I love a good monster story. Big, small, hairy, scaly, passive, aggressive (maybe even passive-aggressive..."I want to eat you, but I'm worried about cholesterol"), it doesn't matter. The things that lurk in the dark corners of your bedroom, just behind the tree line, or in the dank depths of the lake are eerily fun.

But, are monsters real?

Of course. Haven't you ever watched Sesame Street?

Throughout the centuries, people have reported encountering thousands of monsters across North America, some ridiculous (the Slide-Rock Bolter comes to mind, a land whale with a tail hooked to a mountain that releases the hook to slide over its prey) and some that make a whole lot of sense.

Let's look at the latter of those. Here are thirteen monsters that have, could, and may still exist in North America.

1. Bigfoot
Ook. Probably the most famous North American monster, Bigfoot has a centuries-spanning history, with some encounters hitting newspapers as early as the 18th century. Some noted historical figures knew of Bigfoot, including frontiersman Daniel Boone (who claimed to have killed a ten-foot-tall, hair-covered, two-legged "yahoo") and Teddy Roosevelet (a second-hand story of a Bigfoot appeared in his1893 book The Wilderness Hunter; the future president recounts the tale of a mountain man in Montana who encountered a huge, manlike, foul-smelling beast in the wild).

Bigfoot hit the news again in 1958, when a logger stumbled upon enormous, humanlike footprints in Northern California, but the hairy fella didn't fully capture the nation's attention until 1967 when Roger Patterson and Robert Gimlin filmed what appears to be a female Bigfoot near Bluff Creek, California.

Since that moment, Bigfoot has been in the American zeitgeist. Reports of the monster have come from forty-nine of the fifty United States, every Canadian province, throughout Mexico and Central America, and across every continent (except Antarctica. Maybe he goes there on vacation). The Bigfoot Field Researchers Organization has collected nearly 6,000 reports of Bigfoot sightings in the US since the 1990s.

But, what is it? An undiscovered North American ape? A remnant human ancestor, such as Neanderthal or Denisovan? An extant species of Gigantopithecus that migrated over the Bering Strait land bridge during the Pleistocene? Space alien?

2. North American Hyena
Yes, North America was once home to a species of hyena. The American Hyena, Chasmaporthetes ossifragus, lived across the continent between 4.9 million to 780,000 years ago before dying out.

Or did they?

In 1886, Montana rancher Israel Ammon Hutchins shot and killed a Shunka warak’in (translated from Ioway, it means "carries off dogs") that had been killing his livestock. The creature was wolf-like, but appeared more as a hyena than a canine. From 1900 to the present, there have been reports of people seeing individuals or packs of animals appearing to be hyenas from Texas; Idaho; New York; Massachusetts; Nebraska; Illinois; Pennsylvania; Iowa; California; and Alberta, Canada.

Is it possible populations of Chasmaporthetes ossifragus remain hidden from science? Of course. North America is covered with great swaths of under-explored forests, mountains, deserts, and tundra. An estimated forty-seven percent of the United States alone is unpopulated, and ninety-five percent is either unexplored or where man is a visitor. That number doesn't even count the wilds of Canada and Mexico. That leaves lots of territory open for the following other extinct, possibly extant, animals to thrive.

3. Thunderbird
Living between the Late Oligocene (33.9 million to 23 million years ago) to the Late Pleistocene (2.58 million to 11,700 years ago), the Teratorn was the monster of the sky. Its name, translated from Greek, means just that—monster bird. With a wingspan between eleven and twenty feet (the same as light utility aircraft), and a weight between thirty-three and 176 pounds (up to that of a grown man), their size rivaled a number of species of Pterodactyls from much earlier epochs.

And it may still exist in living, squawking form.

The Teratorn, related to modern-day New World vultures, was known to Native American and First Nations peoples as the Thunderbird. These birds were purported to create storms like, um, Storm from X-Men, and throw lightning bolts like, oh, I don't know, Zeus, or something.

Thunderbirds terrorized native peoples, and were known to carry off livestock, pets, and children.

Modern reports of these monster birds come from Massachusetts, New York, Pennsylvania, Virginia, Ohio, Texas, Montana, North Dakota, New Mexico, and Alaska.

From a February 1, 2018 story in Alaska's Juneau Empire, a number of people in the Mendenhall Valley reported witnessing a bird with a twenty-foot wingspan.

Eyewitness Tabitha Bauer told the newspaper, "The wingspan had to be at least twenty feet, it was almost as wide as the road. I have lived here all my life and have never seen anything like that, it freaked me out… This thing was HUGE, almost the size of a small airplane."

Although, according to science, the Teratorn is long extinct, these witnesses saw something in the sky too big to be there.

4 - 8. Water Monsters
There is no shortage of reports of water monsters in North America. These include Canada's Loch Ness Monster; Ogopogo, which inhabits Okanagan Lake, British Columbia, Canada; Lake Champlain's Champ of Vermont and New York; Cadborosaurus in the Pacific Northwest; and El Monstro ("the monster") from Isla de Malpelo, a Pacific island nearly 400 miles south of Panama. The deep, wet places on this Earth are prime locations for monsters. More than ninety percent of the ocean is unexplored; lakes and rivers aren't far behind.

Ogopogo: Okanagan Lake is 84 miles long, an average of 2.8 miles wide, and is 761 feet at its deepest. This is home to Ogopogo, Canada's most famous lake monster, which resembles the extinct sea mammal Basilosaurus (not a lizard, but a whale). First Nations peoples have known about this creature for hundreds of years, but white settlers first saw it in 1872.

Problems with Ogopogo being a surviving Basilosaurus include: 1) if it is indeed a surviving Basilosaurus, it's living in a freshwater lake, not the saltwater ocean in which it evolved, 2) it would need a breeding population to survive this long, 3) a Basilosaurus would need to breathe air, so sightings would be daily.

However, there have been more than 100 credible reports of Ogopogo since the 19th Century, with twenty of them occurring between 1981 and 2015. We don't know everything, folks.

Champ: Lake Champlain is more than twice the size of Okanagan Lake, although, at 400 feet, not as deep. Indigenous populations have reported a monster in this lake for centuries, and 1819 marked the first account from a white settler in the area. It had a head like a horse, which stuck about fifteen feet out of the water. The breeding population question is still an issue, but Lake Champlain is big, and over the past 200 years, more than 600 people have claimed to see the monster.

Cadborosaurus: Now, we're getting into something serious. Cadborosaurus supposedly has a horse-like head; large, front-facing eyes; and flippers on a body made of coils. First Nations peoples have stories about this creature from the distant past, recording its image in petroglyphs. Sailors along the North American Pacific Coast claimed sightings of this creature from 1791 to 1967, and, oh yeah, there's a PHOTOGRAPH of it taken by Richard Lawrence Pocock in British Columbia. Given the mysteries of the oceans, a creature like Cadborosaurus not existing would be curious.

El Monstro (The Monster): The uninhabited island Isla de Malpelo is known for its sharks, and is considered one of the best destinations for shark divers. That's why biologist Sandra Bessudo was diving in its waters when she saw a shark 160 feet down, and that shark shouldn't exist. The fifteen-foot-long, "shark-like" fish had huge eyes, and a dorsal fin in the wrong place. Experts have speculated the true identity of this huge creature to be a sand tiger shark, but this fish wasn't seen by some rube. El Monstro was witnessed by a scientist. I'll go with her account.

Gulf of Mexico Coelacanth: Four hundred ten million-year-old fossils of this lobe-finned fish have been known by science for hundreds of years. The fossil record ended 66 million years ago, but during the 1938 Christmas season, the scientific world received an unexpected present. A South African fishing boat caught a fish so strange the captain contacted South African naturalist Marjorie Courtenay-Latimer, who couldn't believe what she saw: a living creature from the time of the dinosaurs—a Coelacanth.

Other populations of Coelacanths have been found since then, off the coasts of Tanzania, Kenya, Mozambique, Madagascar, Comoros, and in Indonesia.

In 1949, a fisherman in the Gulf of Mexico sent to a scientist a scale from an odd fish he'd caught. The scientist determined the scale was from a Coelacanth.

Could the Coelacanth also live in the waters of the gulf? In the early 1990s, a silver 17th-century Spanish goblet featuring a Coelacanth, thought to have been forged in Mexico, was on display in the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. So, why not?

The sea holds more mysteries than we can fathom (see what I did there?).

9 and 10: The Saytoechin and the Cave Cow
Saytoechin, the "Beaver Eater," is a huge, hairy cryptid in Canada's Yukon Territory. First Nations peoples say that it's larger than a grizzly, and attacks beaver lodges to get to the beavers within. The creatures are more than ten feet tall, with a flat face and long tail, can stand on two legs, and has a hide that bullets won't penetrate.

Much farther south, in the Yucatán, people have reported encountering a Cave Cow, a huge, hairy cryptid, more than ten feet tall, with a flat face and long tail, that can stand on two legs, and has a hide that bullets won't penetrate.

Oh, and both the Saytoechin, and the Cave Cow have three-clawed "hands."

From the descriptions of these beasts, some cryptozoologists think they may be the giant ground sloth Megaloynx jeffersonii (native to North America), and the giant ground sloth Megatherium americanum (native to Central and South America). Yes, both these species became extinct 11,000 years ago, but if the descriptions fit…

11. Onza
The Onza, or Mexican Tiger, has long been known to the inhabitants of the rural parts of Mexico. Longer than a mountain lion, the Onza is said to be about three feet tall, eight feet long, and weighing around 220 pounds. It is said to have spots like a lynx.

However, since no specimens have been captured, the Onza is considered a myth, or a misidentification of the local wild cat jaguarondi, although the jaguarondi is less than half the purported size of the Onza.

According to Mexican history, the zoo of Montezuma II featured an Onza. The cat was also reported by the Spanish and Portuguese in the 16th century.

In the realm of possible cryptids, and unidentified big cat isn't a big reach. 12. Nayarit Ruffed Cat
Speaking of cats, hidden in the Sierra Madre Occidental mountains of the Mexican state Nayarit is another cryptid cat. Like the Ozna, the Nayarit Ruffed Cat is big, anywhere from four to seven feet long. It has long legs, large paws, and brown fur with a mane and stripes on its upper leg, and flanks.

And it has fangs. Big fangs. Saber-toothed-style fangs. And doesn't resemble any other cat species in the region.

Famed cryptozoologist Ivan Sanderson bought two pelts of what were said to be of the Ruffled Cat, although those pelts are lost to history.

Like the Onza, the Nayarit Ruffed Cat is currently unknown to science, although not to the mountain people of Nayarit.

13. Itzcuintlipotzotli
From mystery cats to mystery dogs.

Saying "Itzcuintlipotzotli" is a mouthful.

Mexico is home to the hairless dog breed Xoloitzcuintle (another mouthful); however, the west-central Mexican state Michoacán is home to a different breed of hairless dog, the Itzcuintlipotzotli. The Itzcuintlipotzotli is a terrier-sized canine with a humped back. The first time an account of Itzcuintlipotzotli appeared in print was in the 1780 book Ancient History of Mexico by Mexican priest Francisco Javier Clavijero, who said the dog was medium-sized, hairless, had no neck, had a head like a wolf, and possessed a bison-like hump.

Frances Calderon de la Barca, wife of the first Spanish minister to Mexico, reported seeing one in 1843, but credible modern reports are rare.

There are plenty more monsters in North America, both credible and incredible. These 12, along with more than 240 additional ones are discussed in my book, Chasing North American Monsters. Enjoy.