These 5 National Park Residents Are Straight Out Of A Horror Movie

It’s officially spooky season, and with it comes the requisite onslaught of ghouls, ghosts and goblins. While these supernatural delights may provide a yearly thrill every October, there are earthly oddities far stranger than fiction living in just about every national park.

As someone who spent the entirety of 2020 traveling to every U.S. national park and writing about them for Outside Online, I’ve heard my fair share of real-world horror stories that take place inside our public lands. The ones that stood out the most to me? The terrifying tales of creepy crawly critters inhabiting some of the most popular national parks. In honor of Halloween, here are a few of the ghastliest creatures that keep me up at night.

Bot Flies and Warbles: Denali, Kobuk Valley, and Gates of the Arctic national parks, Alaska

Though the name might sound cute, warbles are the larvae of bot and warble flies which lay their eggs in birds and mammals—including humans. Every summer, one particular species of bot fly, Hypoderma tarandi, parasitize the leg and lower body hairs of caribou. The parasitic behavior doesn’t stop there. Throughout the late summer and fall, these eggs hatch, and the larvae dig through the host’s skin, slowly crawling up its insides and feasting on its flesh until they reach its backside, typically in early summer. Then, like something out of Saw, the warbles emerge from a series of holes in the caribou’s back, falling to the ground to pupate. Adult warble flies don’t even live long enough to have mouth parts for feeding. Hunters have reported finding hundreds of scar marks on skinned cervid hides from massive warble infestations.

As if that wasn’t bad enough, Alaska’s caribou are also besieged by nasal bot flies, which deposit larvae directly into their nostrils. These larvae then crawl back into the animal’s throat, where they spend the winter. In severe cases, over 50 larvae can wriggle around a single caribou’s throat passageway, which causes breathing difficulties and even suffocation. The adult flies emerge in the spring, flying out from the poor caribou’s nostrils only to torment them again in the fall, when it’s time for the flies to mate. Groups of panic-stricken caribou are known to gather together when under attack, snorting and sneezing and even stampeding to get away from a swarm of nasal bot flies. In Denali, it’s not uncommon to see a crazed caribou sprinting across the tundra in early autumn, shaking its head and twitching as if possessed. 

Brazilian Free-Tailed Bat: Carlsbad Caverns National Park, New Mexico

Though they’re less horrifying than Alaska’s bot flies, Carlsbad Caverns’ most famous residents, the Brazilian Free-Tailed Bats, are certainly creepy looking, with translucent wings and little squished pig noses. Sure, they’re tiny, weighing-in at a scant .5 ounces, but during their spring and fall migrations, their population inside the park’s cave can reach a staggering 793,000 individuals.

From May through October, visitors to the park have the opportunity to gather at the amphitheater near the Natural Entrance to witness hundreds of thousands of the flying mammals emerge from their dark roost like Dementors in the Harry Potter series. It’s said that during these flights, visitors can even catch a whiff of the bats’ acrid odor. Thankfully, the bats are a huge positive for the surrounding environment. As a whole, the colony eats an estimated 4,000 to 6,000 pounds of insects each night, mostly pests that damage the nearby alfalfa and cotton crops. In this way, the tiny spooksters are an incredibly effective (and all natural) pesticide.

It’s not Halloween without bats. However, many bats in other U.S. parks are currently losing their lives to an even scarier pest, white-nose syndrome. If you’d like to help protect bat populations, check out Carlsbad’s Adopt-A-Bat program.

Leeches: Rocky Mountain, Grand Teton, and Olympic national parks, to name a few

After years of miraculously avoiding them, leeches finally caught up to me as I soaked my tired feet in Rocky Mountain’s Lily Lake last summer. I emerged from the water to find several tiny, squiggly worms attached to my legs that I immediately brushed off, shocked at how difficult it was to get the tiny suckers to un-stick.

These strange invertebrates occupy nearly every water source in Grand Teton and nearby Jackson Hole, too. They swim on their own or latch onto the bodies of tourists and local amphibians with their gruesome jaws and scores of teeth. Think you’re safe farther north? Think again. These ick-inducing annelids are present in popular lakes in Olympic (Lake Crescent) and Isle Royale (Chickenbone Lake), too.

The good news? Leeches are not known to carry any human diseases. Though they might make your stomach crawl, these critters are far less dangerous than an ordinary mosquito.

Wood Frog: Gates of the Arctic National Park and Preserve, Alaska

I first heard about the wonder of wood frogs from National Geographic’s America’s National Parks series, utterly fascinated that they are the only frogs known to live north of the Arctic Circle. The way they pull it off, though, is mind-boggling.

Unlike many animals, which hibernate or migrate to escape the harsh winter, wood frogs become frozen alive for up to eight months each year. First, the frog’s liver produces huge amounts of glucose that flush into every cell in its body, preventing ice from forming inside its cells. Next, ice fills its internal cavity, encasing its organs. Lastly, the frog’s heartbeat stops completely, and there is no breathing or muscle movement until the spring thaw arrives.

By withstanding being literally frozen alive, wood frogs endure conditions that would be deadly for nearly all other animals.

Bleeding Tooth Fungus: Across North America, from Denali to Acadia

The next time you’re hiking and you see a white blob that looks like it’s oozing out strawberry jelly, it’s best not to put it in your mouth. The culprit is likely the “bleeding tooth” or “devil’s tooth” fungus, which produces a blood-like secretion through a process known as guttation. Trypophobes and hemophobes beware: When this fungus has absorbed water too quickly, it can seep out through small surface openings, and, in this case, bleed red droplets like a fresh wound. Though rare, the fruiting bodies of these strange fungi live in dense, coniferous forests in mountainous areas.

Though the bleeding tooth fungus is not toxic, some say it tastes pretty nasty. The National Park Service recently stated on its social media that it tastes like “bitterness and regret.” So, maybe stick to the chanterelles.