36 meters), she weighed a whopping 164 pounds (74.4 kilograms). When researchers at the Florida Museum of Natural History opened her up earlier this month, they found 87 eggs — also a record.

Although Burmese pythons are native to Southeast Asia, thousands are born in the wilds of Florida each year. The first one was spotted there in 1979. Some biologists now suspect the first pythons roaming the state had been cast-off pets. They either escaped or their owners released them when the snakes got too big to manage. It’s also possible that breeders released some when they got more pythons than they needed. Since 1990, pet suppliers have imported more than 100,000 of these snakes into the United States.

In the late 1980s their numbers were so low that it “was difficult to find one because of their cryptic behavior,” notes Kenneth Krysko, who works at the Gainesville, Fla., museum where P-52 was examined. By cryptic, he means these reptiles can blend in with their surroundings. So even pythons 12 feet long or more can be quite difficult to see when they’re not moving.

But their numbers have so increased that finding them is proving pretty easy. They’ve been breeding in Florida’s Everglades National Park for more than a decade. “Now, you can go out to the Everglades nearly any day of the week and find a Burmese python,” Krysko observes. “We’ve found 14 in a single day.” Biologists don’t know how many pythons are now living in southern Florida, but estimates range from 30,000 to 80,000 or more.

Finding the record-size python proved somewhat of a welcome accident for snake watchers, notes Kristen Hart, a U.S. Geological Survey ecologist in Davie, Fla. Two members of her team had been sent to walk into the Everglades and observe a python known as P-46 (the P denoting the animal was a python).

Earlier, Hart’s crew had implanted this male with a radio transmitter (and a backup, in case the first failed). Once a week thereafter, the researchers marked the snake’s position within the swampy national park from the air, by plane — and from the ground, in person.

On March 6, the two-man crew tramped a mile or so into the park for an on-the-ground sighting. Their job: to not only confirm the snake was alive but also to record its habitat (the precise environment in which it was found). While observing P-46, the men heard a rustling in the brush nearby. Because this was breeding season for snakes, the crew investigated whether the sound might signal the presence of another python. And that’s when they stumbled onto P-52.

They wrestled the mammoth snake to subdue her — one man holding her tail, the other her head. It wasn’t easy. As Hart describes her, this python was just a heavy “tube of muscle.”

When the snake finally tired, the two men hoisted her onto their shoulders — yes, alive — and carried her back to their truck. It took hours, stumbling over rocks and getting scratched by saw grass and other brush and occasionally caught by vines.

Back at the lab, three days later, Hart’s team implanted four devices into the snake: two radio-transmitters, a GPS device to track the precise ground coordinates of the animal at all times and an accelerometer. The last device can measure movements in three dimensions. The scientists then released the enormous snake back into the Everglades.

Each device recorded or broadcast its position four times a second. That’s 345,600 times a day. Powering the instruments to do this put a big drain on their batteries. That’s why the devices had a useful life of only about 40 days.

So on April 19, 38 days after returning P-52 to the Everglades, scientists trekked back in and caught her one last time. Back in their lab, they removed her tracking instruments, killed the snake and stored her body for study. Those investigations began on August 10.

Unmasking the snake’s behavior

Burmese pythons are invasive snakes, meaning they are invading territory to which they are not native. And these big and hungry snakes are proving especially destructive to the ecosystems of southern Florida. The National Park Service has a rule that when such invasive species are found, they must be killed to limit the damage they can do.

Hart’s team must petition the park service to temporarily ignore that rule in order to catch and release pythons in the Everglades. It’s the only way the scientists can begin to understand the behavior of these animals, Hart explains. Despite the snakes’ huge numbers, she observes, a lot of basic questions remain unanswered, such as: How often do they breed? How far do they travel in a given week or month? How often do they eat?

One might expect that finding answers would be as simple as phoning reptile experts in Southeast Asia, where the snakes come from. “And we are talking with scientists there,” says Michael Dorcas, at Davidson College in North Carolina. “Unfortunately,” he has learned, “we probably know more about pythons in south Florida than about them in their native range.” The reason: Scientists have not studied the snakes much where they developed and became a natural part of the landscape.

As a herpetologist, Dorcas is a biologist who specializes in reptiles and amphibians. But he’s also an ecologist, which means he tries to understand how an animal fits into its environment — or doesn’t. And many invasive species, like this python in Florida, have the potential to totally disrupt and alter an environment that’s new to them. This typically occurs if an incoming species lacks predators. Without something higher up the food chain to eat them and keep their numbers in check, members of an introduced species can transform an ecosystem.

Dorcas’ work has helped establish that Burmese pythons have indeed been bullying their environment. Earlier this year, he led a group of scientists who showed that the snakes have been eating their way through the Everglades, leaving a drastically changed ecosystem in their wake.

Raccoons, opossums, deer and other mammals, along with birds and alligators, have all turned up in the stomachs of captured pythons. And the scientists found that as soon as the pythons expanded into a new area, the number of prey animals there fell. In portions of the Everglades where these pythons have been present longest, certain prey species appeared to nearly disappear, Dorcas told Science News.

Loving Florida

One big advantage that Burmese pythons have over many of their prey — a slow metabolism. This is the rate at which body processes occur. Being warm-blooded, mammals and birds breathe quickly and circulate their blood rapidly to regulate their body temperature. Powering these processes takes a lot of energy obtained from food. Cold-blooded pythons, however, don’t need food to fuel their body temperature.

This “allows pythons to do things that we can’t,” Dorcas says. “For example, in many instances a large Burmese python, if it’s healthy, could go a year or more without eating.” So if the number of prey animals falls, a python just rests quietly and waits for prey to reproduce. Rabbits, deer and birds can’t survive months — or, in some cases, even days — waiting for their next meal.

Hart points to another of this snake’s advantages. Unlike many baby animals that are vulnerable at birth and need some time to adapt to their environment, “Baby pythons are just raring to go, right out of the egg.”

These animals are also quite comfortable in the Everglades. Although they need freshwater to survive, they don’t need to drink it. They can get the water they need from the bodies of the animals they eat, Hart says. And the snakes are fine swimmers. Her team has observed some traveling across seawater, far from land. That seems to explain why Burmese pythons have been found on islands (known as the Keys) that are at least 18.5 miles (30 kilometers) off of the Florida mainland.

The main limitation in their moving onto those islands would be access to freshwater, for drinking, along the way. But especially after a storm, Hart notes, rafts of floating debris often develop. The cratered surface of a branch, the cupped surface of leaves or a piece of plastic could all hold tiny pools of freshwater. Or a floating yogurt cup might collect a bit of rainwater. Hart suspects these snakes are quite adept at finding enough freshwater from sources such as these, even while at sea. “So it’s not inconceivable,” she says, “that these snakes can go from island to island.”

Keeping track

Hart would like to try and confirm the snakes’ island hopping by fitting those in coastal areas with tracking devices. But there are two problems with that idea right now.

First, to slow the snakes’ spread, there’s that park requirement that scientists kill all pythons that they find. “So it would be a little dangerous to put them out at the coast, where they might swim away,” she says — even though this “may be the only way that we can determine how long it takes them to get a certain distance across a saltwater barrier.” Second, tracking devices can be damaged or destroyed by saltwater. And that means that if a snake did go to sea, scientists might lose their ability to later find and recapture it.

Tracking devices are changing all of the time, however. So it’s possible that newer models will allow good real-time tracking of snakes, even at sea. Such devices could deliver valuable information about where to boost snake surveillance programs, Hart says.

Each Burmese python that receives tracking implants provides a wealth of new data for scientists. For instance, those devices used in P-52 will show where and how often she ate. Key to that information will be the accelerometer she carried. It recorded how she moved — such as whether she traveled in a straight line, rolled or coiled. That last movement can be particularly telling because pythons are constrictors. That means they kill by wrapping around their prey and slowly, steadily wrapping tighter until their lunch can no longer breathe.

“They often constrict with a type of motion where their belly goes up,” Hart explains. “And that’s not a normal position for a snake.” So her team looks for those belly-up movements, how long they lasted and where the snake was when it occurred. By matching the precise times of these movements with GPS data on the snake’s location during those periods, her team can begin to identify the habitat in which the snake had been dining. Was it a gator’s pond? In a tree? Or perhaps in a dense thicket at night?

By counting the number of those feeding events and comparing them with weather records, biologists might also learn whether feeding increases when it’s rainy or hot. They might even identify whether the snakes are more likely to snack during seasons when slow and unwary baby mammals are first venturing out into the environment.

Tail data

Scientists would like to know how closely related the Everglades pythons are to one another. To study this, Hart and other biologists snip off a piece of the tail of every python they catch. Then they record its DNA to compare against that of the other pythons caught in Florida.

If the DNA show these animals are very closely related, this would suggest that just a few initial snakes served as the great-great-great grandparents of all pythons in the Everglades. Put another way, that would mean the release of just a few snakes launched the huge, bullying assault this species has been carrying out on the Everglades’ ecosystem. But if many of the snakes show little relatedness, that would indicate there has been a continuing release of pet snakes over time into the park.

And that might be good news for python-free areas. It would suggest that it might take the release of a somewhat large number of snakes before a stable wild population exists that can reproduce.

Hart’s team is also analyzing snippets of snake tails for pollution studies. Mercury is a toxic element that can poison animals, including people. It’s given off by coal-fired power plants and other facilities. Often it moves through aquatic environments, tainting fish, the birds that eat fish, and other animals.

By studying tissue from snake tails, Hart’s team has found that pythons can have high concentrations of mercury. If the baby snakes in P-52’s eggs are well developed enough, the biologists will look to see whether mom passed any of that mercury on to her young.

And about those eggs: Scientists at the Florida Museum of Natural History retrieved huge handfuls from the record-breaking python. “There are not many records of how many eggs a large female snake carries in the wild,” says Everglades National Park biologist Skip Snow. The load in P-52 “shows they’re a really reproductive animal,” he says, “which aids in their invasiveness.”

After studies of P-52 are completed, her body will be mounted and showcased at the museum for five years. Later, it will be returned to Everglades National Park. There it will serve as a potent symbol of the impact of just one introduced species in a wild environment.

This video starts with still images of USGS researchers using a radio tracker to hunt for P-46 in March. Researchers then find a python hidden in saw grass, which leads to the initial capture of record-breaking P-52. A video records her capture again in April, the final time, as she’s readied to be permanently removed from the wild. Credit: C. Puckett/USGS

 

Power Words

accelerometer An instrument for measuring vibrations or a change in the rate of movement. The one being used with snakes can measure movement changes in all three dimensions.

cryptic Having a behavior that is mysterious or possessing the ability to hide by concealing itself within the surrounding environment.

ecosystem The natural community of plants, animals and microorganisms that evolved to live together in a particular place with a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra.

freshwater Water that is not salty, such as rain, rivers and lake water.

GPS device GPS is short for Global Positioning System. This system uses devices that calculate their position (in terms of latitude and longitude) from any place on the ground or in the air. They do this by comparing how long it takes signals from different satellites to reach them.

habitat The natural environment in which a plant or animal normally lives. This includes not only the structural environment (such as sand, soil, rock or water) but also the other organisms that share that ecosystem.

herpetologist A biologist who studies reptiles and amphibians.

metabolism The chemical processes by which cells use energy and nutrients to make the substances that sustain life.

predator An animal that must capture and feed on other animals to survive.

radio tracking Following the movements of an animal or object using a device that gives off radio waves. A receiver can pick up those radio-frequency waves to provide information on how far away the broadcasting signal is and in which direction. Many biologists implant devices that broadcast such radio-wave signals to keep track of animals in the wild.

reptile Cold-blooded vertebrate animals, whose skin is covered with scales or horny plates. Snakes, turtles, lizards and alligators are all reptiles.

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