It’s well known that opossums are essential to an ecosystem: they feed on ticks, cockroaches, rats, slugs, small venomous snakes (they are immune to their venom), and other unwanted pests. They also eat the carcasses of dead animals. They are nature’s cleaners.
Jeremy Dixon, director of the Crocodile Lake National Wildlife Refuge, Michael Cove of the North Carolina Museum of Natural Sciences, and A.J. Sanjar, a student at Southern Illinois University, have recently discovered another talent they possess: they can help pinpoint the location of Burmese pythons… by getting eaten by them.
In Key Largo, the Burmese python, an invasive species, is spreading rapidly because it finds a favorable environment there, consisting of thousands of crevices and caves where it takes refuge. This makes capturing it impossible when it is breeding or hiding from a tracking dog.
Sanjar and Cove realized that by placing a tracking collar on the opossums, the tracker continued to transmit even when the small mammal was eaten by a Burmese python.
However, as any Florida biologist will confirm, Burmese pythons are extremely harmful: they can grow to nearly six meters in length, and in their territories, the mammal population declines by 87 to 99%.
These predators were first spotted in 2007 on Key Largo. They were imported in the 1970s, 1980s, and 1990s through the exotic pet trade for private owners, before being released or escaping into the wild. The species has thrived in the Everglades and now extends as far as Fort Myers and Lake Okeechobee.
No animal cruelty
Far from being controversial, the method developed by Sanjar and Cove respects nature’s natural cycle: the opossums are captured in baited cages and then, fitted with a harness similar to that of a small dog, they are equipped with a simple collar. Finally, the scientists release them back into the wild exactly where they were captured, so they can recognize their territory and continue to forage. Some are eaten by pythons within two weeks, others within several months. Nature takes its natural course.
The opossum, a small white marsupial, is easier to fit with a collar than a skittish raccoon, as the latter would need to be sedated by a veterinarian, whereas the opossum cooperates more readily while remaining awake. Opossums are also more numerous and their territories are smaller, far from the mangroves they dislike, which makes hunting pythons easier.
An affordable solution
Tracking collars used to be satellite-connected and therefore expensive, costing up to $1,500.
But the new $190 collars, which do not track the opossum’s movements, activate only when the opossum remains motionless for six consecutive hours. This allows biologists to intervene and euthanize the pythons by easily locating them.
The best time to act is in the summer, when pythons are fattening up. Over the past two summers, biologists have captured 18 pythons using this method, all between 2.5 and 4 meters long—that is, adults of reproductive age, including females capable of laying between 30 and 60 eggs.
They now hope that their technique will be recognized, alongside others, by the South Florida Water Management District and used in the Everglades, where pythons are on the rise.
