The presence of the parasite in the skin interrupts normal growth patterns and can cause extra limbs to form, or no limbs at all, and the same happens around the eyes. These deformed amphibians are much less efficient at avoiding predators, hence they are probably more likely to become a garter snake lunch. Once inside the garter snake, the parasite attaches itself to the snake's gut and completes its life cycle. This phenomenon has been documented in Californian frogs and salamanders. The parasite has not been found in the frogs of the Great Lakes basin, but is likely to be present due to the common presence of the garter snake.
Deformities can also result from physical injury.
People who keep tadpoles in captivity have observed that tadpoles will bite each other if they are kept in dense quarters. They can scrape skin off each other and even bite off legs. This is particularly true for the bullfrog which can be a robust three or four inches in length. Generally, scientists suspect there are multiple causes of deformities and that more than one stress may be acting at any individual pond. There seems to be a natural rate of deformity of about one per cent of frogs in normal, healthy populations.