It was a warm summer morning and shirtless, sweaty runners were just coming off the Wissahickon Trail. As they ascended out of the picturesque valley in Northwest Philadelphia to start the workday, a woman named Mary and two companions were heading the other direction, already getting down to business.
Their mission looked a little like a low-budget “Indiana Jones” flick. Stopping part way down a trail, Mary, the leader, handed a younger woman a pair of bright white hard-boiled eggs, which she carried gingerly up a steep craggy embankment where a huge concrete bridge loomed overhead. She lost her footing once or twice, prompting calls of caution from below, before nearing the apex and underhand tossing one of the eggs a few feet to her side. It plopped, rolled and threatened to run all the way back down before settling somewhere in the middle.
All around the embankment were signs of the target of the operation: the little paw prints and scat of Vulpes vulpes, the red fox. Days earlier, one suffering from mange had been spotted near the top of the slope. Mary and her friends hoped that the eggs, medicated with the antiparasitic drug ivermectin, would spare it from a potentially slow, scratchy, agonizing death.
Just one problem: their efforts could be entirely ineffective or even harmful, wildlife experts caution. They’re also illegal.
Welcome to Northwest Philly fox fight.
For more than a year now, Mary, whose full identity Grid is concealing due to the sensitivity of the subject, has been on a personal mission to combat what she says is rampant mange among area foxes, primarily in Mount Airy, but also stretching into surrounding neighborhoods. She first got the notion about five years ago, when she and her son noticed that a fox that regularly visited their yard in West Mount Airy suddenly had no fur midway down its body to the tip of its tail, and was just “scratching and scratching and scratching,” she says.
Mary, who has no professional background in wildlife management or medicine, took to Google and researched protocols she says are espoused by some wildlife experts and government entities on how to help foxes suffering from mange, a disease caused by microscopic mites that bury into the skin of some mammalian species. First, she began attracting the fox to her yard by putting food out at the same time each day. Then, she began slipping in doses of ivermectin over the course of several weeks.
“About four weeks later, our fox came back, and we could see that her fur was growing in on the back half of her body… and she came with a baby [kit],” Mary says. “That was it. We were in love with this little furball bounding around in our yard, and it was the best feeling ever that we helped this mama fox and her baby.”
Mary says after the success, she stopped putting out food so as not to further acclimate the fox to human interactions. But really she was just getting started. In fall of 2023, Mary says she began to notice a high number of other mangy foxes in the area, bolstered by social media postings shared by others.
It look[ed] like the apocalypse out there. They’re just missing all their fur, they were thin … people were seeing hairless foxes on their lawn, just curled up and dead. It was heartbreaking.”
— Mary, Mount Airy resident
“I saw other people posting, sometimes with photos that were really distressing,” Mary says. “It look[ed] like the apocalypse out there. They’re just missing all their fur, they were thin … people were seeing hairless foxes on their lawn, just curled up and dead. It was heartbreaking.”
Mary purchased more ivermectin off the internet and began “napalming” the area, leaving treated eggs at sites known to be frequented by foxes. As that effort wound down, she transitioned to a one-to-one approach, contacting people who posted on social media asking for help, delivering them medicated eggs and explaining her method to treat their own backyard foxes. That effort continues.
“The endgame for me is to not create dependence between foxes and humans,” Mary says. “It’s just such a simple thing to try to treat them. Why wouldn’t we, right?”
Well, for lots of reasons, says Andrew Di Salvo, wildlife veterinarian at the Pennsylvania Game Commission. First and foremost, Di Salvo and his counterparts at the commission say state statutes make it illegal for anyone without a proper license to attempt to medicate wildlife. Those statutes are backed up by science-based wildlife management practices that identify dangers and drawbacks in medicating wildlife, he says.
“It is inherently dangerous and irresponsible just to throw bait out on the landscape that has a drug,” Di Salvo says.
It’s a whole mess that is created from what seems like a very innocuous [instinct] … to give wildlife every chance they can to recover, when it has all these potential downstream impacts.”
— Andrew Di Salvo, Pennsylvania Game Commission
Di Salvo says he understands why people would have such concerns for wildlife. Mange outbreaks can decimate local fox populations, according to the commission’s own website. The manner of death is brutal: all that scratching limits the ability to sleep and hunt, starving and weakening the animal for months until death arrives. Secondary infections from breaking the skin while scratching or exposure to the cold from fur loss can contribute to more acute deaths.
Di Salvo says the state keeps a “robust” monitoring network that can help identify when outbreaks are occurring for a variety of ailments in different species. Although he did not say whether the commission has identified any mange outbreaks in fox populations in Northwest Philadelphia, he says statewide, there’s “no indication yet” that red fox populations are threatened by mange in any corner of the state.
But that’s besides the point, he adds. Even if an outbreak is occurring, there is little to suggest some form of intervention would do more good than harm.
“The problem is, from a management perspective, what can we do?” Di Salvo says.
The commission used to have a program that treated black bears for mange with ivermectin, he says. But they stopped in 2022 after a Penn State University study found that about 80% of bears with mild to moderate mange recovered whether or not they were treated. The study did find slightly better rates of recovery for bears with severe cases, but mortality was still high either way, leading to a new policy of euthanizing bears found in such acute conditions.
Di Salvo says the takeaway of the study was that risks of treatment far outweigh the rewards. In worst-case scenarios, ivermectin-treated eggs left on the landscape could be eaten by the wrong species, with potentially dangerous consequences. (Ivermectin can be deadly to collies and similar dog breeds due to a genetic vulnerability. Indeed, Mary has also received criticism from some Mount Airy dog owners.) Foxes are also a rabies vector, leading to a risk to humans if they are conditioned to frequent backyards.
But there are less obvious risks, too, Di Salvo says. Indiscriminate use of medication like ivermectin could start to breed resistance among mite species and limit natural selection’s ability to produce more capable fox populations. He says there is also evidence that ivermectin can appear to be working but actually interfere with a fox’s immune system, leaving it vulnerable to a super-charged rebound of mange.
But there is little to suggest Mary and those seeking her assistance locally are convinced. In a world seemingly filled with bad news near and far, she holds her efforts up as one of the few good things she feels sure of.
“There’s so much that you can’t do about all this horror everywhere,” Mary says. “But this is such a fixable problem. It’s so easy.”
She says she has grown more cautious in her approach, placing eggs more infrequently and in more off-the-beaten-track locations to limit the risk of overdosing, or that a dog might stumble upon it. She feels bolstered by interactions with wildlife centers that she says lended their expertise and even support in treating the foxes. Mary even claims that one area center dosed her first batch of eggs with ivermectin; a claim the center denied in correspondence with Grid, adding that they agreed with the policy of the Game Commission.
Di Salvo responds that he has yet to see a convincing, science-backed argument from any wildlife management agency that the benefits of treating foxes with mange outweighs the risks.
“It’s a whole mess that is created from what seems like a very innocuous [instinct],” he says. “To give wildlife every chance they can to recover, when it has all these potential downstream impacts.”
