There’s a huge diversity in the animal kingdom, and sometimes the little guys get overlooked.
The smallest fish is found in the acidic peat swamps and blackwater streams of Indonesia. Paedocypris progenetica females grow up to 10.3 millimetres (0.41 in), with males reaching 9.8 millimetres (0.39 inches). These miniscule members of the carp family are translucent, and their brains are not protected by a skull.
Weighing half as much as a British penny at just 1.8 grams (0.063 ounces), and growing to five centimeters (2 inches) long, the smallest living bird is the bee hummingbird. Also called the Helena hummingbird, this tiny bird is found on the island of Cuba. It drinks eight times its mass every day and is often, unsurprisingly, mistaken for a bee.
The smallest known species of snake is the Barbados threadsnake. Living only on the Caribbean island, it averages 10 centimetres (3.9 inches) in length and is thought to live on a diet of ants and termites. Threadsnakes are burrowing animals, and a female Barbados threadsnake produces just one egg at a time.
Frog (and vertebrate!)
Found in Papua New Guinea, Paedophryne amauensis frogs are both the smallest frogs and the smallest of all the animals with backbones. They average just 7.7 millimetres (0.3 inches) in length and live among the leaf litter of tropical forests.
The award for smallest insect goes to the microscopic parasitic wasp Dicopomorpha echmepterygis, a type of firefly. Adult males can be as small as 139 μm (0.1mm, 0.005 inches) in length, which makes them smaller than some single-celled organisms.
These tiny wasps parasitise the eggs of barklice. Males are blind and wingless (apterous), mating with their sisters and die without ever leaving the host egg. Females have thin wings and can leave the louse egg to find a new host.
The speckled padloper tortoise measures up to 11 centimetres (4.3 inches) in length and reaches a weight of 95-165 grams (3.4-5.8 ounces). Found only in western South Africa, this tiny tortoise earns its name from the hundreds of black spots covering its shell. Most tortoises have four toes on each foot, but this species has five on the front pair.
Two members of the genus Sphaerodactylus, the dwarf gecko and the Virgin Islands dwarf sphaero, share the titles of smallest lizard and smallest reptile. Both species are found in the America and have an average snout-vent length (body not including tail) of 16 millimetres (0.6 inches).
Cuvier’s dwarf caiman, found in parts of South America, is the smallest crocodile at just 1.6 metres (5.2 feet) long. These crocodilians, weighing around six kilograms (13 pounds), shelter in burrows and have bony scales to protect them from predators.
There’s some competition for the smallest mammal crown. The Kitti’s hog-nosed bat (or bumblebee bat) is three to four centimetres (1.2-1.6 inches) long, weighs 1.5-2 grams (0.053–0.071 ounces), but the Etruscan shrew weighs in at an average of 1.8 grams (0.063 ounces). The vulnerable bat, found in Thailand and Myanmar, has the smallest skull of any mammal and a characteristic upturned snout. The shrew, now living on most continents, has the largest brain relative to body size of any animal, and hunts prey the same size as itself.
Madame Berthe’s mouse lemur is the smallest member of the primates. Native to western Madagascar, it grows to an average of nine centimetres (3.5 inches) long. Only describes in 2000, these little lemurs live alone and forage for fruit and gum from trees.
The least weasel is the smallest of the meat-eating mammals. It is 11-26 centimetres (4.5-10.2 inches) long, and males weigh around 57 grams (2 ounces). Despite their small size, least weasels are fierce hunters and can take down prey larger than themselves.
The world’s smallest deer is the northern pudú, just 36 centimetres (14 inches) tall at its shoulder. It weighs around 4.5 kilograms (10 pounds) – the same as a large pet cat. These solitary, stocky deer live in the Andes mountains where they climb and jump to avoid being eaten.