Leeches are segmented worms primarily found in aquatic environments. Distant relatives of earthworms, they share a segmented body structure. While their presence can cause apprehension, understanding their nature helps demystify these organisms.
Leeches Found in Michigan
Leeches are found throughout Michigan’s diverse aquatic ecosystems, including its lakes, ponds, rivers, and wetlands. Michigan is home to at least 19 different species, with some estimates suggesting over 40 are present. Most of these species do not feed on human blood.
Many Michigan leeches are predatory, feeding on small invertebrates like worms, snails, and insect larvae, or scavenging decaying organic matter. A small percentage attach to warm-blooded animals, including humans, if given the opportunity. Even when they do, human encounters are uncommon, and leeches are not considered dangerous.
Spotting Leeches and Their Homes
Leeches appear as flattened, worm-like animals, varying in color from black, brown, or green, to speckled or striped patterns. They have a sucker at each end of their body, used for attachment and “inch-worm” like locomotion. Sizes range from less than an inch to several inches when extended, but most encountered freshwater leeches are relatively small.
They prefer shallow, calm, warm freshwater environments, found among abundant aquatic vegetation, muddy bottoms, or decaying leaves and other organic debris. They cling to the underside of stones, logs, or submerged plants. Leeches are most active during warmer months and may be attracted to water disturbances.
Staying Safe Around Leeches
Encounters with leeches in Michigan’s waters are harmless, as they do not transmit diseases to humans. If a leech attaches, it will detach on its own after feeding, usually within 20 minutes. To remove one, gently slide a fingernail or a thin, flat object like a credit card underneath the leech’s oral (thinner) end to break its suction. Flick it away before it reattaches.
Do not pull a leech, as this can leave mouthparts in the skin, causing irritation or minor infection. Avoid using substances like salt, heat, or alcohol to detach a leech, as this can cause it to regurgitate stomach contents into the wound, increasing infection risk. After removal, clean the area with rubbing alcohol or an antiseptic and apply a bandage for any minor bleeding, which is normal due to the anticoagulant leeches release.
To avoid leeches, swim in deeper waters away from heavily vegetated or mucky areas. Wearing protective clothing, such as long pants or water shoes, can provide a physical barrier. Check your skin, especially after wading in shallow, stagnant water, for prompt detection.