Anna's Animal Facts: Leeches



Did You Know:  There are 70-1,000 different species of leeches in the world.

Did You Know:  Every continent on the planet has leeches, except Antarctica.

Did You Know:  As leeches fill themselves up their bodies grow and swell to many times their original size and they can survive losing up to 9/10 of their bodyweight.

If you’re a backcountry enthusiast, or even just a person who enjoys nature, you have probably encountered leeches.  Most people find leeches attached to their skin after a swim in the lake and regard them as a nuisance, but leeches are actually pretty cool creatures.  For starters, most leeches appear black or brown, but if you look closely, some leeches have intricate markings on their bodies. The common North American leech has a greenish-grey body with orange stripes on its sides and orange dots on its back, and there are other leeches you may see that have reddish markings on their bodies.

One of the most well-known facts about leeches is that they suck blood, but not all leeches are bloodthirsty vampires looking to suck the very life out of human beings.  Although the majority of leeches are hematophagous, meaning that they feed on blood, there are very few leeches that are interested in human blood. There are even a few species of leeches that eat dead plant material and small insects.


Different species of leeches vary in size and most commonly are 0.3 to 3 inches in length, however a species of leech called the giant Amazon leech lives for 20 years and grows up to 18 inches long. That’s a leech that grows to over a foot long!  Luckily, the giant Amazon leech does not live in North America.  Different species of leeches have different lifespans, with some living for upwards of ten years.

Although you might not like leeches, catfish, dragonfly larvae, and largemouth bass all love them.  Walleye or Pickerel also like to eat leeches, so many fishermen will use leeches as bait.

Anyone who has been bitten by a leech will know that the bite is painless and the leech can often go unnoticed.  When a leech pierces its prey’s skin it produces an anesthetic that reduces the pain and makes it easier for them to suck the blood.

If you have ever found a leech stuck to you, you probably noticed they are hard to get off, but there is no need to panic.  Over the many years that my family has been camping we have found that the best way to get a leech off of you is to take it Auntie Lisa.  She is a leech whisperer and coaxes them to let go by gently pressing their heads to the side and breaking the suction with her fingernail (we used to pour salt on them, but then we read that this can make them regurgitate (i.e. throw-up) into the wound and besides being dangerous, that's just plain gross).   Once the leech is safely removed you can throw it back in the lake, stream, pond, or whatever body of water you happened to pick up the leech from.

You can find a diagram of how to remove a leech here.