Fish are the most prominent predators of leeches, and other predators include aquatic birds, water bugs, crayfish, turtles, snakes and other leeches. Regardless of their habitat, all leeches are preyed upon. However, the predators do vary according to location.
Fish are the most populous animals in areas where leeches live, and their feeding habits keep leech populations down. If a body of water has an unusually large number of leeches, it is a sign that there is a relatively small fish population. Red-eared sunfish hunt leeches voraciously, but nearly all kinds of freshwater fish eat leeches.
Leeches are an important protein source for many aquatic birds, although they usually only account for a small percentage of their complete diets. If a bird preys on fish and insects, it usually also preys on leeches. Leeches are a major food source for ducks.
Many aquatic, omnivorous turtles feed on leeches, especially snapping turtles, mud turtles, sliders, painted turtles and musk turtles. Like birds, turtles incorporate leeches into their diet, but they feed on many other creatures as well.
Saltwater and land leeches are preyed upon by virtually any omnivorous animal. Land leeches are commonly eaten by monkeys, lizards and robins, and saltwater leeches are often preyed upon by puffer fish, grouper and eels.