What Do Leeches Eat? Comparing the Feeding Habits of Blood-Feeding and Snail-Eating Species

The leech, commonly known as the bloodsucker, is an annelid often found in freshwater environments such as rice paddies, ponds, ditches and swamps. Its feeding habits vary markedly from species to species and can be broadly divided into two major groups: blood-feeding and non-blood-feeding.

Blood-feeding leeches take animal blood as their main food and have a fairly broad host range, including aquatic animals such as fish, frogs and turtles, and they will also bite livestock such as cattle and sheep that pass by the water's edge; a few species will even attach to human skin. They cling firmly to the host's body surface with their front and rear suckers, and when feeding they secrete anticoagulant substances that keep the wound bleeding, and after one full meal they can go a long time without feeding again.

Non-blood-feeding leeches mainly prey on small animals, among which common species such as the wide-body golden-line leech (Whitmania pigra) feed primarily on snails, for example field snails, river snails and the young of freshwater mussels, and they also prey on earthworms, aquatic insect larvae and small animals in humus. These leeches have a relatively large appetite and likewise use their suckers to hold their prey in place when hunting.

Under artificial farming conditions, people usually feed leeches with feed such as river snails, earthworms or coagulated animal blood, and when feeding they need to keep the water clean to avoid leftover feed rotting and affecting the environment. In addition, leeches are used as animal medicinal materials in traditional medicine, which is also why many people take an interest in their feeding habits and farming methods.

If you are bitten by a leech in the wild, there is no need to panic too much, and you must by no means pull it off by force; you can use salt grains or gentle tapping to make it drop off on its own, then rinse the wound with clean water and apply appropriate pressure to stop the bleeding.