Last month, the BBC released a clip from its new 'Wonders of the Monsoon' series that depicts something never before captured on film: a giant red leech gulping down a worm ... whole.

Now, because leeches are very rarely in the spotlight, I thought it would be fun to take a dive into the muck and find out what other tricks leeches have up their sleeves. Not that leeches have sleeves, mind you. Leeches essentially are sleeves.

Anyway, without further ado, a list of all the reasons you should give these bloodsuckers a little respect.

leech eating habits grimly DIVERSE 

There are around 700 species of leeches known to science, ranging from the tiny to the terrifying. The largest stretches past 18 inches in length.

While leeches are known almost exclusively for their ability to latch onto larger animals and suck their blood, leech behaviour varies widely depending on the species. Some leeches parasitise insects, snails or other invertebrates, inserting a proboscis or tube and sucking the creature dry, not unlike a spider. Others eat their victims whole, like you saw in the video above.

As for the leeches you’re more familiar with, these come in both the two- and three-jaw varieties. The two-jaws gnaw into their victims' flesh and leave a V-shaped bite-mark behind, probably saying, “Very nice to have made your acquaintance!” The three-jaws, on the other hand, have a little more disposable income and are always going on about it to anyone who will listen. They leave a Mercedes symbol as their calling card.

leeches Can get you on land

You may think you’d be safe from leeches so long as you stay out of all Fire Swamps and Bogs of Eternal Stench. But dear reader, it is not so.

Leeches can thrive in many different habitats, from saltwater to freshwater streams. And where the leaf litter is moist enough, some species of leeches prowl the land.

These enterprising annelids can either snag an unlucky host as it happens by or actively pursue prey by inchworm-ing their way toward anything that trips off the sensors in their skin. According to The Book of Deadly Animals by Gordon Grice, it’s said that some tropical leeches are even "aggressive enough to burrow through one’s socks".

Leeches make good mommies

You may not expect a glorified sucker worm to do much in the way of parenting, but some species of leeches can be downright doting.

In Dr. Tatiana’s Sex Advice to All Creation by Olivia Judson – a seriously illuminating read, if you’re ever looking to curl up with several hundred pages about animal coitus – we learn that leeches routinely hover over their egg cocoons and protect them from predators. Once they’re born, baby leeches of the species Helobdella striata glue themselves to mom’s belly and tag along while she’s out running errands. If they’re good, she’ll even hunt down some tiny worms and feed the brood.

Another species, Marsupiobdella africana, carries the next generation of wiggle worms around in a specialised pouch like a cute little koala.

They also make great meteorologists!

In 1850, an inventor and museum curator named Dr George Merryweather noticed that changes in barometric pressure caused freshwater leeches to become agitated. Naturally, this made him want to take twelve of the animals and attach them each to a chain, lock them in individual glass tubes, and rig each with a bell. 

Merryweather called his contraption the 'Tempest Prognosticator' or 'Atmospheric Electromagnetic Telegraph conducted by Animal Instinct', though it’s remembered simply as the 'leech barometer'. 

Tests over a year’s time proved the leeches to be rather accurate predicting incoming thunderstorms. The more bells ringing, the stronger the storm. 

I don’t know about you, but I think I’d watch a lot more local news if they replaced all the weather people with jars full of leeches.

Leeches can stop an army

Napoleon army leeches_2014_10_28
Original image before modifications: Andrew Becraft, Flickr (Creative Commons)

Many a soldier has gone traipsing through the muck only to emerge with a few hitchhikers. Luckily, in most cases a leech can be dislodged using nothing more than your thumbnail. That is, when you can find them.

In 1799, the men in Napoleon’s army started coming down with a host of fearful symptoms. They coughed up bloody mucous, vomited frequently, and had a “painful stinging in the posterior”. Other symptoms included throat swelling, frequent haemorrhages, trouble swallowing, shortness of breath, loss of sleep, emaciation, and eventually death. The army’s chief surgeon didn’t know what to make of the afflictions until he started noticing weird, darkly coloured growths in the men’s noses and throats. Growths that moved when you poked them.

You see, some leeches start off life so small, they can easily hide in sip of river water. No one notices until they start to grow inside the human body, where they can lead to suffocation, blood loss and death.

Glad you don’t live in Napoleon’s time? A Scottish woman recently discovered a three-inch leech living in her nose because it would come peeking out when she got in the shower. Doctors said the woman was lucky, as the leech might eventually have wormed its way into her brain, but I’m not sure anyone with a parasite peeping out of a nostril should consider themselves all that fortunate.


Dr. Tatiana’s Sex Advice to All Creation, Olivia Judson

Leech, Robert G. W. Kirk, Neil Pemberton

The Book of Animal Ignorance, John Lloyd, John Mitchinson

The Book of Deadly Animals, Gordon Grice

H/t to Robbie Gonzalez at io9 for the giant red leech video. 

Top header image: Pat Joyce, Flickr