11 Animals that are Super Small at Birth

Baby blue whales are a ton of fun—literally. The giant newborns typically tip the scales at a jaw-dropping three tons at birth. (If you want to visualize how that stacks up to a full-grown whale, it’s about the same size as an adult whale’s tongue.)

Whale babies easily dwarf their competition in the big baby world, but that doesn’t mean they're any more charming or special than even the smallest of newborns. Pound for pound (or ounce for ounce, as the case may be), the animal kingdom’s littlest newbies are still pretty wonderful in their own way.

1. Kangaroos

The marsupial birthing process is positively insane, but it’s also one of the most miraculous in the wild world. Baby kangaroos—you know them as joeys—only gestate in their mother’s womb for about a month. After that period, they are technically born, yet they emerge blind, hairless, and only about an inch in length before crawling into their mother’s pouch (called a marsupium) where they finish developing and growing for up to 400 days. After that time, they pop out of the pouch and look like what we’d expect a joey to look like, all furry and cute, even though they first entered the world looking like a piece of bubble gum.

2. Honey possum

Elsewhere in the marsupial world, the honey possum is believed to be the smallest mammal at birth. Baby honey possums only weigh about 0.005 grams when they are born, eventually completing their gestation inside their mother’s pouch to reach a hefty 2.5 grams by the time they’re ready to venture out on their own.

3. Pygmy seahorse

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The pygmy seahorse remains pregnant for approximately 11 days, after which the offspring are born by way of the male contorting his body in order to eject the tiny babies—each between 7 and 12 millimeters in size—from his pouch, sending them on to embark on their own adult lives. But poor papa doesn’t get much time to recover from his postpartum depression; it is not uncommon for the female to gift the male with another clutch of eggs as soon as 30 minutes after he’s expelled a brood.

4. Pygmy mouse lemur

Photo courtesy of Joachim S Muller, used under Creative Commons license

Another pygmy baby, the pygmy mouse lemur, also barely makes a dent on the birthing scales. Already the world’s smallest primate, pygmy mouse lemurs only grow to weigh about an ounce when they are adults, so it should come as no surprise that they are born only weighing about .45 gram.

5. Pygmy marmoset

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Pygmy marmosets are the world’s smallest monkey species, so their young are also quite wee. At birth, pygmy marmosets weigh about 15 grams each, and are typically born in pairs (though it’s possible for triplets or just a single birth to occur).

6. Etruscan shrew

The Etruscan shrew has the distinction of being the world’s smallest mammal by mass only (if we’re measuring by skull size, the bumblebee bat is the smallest). Adult Etruscan shrews only grow to about 4 centimeters in length (this doesn’t include their tiny tails, which can be as long as 3 centimeters). Baby shrews gestate for about four weeks, and are born in litters that can be as small as two cubs and as large as six. When they enter the world, they only weigh about 0.2 grams, and they can grow to be as large as 2.5 grams in maturity.

7. Bee hummingbird

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The bee hummingbird is the smallest bird in the world, so its young are appropriately tiny. As adults, they weigh somewhere around 2 grams (about the same as a penny), and babies hatch from eggs roughly the size of coffee beans.

8. Brazilian gold frog

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The Brazilian gold frog is the second smallest frog in the Southern Hemisphere, with adults clocking in at 9.8 millimeters in body length (not counting splayed-out legs). At hatching, baby gold frogs weigh a fraction of their adult counterparts, though a precise amount is currently unknown.

9. Pudu

Although the southern pudu is the more distinct of the pudu pair, it’s the northern pudu that clocks in as the world’s smallest deer. As adults, they stand about 13 inches tall, and rarely weigh more than 13 pounds. Baby northern pudus usually weigh in the 23 to 35 ounce range, and it’s extremely rare that infant pudus that weigh less than 21 ounces live.

10. Paedocypris carp

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Believed to be the world’s smallest fish species, the Paedocypris carp only grows to about 7.9 millimeters. Much like the tiny gold frog, it’s nearly impossible to guess how big the little carps are when they hatch, but they’re expected to also be the smallest fish babies on the planet.

11. Pink fairy armadillo

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The pink fairy armadillo, an Argentinean native, is the smallest kind of armadillo, special not just for its tiny size but also its puffy fur. Adult pink fairies are about 4.5 inches long (not including their tails), and they are all prodigious diggers. Baby pink fairies are born weighing about 3 or so grams before growing into a chipmunk-like size.