Pythons tracked by possums eaten with GPS collars

FORT LAUDERDALE, Florida. Wildlife researchers studying mammals in Key Largo have discovered a potentially groundbreaking — if not heartbreaking — way to locate and kill invasive Burmese pythons, especially large ones.

A team monitoring the behavior of raccoons and opossums in cities and on the outskirts of the Crocodile National Wildlife Refuge put dozens of mammals on GPS collars and tracked their whereabouts for several months.

In September, about five months after the start of the study, one of the collared opossums signaled death, caused by a lack of movement—possibly hit by a car or killed by a local dog. But then, a few hours later, the collar started moving again.

The researchers had a premonition that the opossum suffered a cruel fate.

“This is a tell-tale sign that they have been eaten by a snake,” said Michael Kove, curator of mammals at the North Carolina Museum of Natural Sciences, one of the study’s partners. He and his research partners at the U.S. Fish and Wildlife Service and Southern Illinois University suspected that the snake was sitting and digesting the opossum and then moving again.

But even with a tracker, it will take time to confirm their hunch – Key Largo is, in fact, a giant petrified coral reef with a labyrinth of underground pockets and caves. “This thing was underground. It took a month to track down the snake underground (to catch it).”

When they finally pulled him out of the ground, they found a 12-foot-long, 66-pound female full of egg follicles. Such large females can lay about 100 eggs and are the holy grail for python hunters. Removing them from an ecosystem is like removing dozens if not hundreds of future snakes. The team put her to sleep, cut her open and removed the collar they hope to put on another opossum soon.

While the opossum’s demise was grim – pythons coil around their prey, squeezing it each time the animal exhales and eventually suffocate it – the death proved that wildlife can find large pythons by stalking their prey.

Cove and his research partners hope this method will help control the explosive population growth of the invasive snake that has decimated South Florida’s ecosystems for decades. Native to Southeast Asia, Burmese pythons likely made their way into the Everglades in the 1990s through the exotic pet trade.

They thrived, creating breeding populations as far south as Key Largo and as far north as the Loxahatchee National Wildlife Refuge in western Palm Beach County.

Cove said the problem in Everglades National Park is so severe that “there are no more mammals to put these collars on.” Largest invasive python ever recorded in Florida was 18 feet long.

Proof of concept and glitch

The study was conducted on the borderline between the human world and the wild and looked at what happens when raccoons and opossums “dive into trash cans and eat all the cat food people have prepared for them instead of eating local seeds and fruits.” Cove said. .

Both species consume a lot of local fruits and defecate seeds in different places, becoming important seed dispersers.

However, a parallel goal was to learn more about pythons if the mammals were eaten.

“If we could catch the snake at the scene of the crime, that could lead to the management and removal of the pythons,” Kove said.

The first opossum was a proof of concept – the collar survived being crushed by the snake, and the snake did not go through the collar, giving scientists time to find it.

Two weeks ago, the second collar stopped moving and then started moving again, indicating that the big raccoon had been eaten by a snake. This time they found the snake faster: Jackpot, a 77-pound hippo also full of egg follicles.

On Wednesday, another collar gave a death signal and started moving again. But by the time the researchers got to the tracker, they found only the collar in a pile of snake feces. The python, apparently massive enough to fit through the device, was still there.

“I was very disappointed that we didn’t get the giant snake monster that ate that last opossum,” Cove said. They now know that there is a sense of urgency, especially if the snake is large enough to fit through the collar.

Of the 43 collars they used, three are known to have been swallowed by pythons, but another six simply disappeared. The research team is now wondering if they were eaten by pythons, which then moved out of the geographic range of the study.

Cruel or decisive?

Is tracking prey for pythons the same as using innocent raccoons and opossums as bait?

“That’s the question we get – don’t you feel guilty about putting these animals at risk?” Cove said.

He said that collared animals are not at greater risk – they go about their business as usual, and the researchers make sure that the collars do not interfere with their movements. Unfortunately, pythons sometimes intercept them.

“We do nothing but watch the animals go about their natural business and unfortunately they get eaten and that ends up killing the pythons,” he said.

Currently, no one has invented an effective way to remove invasive pythons.

Authorities have tried many methods, including tracking them with hounds, hosting a python catching derby called the Python Challenge — last year’s 10-day competition resulted in the deaths of 231 snakes, a fraction of “tens of thousands,” the USGS estimates. . hiding in the wild.