Earth hosts a vast range of mammals that come in all shapes and sizes. At one end of the size spectrum is the blue whale, whose massive body makes it the largest living mammal and the largest animal that has ever lived on the planet.
Still, not all mammals are giants. At the other end of the scale sits the Kitti’s Hog Nosed bat, which holds the world record for being the smallest mammal, possessing a body mass of less than an ounce. These tiny mammals may look helpless, but their small size can offer a number of advantages.
Smallest Mammal: Kitti’s Hog-Nosed Bat/Bumblebee Bat
Average Size: 29-33 mm
Average Weight: 1.7g - 2g
The Kitti’s Hog-Nosed Bat is the smallest-sized mammal in the world, with a body length of just 29-33 mm. It is named after Kitti Thonglongya, the Thai zoologist who first discovered the bat in 1974. This bat possesses the smallest mammalian skull and is smaller than the largest species of bumblebee, hence its nickname, the Bumblebee Bat.
And this tiny bat resides in colonies of less than 100 bats in the caves of Thailand and Myanmar.
Lightest Mammal: Etruscan Shrew
Average Size: 36-52 mm
Average Weight: 2.1g
Though the average weight of the Etruscan Shrew slightly tops that of the Bumblebee Bat, the former is still classed as the lightest mammal in the world. This is because some Etruscan Shrews can weigh just 1.5g as fully grown adults, the lowest recorded weight for a mammal.
Despite its small size, this miniature shrew has a mammoth appetite and often eats twice its body weight daily. Additionally, it has an extremely fast heart rate of 1,500 bpm (compared to humans who have an average rate of 72 bpm).
The only competition for the Etruscan Shrew’s light weight is the now-extinct Batodonoides vanhouteni, which may once have roamed North America. Experts think this miniature shrew-like species may have weighed as little as 1.3g.
Smallest Mole: American Shrew Mole
Average Size: 69-84 mm
Average Weight: 10g
The American Shrew Mole is the smallest mole species, with a body of only 69-84 mm long. Located in the northwest of the US and the southwest of British Columbia, these tiny creatures make their homes in moist forest environments.
Like its relatives, the American Shrew Mole possesses a lengthy snout and pointy claws that help it burrow. Still, a critical difference between it and other moles is that the American Shrew mole spends most of its time foraging for food above ground.
Smallest Armadillo: Pink Fairy Armadillo
Average Size: 105 mm
Average Weight: 120g
The Pink Fairy Armadillo lives up to its magical name with its unique appearance. Also known as pichiciegos, these tiny armadillos are nocturnal and adapted to desert life, residing in the grasslands of central Argentina. These small armadillos have a carapace (shell) similar to their larger relatives - however, it is thinner, softer, and more flexible than other armadillos.
These elusive creatures are rarely seen; a nocturnal nature means they spend much of their time underground. In addition, they cannot survive outside their natural habitat, making them a tricky species to study.
Fairy Armadillos are pink because they have a network of blood vessels running beneath the carapace that show through this thin covering. Though it is much softer than the average armadillo, it still offers sufficient protection while allowing the little creature to roll into a tight ball if threatened.
Smallest Marsupial: Long-Tailed Planigale
Average Size: 60 mm
Average Weight: 4.3g
With a body length of only 55-65 mm, the Long-Tailed Planigale is the smallest marsupial in the world. These nocturnal creatures possess strong hunting skills and can hunt insects that are just as large as themselves. Sometimes these brave predators will also hunt small mammals.
Their tiny size and flattened head allow the Planigale to squeeze into crevices and escape the grasp of deadly predators; it also helps them source food in places other prey cannot access. Meanwhile, their (marsupial) pouch faces backward to keep it clean as they burrow into the ground.
Smallest Possum: Pygmy Possum
Average Size: 70 mm
Average Weight: 8.4 g
The world’s smallest possum is the Pygmy Possum, with an average body length of 70 mm. They may look like mini chinchillas, but they belong to the marsupial family (which includes kangaroos, koalas, and wombats). Their prehensile tail can stretch between 75-105 mm and is used for hanging upside down in trees.
Located in Australia, Indonesia, and Papua New Guinea, the Pygmy Possum is nocturnal and hibernates during winter. When it gets cold, the possum will roll into a ball, use its ears to cover its eyes, and enter a state of torpor. While hibernating, the Pygmy Possum receives all the nourishment it needs from fat reserves in its tail.
But limited habitats mean the IUCN lists these tiny creatures as critically endangered. Not only do road developments, ski resorts, and bushfires lead to habitat destruction, but they can also be subject to pesticides from the Bogong moths that make up a significant part of their diet.
Smallest Rodent: Pygmy Jerboa
Average Size: 44 mm
Average Weight: 3.8g
The Pygmy Jerboa and the African Pygmy Mouse share the title of the world’s smallest rodent. Still, on average, the Pygmy - or Dwarf - Jerboa tends to be smaller (average weight of 3.8g, compared to 7.2g). Native to Afghanistan and Pakistan, these creatures can survive harsh desert environments by burrowing beneath small bushes.
In 2010, this cute little creature went viral for looking like a cross between a mouse and a kangaroo. Their legs help them jump at impressive lengths, allowing them to move quickly over the vast desert environments they call home.
Smallest Primate: Madame Berthe’s Mouse Lemur
Average Size: 120 mm
Average Weight: 33g
The Mouse Lemur is the world’s smallest primate and a species that is unique to Madagascar. These nocturnal creatures forage insects, fruits, and flowers through the night. These small omnivores are no bigger than a softball and mainly feed on honeydew, a sweet byproduct created through insect digestion.
Despite foraging and eating alone, the mouse lemur does enjoy companionship and spends more than 50% of its time sleeping alongside other mouse lemurs.
Smallest Carnivore: Least Weasel
Average Size: 180 mm
Average Weight: 375g
The Least Weasel (also known as a weasel or common weasel) may be one of the largest creatures on the list, growing to lengths of 18 cm. Still, it is a worthy contribution to the list for holding the title of the smallest carnivore in the world. They aren't the only creatures on this list that eat other animals (such as insects), but they are the only “true” carnivore, meaning they need meat to survive.
This tiny creature may look harmless, but it is a cunning hunter that can terrify any small rodent it encounters.