The American alligator, also known as the Mississippi River crocodile or the Mississippi River crocodile, is a large species of crocodile in the Western Hemisphere and the ninth largest member of the crocodile family. Male crocodiles can reach a body length of over 4 meters, while females are less than 3 meters. Juvenile crocodiles are black in color, with irregular yellow horizontal stripes on their bodies. As adults, these yellow stripes will gradually be obscured by melanin and algae. The mouth and nose of American alligators are round and wide, with 17-22 teeth on each side of the upper jaw and the same number of teeth on the lower jaw. There are a total of 18 horizontal rows of keratinized scales on the back of the body, of which 8 rows are larger; There are incomplete fins between the toes. The American alligator is mainly distributed in the southeastern United States and inhabits freshwater wetlands.

Nile crocodile is a large crocodile belonging to the family Crocodylidae in the order Crocodiles. Nile crocodiles have a large body size, ranging from olive green to coffee colored, with black spots and a mesh pattern; The fourth tooth of the lower jaw protrudes outward from the depression of the upper jaw; There are 5 anterior teeth, 13-14 maxillary teeth, and 14-5 mandibular teeth, for a total of 64-68 teeth; The tail is strong and powerful. The adult Nile crocodile weighs up to one ton. The juvenile Nile crocodile is dark yellow brown in color, with obvious horizontal stripes on its body and tail. As an adult, the color of the horizontal stripes becomes lighter.