11 of the Smallest Mammals in the World

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Itty bitty fur balls

Photo: bluedog studio/Shutterstock

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

Small mammals can occupy ecological niches which 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, like this baby pygmy marmoset (pictured). Here's our list of some of the world's smallest mammals.

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Etruscan shrew

Photo: Trebol-a/Wikimedia Commons

There are a number of tiny shrews, but this pipsqueak takes the cake as the smallest. In fact, the Etruscan shrew is the smallest mammal in the world by mass. On average it weighs less than 2 grams, and has a body length of about 4 centimeters.

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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Jerboas

Photo: reptiles4all/Shutterstock

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

This ability is a great example of convergent evolution. Although jerboas may resemble miniature kangaroos, they aren't actually related to them. In fact, they are rodents.

The smallest species is the pygmy jerboa, which also happens to be the smallest rodent in the world.

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Bumblebee bat

Photo: Bob Cornes/Bedfordshire Bat Group

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 in at just around 2 grams, it's so small that you might actually 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 vulnerable, and a few roosting populations are at risk of extinction due primarily to human activity.

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Mouse lemurs

Photo: A.J. Haverkamp/flickr

These adorable creatures are the world's smallest primates, measuring in at around 27 centimeters in length including their tails.

The smallest species is the Madame Berthe's mouse lemur, which measures at just about 10 centimeters and weighs only about 30 grams, meaning it could easily fit into the palm of a hand. (Check out these pictures and videos of lurking mouse lemurs!).

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Least weasel

Photo: Bering Land Bridge National Preserve/flickr

This finicky, wise little weasel is the smallest species of the Carnivora order, making it the tiniest true carnivore in the world.

Weighing in at under 50 grams, It might be hard to imagine something so small being such a clever hunter, but the lesser weasel is the worst nightmare of any small rodent it encounters.

They are also known for having a "small person complex," often exhibiting a much bigger, more ferocious personality than their small size might suggest.

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Pygmy possum

Photo: Janelle Lugge/Shutterstock

Ranging in length between 5 and 10 centimeters and often weighing in at barely over 10 grams, these mini marsupials are found hanging upside down in trees in Australia and New Guinea.

They are so small and so difficult to spot that a new species of pygmy possum was just discovered as recently as 2007.

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African pygmy mouse

Photo: AleXXw/Wikimedia Commons

Mice are easily recognized by their small size, but the African pygmy mouse takes that trait to the extreme. Measuring at under 7 centimeters in length and often weighing less than 10 grams, it is the world's smallest mouse.

In fact, it is so small that it typically hydrates itself solely by licking dew off tiny pebbles that it cleverly stacks in front of its burrow.

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Pygmy marmoset

Photo: Dmitri Gomon/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 15 or 16 centimeters, and adults typically weigh under 140 grams. Therefore, their diet consists of insects. They also live a long time given their size, occasionally reaching ages in excess of 20 years in captivity.

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

"The beauty of genomics means that we can now see the pygmy marmoset is a term for two species which have been evolving independently for nearly 3 million years," said Professor Jean Boubli in Science Daily.

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Long-tailed planigale

Photo: Alan Couch/flickr

You might say that "planigale" is Australian for "small". These little guys, native to the land down under, are the world's smallest marsupials.

Their small size is exemplified by their flattened heads, which are typically one fifth as deep as they are wide. This adaptation allows planigales to squeeze into crevices and cracks any other mammal would find impossible. They weigh in at under 5 grams and reach lengths averaging under 60 millimeters.

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American shrew moles

Photo: Natalie McNear/flickr

The smallest species of mole in the world is the American shrew mole, a tiny mammal measuring under 5 centimeters and weighing only about 10 grams.

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.

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Tree shrews

Photo: Paul J. Morris/flickr

Not to be confused with the true shrews or elephant shrews, tree shrews are a group of mammals set apart.

In fact, they appear closely related to primates, though no clear fossil record of tree shrews exists. They've certainly got the brains to show for it; tree shrews have a greater brain-to-body-mass ratio than humans.

The smallest tree shrew in the world is the pen-tailed tree shrew, which can weigh as little as 25 grams and measure barely more than 10 centimeters.