Research suggests alligators, a sentinel species for PFAS impacts, are losing their superhuman healing abilities
Matthew Guillette wears a baseball cap and crocodile skin-patterned camo pants as he peers across the water on Bald Head Island. His keen eyes skim the water’s edge on the far bank, and catches sight of crocodiles faster than anyone else can.
Catching the apex predators is in Guillette’s blood. You might even say alligator blood is in his blood, since he’s adept at drawing it for research purposes. His father, Louis Guillette, was a renowned biologist and ecotoxicologist, who won the 2011 Heinz Award for the environment.
“I grew up doing this ecotoxicology on gators,” Guillette said. “Now that he's passed on, I'm trying to carry the torch with a new team and I'm very proud of the work we've been doing.”
That work is focused on forever chemicals: per- and poly-fluoroalkyl substances (PFAS). They’re known for their water and oil repellant qualities and are used in countless consumer products, from non-stick cookware to cosmetics, food packaging, and furniture.
There are thousands of them, and hundreds have been found contaminating the Cape Fear River. Most do not degrade in the natural environment and have been linked to adverse health effects in humans, including developmental problems, cancer, liver and thyroid problems, and immune effects.
That last category — immune effects — has been found in other species as well. Including alligators, thanks to Guillette and his research team.
To study the effects of PFAS on human health, it’s helpful to compare other species in the region to humans. And in the case of the Wilmington region, there’s a notably higher amount of PFAS in the blood of alligators living near the Cape Fear River and its watershed than in nearby Lake Waccamaw.
According to Guillette’s study, currently under peer review, the composition of PFAS in the blood of alligators in Greenfield Lake in Wilmington is “in general agreement with those found in the blood of adults and children exposed to PFAS from drinking water in Wilmington, NC.”
That data comes from alligator captures in 2018-2019, just a year or two after the GenX contamination in the Cape Fear River came to light. Alligators are an ideal species to study the health impacts of environmental toxins for a few reasons: They’re long-lived, surviving for 30 to 50 years in the wild; they’re adept at healing; and they’re continuously exposed to contaminants in human drinking water sources, like rivers.
One of the other researchers, NCSU biologist Scott Belcher, said the gators with high PFAS levels seemed to have health problems.
“We believe we're seeing actual changes in the immune function of the alligators, especially the ones that Greenfield Lake,” Belcher said. “We're seeing a number of unhealed wounds, which is very atypical for alligators, as well as a lot of changes in the immune cells and the immune function in those alligators.”
Biologist Scott Belcher has found a correlation between PFAS content in the blood and slow healing abilities in gators. Their immune functions seem inhibited, and similar to autoimmune disorders in humans. 4/5 pic.twitter.com/wkiDvLPoSE— Kelly Kenoyer (@Kelly_Kenoyer) April 14, 2022
American alligators have blood serum which is uniquely good at
taking out bacteria and viruses
. Their blood coagulates quickly and fights off infections with ease. It’s a necessary adaptation for the alligator, which often engages in territorial fights with its rivals in mucky rivers and ponds full of pathogens.
But despite those healing abilities, 20% of the alligators in Greenfield Lake in Wilmington showed evidence of slow healing, skin lesions, and infected wounds. These painful-looking lesions show fungal growth, in many cases, and are sometimes called “fuzzy wounds.”
These problems didn’t come up for alligators in nearby Lake Waccamaw, which is not contaminated with nearly as much PFAS.
Cape Fear alligators also had blood that coagulated more slowly, and an analysis of their genetic expression indicated similarities to human autoimmune disorders, including Lupus.
They're capturing alligators to draw blood and other samples, and also checking them over for unhealed injuries, like this one, which shows signs of infection or fungal growth. These wounds are unusual on gators, because they typically heal very quickly from injury. 2/5 pic.twitter.com/uQrTpMonz4— Kelly Kenoyer (@Kelly_Kenoyer) April 14, 2022
One alligator with particularly high PFAS levels in that study came from Bald Head Island, which sits like a cap at the end of the Cape Fear River. The Bald Head Island Conservancy is a partner in the study, and chief scientist Beth Darrow said the ponds and lakes on the island mostly are fed from groundwater. That’s why she was surprised by that specimen’s high PFAS concentration.
“It's possible that individual didn't actually come from Bald Head Island. It could have come from elsewhere in the Cape Fear River,” she said.
That’s why this newer study involves tracking devices. “We’re putting some satellite transponders on some of them to look at their movement patterns. So we'll know more about how far they go, and whether they're native to here and stay here, or moved throughout the watershed.”
Only the largest alligators are suitable for tracking devices, and catching them is no small feat.
People often mistake Belcher, Guillette, and Kylie Rock (their post-doc colleague) for regular fishermen. The equipment for catching an alligator can look similar: large fishing nets and heavy duty fishing poles, plus coolers — not for fish, but to keep the blood samples at a safe temperature for study.
But a few elements stand out — the dog-catcher pole, for one. It’s a pole with a loop of steel cable at the end, which can be pulled tight around an alligator’s neck.
After spotting an alligator, Belcher and Guillette would ready their fishing poles. They carry no bait but had large, unbarbed hooks at the end meant to grab the gator’s armored hide.
Alligators like to stay near the bank, often hidden under brush and branches. These obstacles stop any fishing line, so the biologists have to draw them out.
Belcher carries a Bluetooth speaker, and plays a high-pitched chirping noise from it. It’s a recording of a baby alligator calling out, Darrow said, as she watches from a careful distance. “For the females that will attract them because they have the instinct to go protect the baby,” she explains, “and the males, that's more of an aggressive behavior. But it tends to work on both.”
Male alligators are easier to catch because they’re less cautious and will continue to be attracted by the lure, even after a cast nearly nabs them. The females, by comparison, aren’t fooled as easily, and won’t come out a second time after a failed cast.
Once the animal is in the open, the team snags it with a reel or two, depending on size, and reels it in. Then a dog-catching pole is used to loop around its neck, and the creature is dragged onshore.
Belcher and Guillette take turns doing the next part- stepping over the gator from the side, then pressing its top jaw to the ground to close its mouth. Others will come put their weight on the animal if it’s too large for one person to control, while tape is put around the animal's mouth for safety.
How to safely disarm an alligator. Kids, don't try this at home. pic.twitter.com/QJKYiua1QV— Kelly Kenoyer (@Kelly_Kenoyer) April 15, 2022
Duct tape or even a human hand can hold the jaw shut — while the animals can bite down with incredible force, the muscles that open their jaws are quite weak.
Guillette and Belcher manage to catch one alligator that simply can’t learn its lesson after multiple missed casts. Before they even get to check its sex, they make a guess: this one is probably a male.
“Boys are not the smartest,” Belcher explained to a family watching the capture from nearby.
The process of catching them is intense! But very cool. Here's scientist Matthew Guillette expertly catching an 8.5 foot alligator. 3/5 pic.twitter.com/PJj6Y27OQH— Kelly Kenoyer (@Kelly_Kenoyer) April 14, 2022
He views these outings as a good opportunity for outreach to the community, and one capture near a road draws a small crowd of observers.
Guillette takes measurements on the male gator while one of SBI Conservancy’s interns sits on the animal to keep it still.
“Do you want to feel one of the paws? They’re really soft,” Guillette asks one of the children. Several take him up on the opportunity to touch the animal, although none are brave enough to touch his feet.
Alligators have tough-yet-flexible armor on top, but underneath, their bellies are quite soft. Their feet in particular are incredibly soft, even with claws that look ready to dig or mangle.
As they apply the gator’s orange face “make-up” before release, and Belcher again explains the process to curious onlookers.
“We use the same thing that they use to identify cattle. So it's a cattle marker and it's just kind of a little colored wax,” Belcher said. “So if we're out working again, we won't try to catch it again.”
Belcher also takes the opportunity to explain a bit about PFAS exposure to the observers.
“They’re forever chemicals, they're a type of chemical contaminant that's not regulated. And that has been a big problem in the Cape Fear River,” Belcher said. “The first contamination that was really bad from the manufacturer of Teflon was in Parkersburg, West Virginia.”
He tells the observers about his research, how the PFAS exposure shows similar negative health effects in alligators as it does in humans: “This is our fifth season that we're kicking off and we're almost to 300 captures that we've had in the last five years.”
But the observers aren’t as keen on the PFAS angle, so he doesn’t get to the point outlined in the last line of his study in peer review: that the adverse immune effects in alligators are similar to human populations, reaffirming “the need to reduce exposure and cease production and use of a chemical class that, through its ubiquity and persistence, is a global environmental health concern.”
Still, Belcher hopes this kind of experience can instill excitement and wonder in the next generation of scientists.
“You like science?” He asks one little girl.
“You still want to do marine biology?” The mother asks, urging the little girl. And she nods, shyly.
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