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KEN PERROTTE: Censors playing possum when it comes to online wildlife myths

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An opossum.

DON’T YOU love it when Facebook slaps unwanted censorship on a post or “independent fact checkers” flagging caveat people’s comments? Yeah, me too.

So far, the fact checkers are AWOL in correcting the facts associated with memes and themes posted by animal rights activists and organizations. Take, for example, the myth about opossums and ticks.

Pervasive memes posted on social media in recent years assert that cute, cuddly opossums, those native marsupials with beady eyes, sharp teeth, large naked ears and a long prehensile tail, are an angelic species when it comes to eradicating disease-spreading ticks.

The memes assert legendary effects, such as a single opossum kills more than 5,000 ticks a year. Promoted on countless sites – even some affiliated with the outdoors—is the theme that opossums are saving humans from Lyme Disease and other tick-borne diseases.

The bigger trouble – pay attention, fact checkers – is this whole opossum-tick notion seems to be a crock.

This was finally evidenced by a study last year, a peer-reviewed report published in September 2021 in “Tick and Tick Borne Diseases.” The report, by Dr. Cecilia Hennessy and Kaitlyn Hild of Eureka College’s Division of Science and Mathematics, is titled “Are Virginia opossums really ecological traps for ticks? Groundtruthing laboratory operations.”

Myth Origins

Six captive opossums were used in a study reported in the August 2009 Proceedings of the Royal Society B journal. Researchers in New York placed captured species of small mammals and birds (white-footed mice, chipmunks, gray squirrels, opossums, catbirds and veeries) into cages and then “inoculated” them on their heads and necks with 100 larval ticks.

For four days – the amount of time researchers deemed sufficient for a tick to gorge and drop off a host—they counted how many ticks fell from the cages into a collection pan. Any ticks not accounted for directly were assumed to have been eaten or destroyed as the animals groomed themselves.

Squirrels and opossums seemed to rid themselves of the most ticks, allegedly killing 83–96.5 percent of them, with opossums at the high end of the scale. This was extrapolated out to the assertion that opossums can vacuum up to 5,500 ticks each season, making them an “ecological trap” for ticks and a “net reducer” of the parasites.

The Latest Science

Hennessey and Hild poked holes in the 2009 researchers’ assumptions. They analyzed stomach contents of 32 wild Virginia opossums from central Illinois, using a dissecting microscope to painstakingly look for ticks or tick body parts in the opossums’ stomachs. They found absolutely no evidence of ticks.

They also reviewed all the science (23 papers in all) on opossum foraging, stomach contents and scat and found none that presented any evidence of ticks in opossum stomachs.

Dr. Bret Collier, associate professor of wildlife ecology at Louisiana State University’s School of Renewable Natural Resources, closely follows such research and finds this study definitive.

“Ticks are not, in any manner, selected for by Virginia opossums,” he said, meaning opossums don’t go out and actively target ticks as a food source. “I think we can, and should, put this meme and idea to rest.”

So, where did the ticks go in the 2009 study?

Hennessy and Hild note that the 2009 researchers assumed animal grooming behavior must have occurred in the lab because larval ticks weren’t collected in the cage se-up. They questioned, though, whether four days were long enough for larval ticks to feed and drop off. Some laboratory studies showed feeding can last up to 10 days.

According to Hennessey and Hild, the 2009 researchers didn’t check the opossums for ticks before releasing them from captivity; the assumption was any tick still alive would have fed and dropped to the tray beneath the animals. “It is possible that ticks could have still been embedded and feeding on the opossums upon release,” reads the report.

The 2021 study report skewers memes and myths that go viral and are later debunked, noting they “undermine the public trust in experts and evidence-based science.”

The 2021 researchers found ample evidence of people trying to attract opossums to their yards to serve as tick traps, declaring this a bad idea that increases exposure to zoonotic diseases the animals can carry.

“This body of memes turned out to be an extremely successful advocacy campaign for the opossum; allowing the oft-maligned scavenger to achieve cult status as a biocontrol for ticks. Unfortunately, these purported benefits are not supported by our findings or by previous diet analyses,” the report concludes.

So, let’s await the fact-checkers. Still waiting…

Opossums and Turkeys

Collier is one of the country’s foremost researchers of wild turkey ecology. He took this tick-enlightening moment to also address misconceptions related to opossums and wild turkeys. Some turkey hunters like to paint opossums as voracious predators of ground-nesting hens and their eggs.

“In my experience, opossums do not push females off nests; they usually roll in after something has eaten the female and maybe snag or scavenge an egg, but they are certainly not primary predators of turkey nests and turkeys are not at all scared of them,” Collier said. “I ascribe little to no actual nest predation to opossums; it’s scavenging.”

So, as Collier notes, opossums don’t impact tick populations and, likely, aren’t big players when it comes to destroying turkey nests. Turkeys, young and old, eat ticks.

When you consider it, though, ticks aren’t much of a meal for anything, relative to the work required compared to other food sources animals and birds seek. It really comes down to a cost-benefit situation, finding food delivering optimal caloric intake with minimal caloric expenditure.

I don’t know how you make a meme out of that.

For more wide-ranging outdoors coverage, including hunting, fishing wild game recipes and more, see Ken Perrotte’s weblog.

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