Zoologists put GPS tags on possums and raccoons to find invasive pythons
(Wikimedia Commons/Susan Jewell/USFWS https://bit.ly/3IyRRyU)
Zoologists from the US have come up with a new way to deal with invasive pythons that have taken over Florida and eaten most of the native mammals.
Usually these snakes hide in swamps and karst cavities, where they are difficult to find.
The researchers tagged possums and raccoons with a GPS-tagged collar, then when a python swallows the animal, the reptile can be found.
Field trials have confirmed the effectiveness of the strategy, and it is particularly well suited to finding large females, which are the main contributor to population growth.
Invasive snakes often become a serious environmental problem.
For example, the California king snakes (Lampropeltis californiae) hunt endemic lizards from the island of Gran Canaria so actively that their numbers are rapidly declining.
FLORIDA SNAKES
Florida's ecosystems are threatened by another invasive snake species.
In the 1990s, dark tiger pythons (Python bivittatus), which originate from Southeast Asia, settled in and around the Everglades National Park.
They began to prey on the small and medium-sized mammals living here and ate them almost completely in a few decades.
Also, the pythons have few predators, which allows them to multiply rapidly and grow to five meters or more.
Attempts to control the number of invader pythons by trapping and killing adults and destroying their nests have so far failed.
This is because these snakes are very secretive.
It is especially difficult to look for them in swamps and in areas with a large number of karst cavities.
Even the use of dogs trained to sniff out pythons did not help much in this task.
A team of zoologists from Southern Illinois University, the North Carolina Museum of Natural History and the US Fish and Wildlife Service have come up with an indigenous idea.
Last year, researchers launched a project to study Virginian opossums (Didelphis virginiana) and raccoons (Procyon lotor) in the Crocodile Lake Conservation Area.
They provided about 40 individuals with collars with GPS transmitters, and tracked their movements for several months.
Five months after the start of the study, one of the tagged opossums, judging by the readings of its sensor, stopped moving.
Scientists have suggested that the animal died as a victim of a dog or being under the wheels of a car.
However, a few hours later, the device again recorded slow movement. So it became clear to zoologists that the possum was swallowed by a python.
For several hours the snake lay in one place, digesting its prey, and then crawled away.
It took the researchers a month to confirm this hypothesis.
All this time they were looking for a python according to the indicators of the GPS sensor.
(Katie Hanson https://bit.ly/3YDONr5)
It was not an easy task, since the snake was hiding in the cavities of the petrified reef under the surface of the island.
When the reptile was finally taken out of the ground, it turned out that it was a huge female, about 3.5 meters long and weighing about 30 kilograms, with numerous follicles in the ovaries.
According to the team, such an individual can lay up to a hundred eggs at a time.
Removing it from the population ensures that several tens or even hundreds of young pythons will never be born.
The authors note that the main goal of their study was to understand how the propensity of raccoons and opossums to feed on human waste affects their ability to disperse plant seeds.
However, they also hoped to test whether invasive pythons could be tracked and captured if they ingested GPS-enabled prey.
(Welleby Veterinary Hospital/USGS https://bit.ly/3k6BhgG)
The possum case confirmed the concept's work.
It turned out that snakes actually swallow mammals with GPS sensors, and the sensors, in turn, work in the body of reptiles long enough for zoologists to find them.
A few weeks ago, researchers again found that the GPS-collared animal, this time a raccoon, had stopped moving and then resumed moving.
This indicated that the python had also eaten it. When the zoologists went to the place, they found a female snake weighing about 35 kilograms.
Soon another opossum fell prey to the python but this time its collar came out of the reptile with droppings before zoologists could get to it.
ETHICAL AND PRACTICAL
Scientists hope that the method they invented will help to deal more effectively with Florida pythons.
This is especially true with large females that hunt possums and raccoons and produce especially many offspring.
At the same time, collars do not make mammals more vulnerable to snakes, which makes this manual ethical in relation to native species.
In the near future, the researchers intend to continue the project and check if cheaper transmitters can be used to search for snakes.
However, zoologists admit that even the use of GPS tags is unlikely to completely destroy the population of invasive snakes.
In addition, in some parts of Florida, such as the Everglades, the snakes no longer have mammals large enough to hang transmitter collars on.
Sources:
- Crocodile Lake National Wildlife Refuge: https://www.fws.gov/refuge/crocodile-lake
- South Florida Sun-Sentinel: https://www.sun-sentinel.com/news/environment/fl-ne-opossum-python-tracking-20230211-5gkjwsyk75c3bejodovfmgp3ni-story.html
- Tampa Bay Times: https://www.tampabay.com/news/environment/2023/02/12/possums-with-gps-collars-offer-new-way-kill-florida-pythons/
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This is a really creative idea, but it seems to me that they're not going to find anywhere near enough snakes this way to control the population.
You have to tag the animal, hope it gets eaten by a snake, and then find the snake before the sensor stops working. My gut feeling is that it would take far too many people and too much money to reach the number of snakes that they need to reach for population control.
You mentioned this in the article,
but I just wanted to elaborate on that point.
Still, it is a very clever way to find the snakes for zoological study.
Yeah, I thought so too. They won't be able to attach thousands of gps trackers to thousands of poor raccoons, It's simply not scalable.
However, the data can provide patterns, and that's some useful info to work with.