11 of the Smallest Mammals in the World

extremely tiny monkey, a pygmy marmoset, clasping the middle finger and thumb of human hand

bluedogroom / Shutterstock

Though small size may seem like a meager trait, in the biological world, it can come with some significant advantages.

Small mammals can occupy ecological niches that are inaccessible to larger animals, and their petite frames make it easier to hide undetected, burrow into minor crevices, or climb upon the flimsiest of branches.

They're also incredibly cute. Here's our list of some of the world's smallest mammals.

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Etruscan Shrew

very tiny grey shrew with ears that protrude and pointy nose resting between knuckles on human thumb

Trebol-a / Wikimedia Commons / CC BY-SA 3.0

There are many tiny shrews, but this pipsqueak takes the cake as the smallest. The Etruscan shrew is the smallest mammal in the world by mass. On average, it weighs less than .14 ounces and has a body length of about 1.57 inches.

For such a tiny animal, however, it has a huge appetite — it typically eats about twice its own body weight every day.

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Pygmy Jerboa

tiny mouse like creature with long legs and long tail

reptiles4all / Shutterstock

Pygmy jerboas make up the rodent subfamily Cardiocraniinae and are the smallest rodents in the world. Their bodies start at 1.6 inches long and they have tails up to 3 inches long.

For their size, these minuscule mammals sure can jump. Jerboas have kangaroo-like legs that allow them to leap distances far exceeding their body lengths, an adaptation that helps them move quickly over the vast, arid deserts in Northern Africa and Asia that they call home.

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Bumblebee Bat

closeup of hand holding tiny bumblebee bat

Merlin Tuttle's Bat Conservation

The bumblebee bat, also known as Kitti's hog-nosed bat, is the world's smallest bat and the smallest mammal in the world based on skull size. Weighing around .07 ounces (less than a penny) and with a length of 1.14 inches, it's so small that you might confuse one for a bumblebee if it went buzzing by your ear in the night.

Unfortunately, its delicate size is also indicative of its biological status. The IUCN lists the animal as near threatened, and a few roosting populations are at risk of extinction due primarily to human activity.

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Mouse Lemurs

tiny lemur with golden brown fur on face and grey, white and brown fur on body hanging on to the very end of a thin branch with closed white blossoms

Ryan M. Bolton / Shutterstock

These adorable creatures are the world's smallest primates, measuring up to 11 inches in length including their tails. The smallest species is the Madame Berthe's mouse lemur, which measures just about 3.62 inches in length and weighs only about an ounce.

These softball-sized omnivores eat alone and mostly dine on "honeydew," a sugary byproduct of insect digestion. However, despite spending their foraging time alone, they do sleep with other mouse lemurs about half the time.

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Least Weasel

tiny brown and white weasel with long fluffy squirrel like tail on a weathered curved piece of wood

Bering Land Bridge National Preserve / Flickr / CC by 2.0

This finicky, wise little weasel is the smallest species of the Carnivora order, making it the tiniest true carnivore in the world. North American least weasel males only reach 7 inches, and the females grow to 5 inches. It weighs less than 1.5 ounces.

It might be hard to imagine something so small being such a cunning hunter, but the lesser weasel is the worst nightmare of any small rodent it encounters. They exhibit a much bigger, more ferocious personality than their small size might suggest.

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Pygmy Possum

mouse like animal about the size of a finger with large ears and diminutive pointy snout

Janelle Lugge / Shutterstock

Ranging in length between 2 and 4 inches and often weighing barely over .35 ounces, these mini marsupials are found hanging upside down in trees in Australia and New Guinea.

IUCN lists one species, the Mountain Pygmy Possum, as critically endangered. This species has a limited habitat in the alpine areas of Australia. Ski resorts, road construction, and extensive bushfires have led to habitat destruction. The migratory Bogong moth makes up a significant portion of their diet and carries arsenic from pesticides in breeding grounds to the mountain. Scientists believe this is one factor leading to the decreasing population.

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African Pygmy Mouse

tiny brown and white African pygmy mouse eating seeds

AleXXw / Wikimedia Commons / Public Domain

Mice are known for their small size, but the African pygmy mouse takes that trait to the extreme. Measuring 1.2 to 3.1 inches in length and weighing as little as .11 ounces, it is the world's smallest mouse. It is so petite that it typically stays hydrated by licking dew off tiny pebbles that it cleverly stacks in front of its burrow.

Some people keep these elfin mice as entertaining pets. Owners must remain hands-off with them, though, as they are incredibly fragile.

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Pygmy Marmoset

diminutive monkey in profile with long golden brown tail with rings, brown and black and grey hair on body standing on a tree branch that is much bigger than it is pygmy marmoset

Cuson / Shutterstock

Occasionally referred to as the "pocket monkey" because they can easily fit into your breast pocket, these adorable, curious animals native to the Amazon rainforest are the world's smallest monkeys. It's hard to imagine a monkey getting any smaller; pygmy marmosets rarely exhibit a length greater than about 5.35 inches and typically weigh 4.2 ounces.

Their diet is as unique as their size. They use their sharp teeth and nails to gouge holes in trees and eat the sap, gums, and resins found inside and also consume insects.

Evolutionary biologists from the University of Salford released a study in February 2018 announcing the pygmy marmoset is actually two different species: one that lives in the north Amazon River area and the other in the south.

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Long-Tailed Planigale

grey brown animal that looks like a rodent on red sand

Alan Couch / Flickr / CC by 2.0

Native to Australia, long-tailed planigales are the world's smallest marsupials. They weigh less than .15 ounces and reach lengths averaging 2.32 inches, including the tail.

Their small size and flattened heads allow planigales to squeeze into crevices and cracks any other mammal would find impossible. This ability enables them to find food and to hide from predators. Their pouches face toward the rear to keep it clean as they navigate these crevices.

These fierce nocturnal carnivores hunt insects and even young mammals almost as large as the planigale.

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American Shrew Mole

two dark grey tiny animals with long pointy noses on forest floor dwarfed by tendrils of moss

Owen Borseth / Wikimedia Commons / CC BY-SA 4.0

The smallest species of mole in the world is the American shrew mole. This tiny mammal measures 4.72 inches long, including the tail, and weighs about .35 ounces. The American shrew mole doesn't even have external ears and has minuscule eyes that are almost invisible.

Found in the U.S. Northwest and Canada's British Columbia, these adorable underground dwellers have smaller front paws than most other moles, a trait that is similar to a shrew. These moles travel in groups of 11 or more and spend more time above ground than other moles.

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Pen-Tailed Tree Shrew

small brown and grey tree shrew sitting on a tree branch

Paul J. Morris / Flickr / CC BY-SA 2.0

The smallest tree shrew in the world is the pen-tailed tree shrew, which can weigh as little as 1.41 ounces and measure barely more than 5 inches. Not to be confused with the true shrews or elephant shrews, tree shrews are a group of mammals set apart.

Tree shrews appear closely related to primates, so much so that there is debate as to whether to class them as primates or insectivores. Instead, they belong to their own order: Scandentia. The pen-tailed tree shrew is the sole member of its genus.

Sometimes known as a party animal, the primary diet of the nocturnal pen-tailed tree shrew is fermented alcohol from the bertam palm. It consumes amounts equivalent to 12 beers a day but never gets intoxicated. It also consumes insects and small geckos, which it grabs with its mouth but also uses its hands to hold and move the food during consumption.