A tadpole can be identified by the length of the body, the length and shape of the dorsal tail fin and the ventral tail fin, the tail musculature, and the placement of the eyes and nostrils. The tadpole's habitat and the time of year it's found are also clues. Still, identifying tadpoles remains difficult because tadpoles are small and are in a constant state of metamorphosis.
One common tadpole is that of the American toad. This tadpole is dark in color and about 3/4 inch to 1 inch long. The tail fin is colorless and has a round tip. The nostrils are small, and the eyes are small and found on the top of the tadpole's head. This tadpole can be found in lakes and the shallow ends of ponds from May to August. They're gregarious and can be seen in groups of hundreds or even thousands.
The leopard frog tadpole is seen at the same time as the American toad tadpole, though it can also be seen in the early fall. Sometimes, the tadpole will overwinter. The dorsal tail fin has a slight arch, and the tail and body are pigmented. It's found among the vegetation in ponds, marshes and drainage ditches.