Averaging 9.25-11.6 inches (23.5-29.5 centimeters) in length, the endangered pygmy rabbit, or Brachylagus idahoensis, lives primarily on the West Coast of the United States. They tend to live in tall, dense sagebrush, which also makes up the majority of their diets. The smallest species of shark on Earth is the dwarf lanternshark or Etmopterus perryi, which grows to about 8.3 inches (21.1 centimeters). Their bodies contain light-emitting organs that allow them to camouflage in sunlight and attract small animals in darker, deeper waters.The pygmy marmoset, or Cebuella pygmaea, is the world's smallest monkey. The tiny creatures live in the rainforests of South America and tend to be between 4.6-6.2 inches (11.7-15.7 centimeters) tall, without counting their tails.Believed to be the world's smallest snake, the Barbados threadsnake, or Leptotyphlops carlae, grows to only about 4.1 inches (10.4 centimeters) on average. Some scientists believe that the entire population of threadsnakes exists within a few square kilometers in Barbados.The nocturnal mouse lemur, or Microcebus berthae, is another tiny primate species, Found only on the island of Madagascar, they live and hunt alone and grow to be a mere 3.6 inches (9.1 centimeters). Known by many as the Turquoise or Electric Blue Gecko, the average adult Williams' dwarf gecko, or Lygodactylus williamsi, is just 3 inches (7.6 centimeters) long. Found only in Tanzania, the species is considered critically endangered.The world's smallest bird, the bee hummingbird, or Mellisuga helenae, usually grows to be about 2.2 inches (5.6 centimeters) long. Endemic to Cuba, the bird weighs less than a dime and can beat its wings up to 200 times per second.The smallest species of tortoise on Earth is the speckled padloper tortoise, or Homopus signatus. It grows to be between 2.4-3.1 inches (6.1-7.9 centimeters) long. The entire population of the species exists exclusively in the Little Namaqualand region of South Africa.A typical Baluchistan pygmy jerboa, or Salpingotulus michaelis, has a body length of 1.7 inches (4.3 centimeters), making it the smallest rodent in the world. Native to Pakistan and Afghanistan, the creature has relatively long legs that sometimes inspire comparisons to kangaroos.Without factoring in its tail length, the adult Etruscan shrew, or Suncus etruscus, averages about 1.5 inches (11.4 centimeters) long. Found in a belt of land that extends from the Mediterranean region to Southeast Asia, these tiny animals eat up to 25 times per day because of their high metabolism. Averaging between 1.1-1.3 inches (2.8-3.3 centimeters) with head and body combined, the Kitti's hog-nosed bat, or Craseonycteris thonglongyai, is the world's smallest mammal. Found in Thailand and Burma, the endangered species lives primarily in limestone caves.The average adult Brookesia micra chameleon grows to be just over 1 inch (2.5 centimeters) long. That's small enough to sit on top of a human finger. Researchers discovered the species, which is endemic to Madagascar, in early 2012. The Virgin Islands dwarf sphaero, or Sphaerodactylus ariasae, lives in the Caribbean and tends to be just 0.6 inches (1.5 centimeters) long. Thought to be the world's smallest reptile, researches believe the species exists only in the Dominican Republic's Jaragua National Park.The Monte Iberia eleuth, or Eleutherodactylus Iberia, is the smallest frog in the Northern hemisphere. It's tied for the world's smallest tetrapod with another frog, Brachycephalus didactylus. Both reach only about 0.4 inches (1 centimeter) in size.