10 Juicy Facts About Leeches

Ian Cook
Ian Cook

Leeches get a bad rap, but they’re actually pretty cool once you get to know them—and we're finding out more about them, even today. Recently, a team led by Anna Phillips, curator of parasitic worms at the Smithsonian National Museum of Natural History, discovered a new species of medicinal leech (pictured above) in a Maryland swamp. We asked parasite expert and curator at the American Museum of Natural History Mark E. Siddall to share some surprising facts about the worms we love to hate. 

1. Not all leeches suck blood.

Hematophagous, or blood-feeding, species are only one type of leech. “The vast majority of species are [hematophagous],” Siddall tells Mental Floss, “but it depends on the environment. In North America, there are probably more freshwater leeches that don’t feed on blood than there are blood-feeders.” And even among the hematophagous species, there are not too many who are after you. “Very few of them are interested in feeding on human blood,” Siddall says. “Certainly they’ll do it, if they’re given the opportunity, but they’re not what they’re spending most of their time feeding on.” 

2. Leeches are everywhere.

Japanese leech on a log
Pieria, Wikimedia Commons // Public Domain

“Every continent on the planet has leeches, with the exception of Antarctica,” Siddall says. “And even then there are marine leeches in Antarctic waters.” Humans have co-existed with leeches for so long, according to Siddall, that just about every language has a word for leech. 

3. Leeches have made a comeback in medicine.

Bloodletting for bloodletting’s sake has fallen out of favor with Western physicians, but that doesn’t mean medicinal leeches are enjoying a cushy retirement. Today, surgeons keep them on hand in the operating room and use them as mini-vacuums to clean up blood. “That is a perfectly sensible use of leeches,” Siddall says. Other uses, though, are less sensible: “The more naturopathic application of leeches in order to get rid of bad blood or to cure, I don’t know, whatever happens to ail you, is complete hooey,” he says. How on Earth would leeches take away bad blood and leave good blood? It’s silly.” 

4. Novelist Amy Tan has her own species of leeches.

Land-based leeches made an appearance in Tan’s 2005 book Saving Fish from Drowning, a fact that instantly put the author in leech researchers’ good graces. “There are not a lot of novels out there with terrestrial leeches in them,” Siddall says. So when he and his colleagues identified a new species of tiny terrestrial leeches, they gave the leech Tan’s name. The author loved it. “I am thrilled to be immortalized as Chtonobdella tanae,” Tan said in a press statement. “I am now planning my trip to Queensland, Australia, where I hope to take leisurely walks through the jungle, accompanied by a dozen or so of my namesake feeding on my ankles.”

5. Leeches can get pretty big.

The giant Amazon leech (Haementeria ghilianii) can grow up to 18 inches and live up to 20 years. And yes, this one’s a blood-feeder. Like all hematophagous species, H. ghilianii sticks its proboscis (which can be up to 6 inches long) into a host, drinks its fill, and falls off. Scientists thought the species was extinct until a zoologist found two specimens in the 1970s, one of whom he named Grandma Moses. We are not making this up.

6. Leeches make good bait.

Many walleye anglers swear by leeches. “A leech on any presentation moves more than other types of live bait," pro fisher Jerry Hein told Fishing League Worldwide. "I grew up fishing them, and I think they're the most effective live bait around no matter where you go." There’s an entire leech industry to provide fishers with their bait. One year, weather conditions kept the leeches from showing up in their typical habitats, which prevented their collection and sale. Speaking to CBS news, one tackle shop owner called the absence of leeches “the worst nightmare in the bait industry.”

7. Leech scientists use themselves as bait.

Siddall and his colleagues collect and study wild leeches. That means hours of trekking through leech territory, looking for specimens. “Whether we’re wandering in water or traipsing through a bamboo forest,” Siddall says, “we are relying on the fact that leeches are attracted to us.” Do the leeches feed on them? “Oh my god, yes. We try to get them before they feed on us … but sometimes, obviously, you can’t help it.”

8. Leech sex is mesmerizing.

Like many worms, leeches are all hermaphroditic. The specifics of mating vary by species, but most twine themselves together and trade sperm packets. (The two leeches in the video above are both named Norbert.)

9. Some leech species make surprisingly caring parents. 

“There’s a whole family of leeches that, when they lay their eggs, will cover them with their own bodies,” Siddall says. “They’ll lay the eggs, cover them with their bodies, and fan the eggs to prevent fungus or bacteria from getting on them, and then when the eggs hatch, they will attach to the parent. They’re not feeding on the parent, just hanging on, and then when the parent leech goes to its next blood meal it’s carrying its offspring to its next blood meal. That’s pretty profound parental care, especially for invertebrates.”

10. You might be the next to discover a new leech species. 

Despite living side-by-side with leeches for thousands of years, we’ve still got a lot to learn about them. Scientists are aware of about 700 different species, but they know there are many more out there. “I’ll tell you what I wish for,” Siddall says. “If you ever get fed on by a leech, rather than tearing off and burning it and throwing it in the trash, maybe observe it and see if you can see any color patterns. Understand that there’s a real possibility that it could be a new species. So watch them, let them finish. They’re not gonna take much blood. And who knows? It could be scientifically useful.”

9 Tiny Facts About the Chevrotain

Dave Curtis, Flickr // CC BY-NC-ND 2.0
Dave Curtis, Flickr // CC BY-NC-ND 2.0

With a round body, spindly legs, and long fangs, this odd creature gives the platypus a run for its money. Also known as the mouse deer, chevrotains are shy and mysterious, and not much is known about them. But here's what we do know.

1. Chevrotains are not mice, nor are they deer.

Lesser mouse deer or chevrotain
BirdHunter591/iStock via Getty Images

At first glance, these animals look like a weird mash-up of a deer, a mouse, and a pig. Mouse deer share a suborder with deer (Ruminantia) but are not considered “true deer.” They have their own family, Tragulidae.

2. Chevrotain species vary by weight.

Mouse deer in Thailand
MonthiraYodtiwong/iStock via Getty Images

These creatures are way smaller than any deer. Depending on the species, a chevrotain can weigh anywhere from 4 to 33 pounds. The smallest species is the lesser Malay, while the largest is the water chevrotain. No species gets any larger than a small dog.

3. There are a lot of different kinds of chevrotains.

Mouse deer
aee_werawan/iStock via Getty Images

This tiny animal comes in many variations. The family has been classified into two genera: true chevrotains (Hyemoschus) and the mouse deer (Tragulus). The spotted mouse deer are still very mysterious, so scientists have placed them in their own genus called Moschiola. Despite being categorized in different genera, they all share a similar look.

4. Chevrotain fangs are fiercer than Dracula's.

Chevrotain in a woodland
BirdHunter591/iStock via Getty Images

Open up a chevrotain’s mouth and you’ll find two long fangs. They're especially elongated in males, which use the needle-like canines to stab each other. Thanks to an extra thick coat and robust muscles around the neck and rump, these adorable fighters are protected from bites during combat.

5. Some consider the chevrotain a living fossil.

Chevrotain sticking its tongue out
Josh More, Flickr // CC BY-NC-ND 2.0

Chevrotains are the most primitive of ruminants. Like deer and similar hoofed animals, they have even-toed hooves and a multi-chambered stomach. But unlike deer, chevrotains have a three-chambered stomach instead of four, and they lack horns or antlers. They haven't changed or evolved much during their time on Earth. Scientists see them as an evolutionary link between ruminants and non-ruminants.

6. Taking a dip is the water chevrotain's best defense.

The water chevrotain is known for its ability to dive underwater when it senses a predator nearby. The miniature swimmers scrunch up and walk on the bottom of rivers and streams to prevent being picked up by the current. If there are any reeds or plants around, the animals will grab them to stay tethered. Chevrotains are able to hold their breath for about four minutes.

While hiding from hungry predators, the water chevrotain can reemerge to get some air before diving back down. Still, the animal tires easily, and can only swim for short periods of time.

7. Childbirth is an expedited experience for chevrotains.

Chevrotain in a woodland
aee_werawan/iStock via Getty Images

After getting pregnant, a female chevrotain will carry the offspring for five to nine months, depending on the species. The baby can usually stand on its own within one hour of being born. Mothers will visit their young periodically for feedings and stand on three legs while nursing.

Chevrotains are known for their ability to be almost continuously pregnant—greater and lesser Malay mouse deer can mate again only a few hours after giving birth.

8. Chevrotains are shy wallflowers.

Chevrotain in a woodland
cowboy5437/iStock via Getty Images

Due to their small size, chevrotains are preyed upon by many different animals. Lacking antlers or horns for protection, the tiny animals are forced to lead secluded lives. Some species are nocturnal and very rarely seen. Chevrotains are very shy and often graze alone, only coming together to mate. They communicate with a series of smells and noises; this timid behavior makes it difficult for scientists to study them.

9. Chevrotain hooves make a lot of noise.

Chevrotain in a woodland
asxsoonxas/iStock via Getty Images

Although normally peaceful, a male will angrily beat his hooves when agitated—they can stomp around four to seven times a second. This “drum roll” technique wards off predators and warns other chevrotains in the area that there’s danger.

Additional sources: "Water Chevrotain," Amazing Animals of the World; "Chevrotains (Tragulidae)," Grzimek's Animal Life Encyclopedia; Mammals IV, Gale Virtual Reference Library

'Lost Species' of Tiny, Rabbit-Sized Deer Photographed in Vietnam for the First Time in 30 Years

Global Wildlife Conservation
Global Wildlife Conservation

The silver-backed chevrotain, also called the Vietnamese mouse-deer, is elusive. It's so elusive that scientists had feared it was extinct after none had been photographed for decades. But as The Washington Post reports, the first images taken of the mammal in nearly 30 years prove that the species is still alive in the woods of Vietnam.

No larger than small dogs, chevrotains are the tiniest ungulates, or hoofed animals, on Earth. They have vampire-like fangs and skinny legs that support their bodies. Silver-backed chevrotains are characterized by the silver sheen of their tawny coat.

The tiny population native to Vietnam has been devastated by poachers in recent decades. That, and the animal's natural shyness, make it incredibly difficult to study. Before this most recent sighting, the last time scientists had recorded one was in 1990.

Global Wildlife Conservation, the Southern Institute of Ecology, and the Leibniz Institute for Zoo and Wildlife Research teamed up in hopes of documenting the lost species. Researchers interviewed residents and government forest rangers in the Vietnamese city of Nha Trang about the silver-backed chevrotain, looking for tips on where to find one. Residents said that while populations had been hit hard by hunting, the animals were still around.

Based on this local ecological knowledge, scientists set up three camera traps in the Vietnamese woods. In just five months, they captured 275 photographs of the little mouse-deer. They then installed 29 additional cameras and snapped 1881 new images in that same length of time.

“For so long this species has seemingly only existed as part of our imagination," Global Wildlife Conservation associate conservation scientist An Nguyen said in a statement. "Discovering that it is, indeed, still out there, is the first step in ensuring we don’t lose it again, and we’re moving quickly now to figure out how best to protect it.”

Now that a silver-backed chevrotain population has been located, researchers plan to conduct the first-ever comprehensive survey of the species. Once the data is collected, it will be used to build a plan for the species' survival.

[h/t The Washington Post]

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