The Nile Monitor Lizard (Varanus niloticus) is one of the largest species on earth, and it can reach 7 feet in length. These lizards feed on rodents (rats, mice and so forth,) and in captivity they can be fed well cooked meat, boiled eggs and reptile diets. Nile Monitor lizards occur in different shades of brown, and they feature large dark spots and a few lighter and smaller ones.