[narrator] Growing up in the wild can be pretty hardcore.

Imagine learning to leap, roar, swim, or fly for the very first time.

You've got to get it right, because the faster you are, the stronger you are, or even the better you can camouflage yourself, the greater your chances of surviving and thriving in the wilderness, when you grow up that is!

But with all this feral rivalry going on, you've got to wonder, who really is Mother Nature's biggest or smallest or most dangerous untamed youngling of them all?

The answers will astound you, and we are counting them down from ten to one.

They are cute, they are "wild," they are the "cover girls and boys" of the animal kingdom and they know it!

They are baby animals.

When you think of the word "baby", you think "small", right?

Well, the ten babies that make up this particular countdown redefine what "small" means.

From the miniature to the minuscule to the microscopic, we are creeping quietly into the animal world's nursery to take a look at what it means to be teeny, weeny, and wild.

Kicking things off at Number ten is one of Australia's most iconic marsupials and one of the most unusual baby animals on the planet, the wallaby.

A baby wallaby, that's known as a joey, is not just tiny when it's born, it is also nowhere near ready to interact with the outside world.

Inside this pouch is a tammar wallaby joey which started out a couple of weeks ago the size of a jellybean.

This blind, hairless baby is able to do little else but drink milk and grow.

While this tiny wallaby joey gets on with the business of becoming independent, let's take a look at adult wallabies.

They're not just amazing creatures, they're quite small as well.

Wallabies can weigh anything from 2 to 24 kilograms, nowhere near the size of their bulky kangaroo cousins.

An adult male kangaroo will come close to 90 kilograms.

There are about 30 wallaby species living in the wild around Australasia, with slight variations in fur colour, size, and habitat.

Wallabies have slender noses, small claws, and petite ears that can swivel 180 degrees, to allow them to sense predators easily.

There is one thing about the wallaby that is big, their back feet.

And that's why they are classified in scientific literature as a macropod, the Greek word for "big foot."

"Macro" meaning "big" and "pod" meaning "foot."

And these big feet are very handy for wallabies.

Let's get back to our tiny wallaby joey.

When we last paid a visit, it was about ten days old, totally dependent on the safety of the pouch.

But now, around six months of age, with a thin coat of fur and a set of wobbly legs, it's time to take on the world.

Wallaby joeys are equal part brave adventurer and baby that needs its mummy.

While the world outside the pouch is endlessly interesting to a young wallaby, they use every minute of the year or so that they have access to their mother's pouch, to learn the ways of the wallaby, on their own terms.

Sadly, wallaby joeys sometimes end up in care at wildlife sanctuaries, finishing off their development inside a cloth pouch.

[kookaburra laughs nearby] To make sure these precious bundles grow up strong, they're bottle fed with special formulas.

Just like a wild joey, when they're big enough, these orphans enjoy their time exploring outside.

Eventually, these little ones will say goodbye to their humans and say hello to the other wallabies living at the sanctuary, their new family.

These yellow-footed rock-wallabies live in the east and south of Australia.

A rock-wallaby's feet are broad, flat and padded, allowing them to balance on arid boulder terrain.

Apart from their large grippy feet, the yellow-footed rock-wallaby has developed another impressive survival skill.

These desert dwellers can drink ten percent of their body weight in just a few minutes, which probably means they can burp their own names a little while afterwards.

[birds chirp] While some wallaby species are found in big numbers across the continent of Australia, there is one very distinctive wallaby that almost disappeared.

Between 1930 and the '70s, these bridled nailtail wallabies were thought to be extinct.

One day, a fencing contractor in western Queensland spotted a small mob of wallabies with distinctive waistcoat markings, and just like that, the wallaby, known by locals as "Flash Jack," was back on its way to a healthier population.

From the Australian outback to open grassy fields.

When you think "horse," "small" is not necessarily the next word that comes to mind.

Racing in at Number nine is an animal that takes those two concepts and squishes them into a tiny package with massive personality.

Meet the miniature horse.

An adult miniature horse must be about 8.2 hands or less tall which is "horse speak" for a little over 85 centimetres from the ground to the withers, which is also "horse speak" for between the horse's shoulder blades, near the base of their mane which, again is, you guessed it, "horse speak" for the flowing ridge of hair running down a horse's neck.

Foals, the term for horse babies, will stand up within about 40 minutes of their birth.

And they will be galloping within a day or so.

For most baby mammals, the milk they drink from their mothers is a vital food source.

But for foals, it's extra important.

That's because foals are born with a developing immune system.

They must receive antibodies from their mothers in the first hours and days after birth or they simply won't survive.

See how it's head-butting its mother's udder?

That encourages the milk flow.

Foals will feed from their mothers for between four and seven months, but they start eating grass and hay a couple of weeks after birth, though it may take them a while to work out what grass and hay actually is.

Some foals like to stay close to their mum.

Others are very curious about their surroundings.

But this pair are more adventurous, exploring the trees for more exotic greenery to munch on.

And when they tire of that, it's time to chew on each other!

When they're not testing their teeth out on their playmates, there are giant hay bales to tackle, and tails to practise swishing.

Miniature horses are officially classified as horses, not ponies.

This is because, like full-sized horses, miniature horse bodies are in proper proportion.

A pony is generally stockier than a horse, with shorter legs in relation to its body and a thick neck.

Miniature horses come in all the same colours and coat patterns as full sized horses.

And as you may expect, the horse world has some pretty cool words to describe a horse's colour.

A palomino is a horse's coat that appears to be yellow or gold, with a pale tail and mane.

This is a piebald mini: that's a black and white coat that looks like it's been painted.

And that white stripe down the horse's nose?

That's called a blaze.

[light music] The miniature horse foal is everything you could possibly love about a horse, in teeny tiny "bite size."

And speaking about tiny bites, they might be small, but mini foals are really big on annoying their mums, just like lots of other baby animals.

If this mare could talk, she would have one thing to say to her cheeky baby, "No!"

Which, in horse speak, is... [horse snuffles] [funky music] It's no secret Mexico is a land of extremes, with high mountains, deep canyons, and very small dogs.

[dog yaps] Because yapping its way into eighth place on our countdown is that Mexican superstar: the Chihuahua.

Small in stature, big on "attitude."

No more than 20 centimetres tall, no more than 2.7 kilograms, these round-headed, big-eared pooches are the smallest dog breed in the world.

As newborn pups, Chihuahuas can weigh as little as 70 grams.

That's around the same as an egg.

And there is no doubt that these puppies look cute enough to eat.

You could fit one in the palm of your hand.

But Chihuahua's grow fast.

By three months of age, this little pocket rocket is about one third of its adult weight, and 150 percent of canine cuteness.

[funky piano music] Chihuahua is a state of Mexico, bordering Texas and New Mexico.

Ancient Latin Mexican cultures had long loved tiny dogs, including them in rituals and ceremonies.

When American tourists came to Chihuahua, they were charmed by the tiny dogs, and locals started to sell them across the border.

And seriously, how could you resist?

Those eyes, the tiny paws.

[dog yaps] Oh, and the yapping.

[dog barks] Chihuahua puppies come in two coat types, long, and short, in a variety of colours and patterns.

There are two recognised head shapes in the breed: the deer head, that's the pointy nose pup.

And the apple head, the snub nose baby.

The fact that apple head Chihuahuas resemble human babies is thought to be one of the reasons why people find these puppies so attractive.

Being so very tiny, the life of a baby Chihuahua can be full of dangers.

Their lack of body mass makes them very vulnerable to changes in temperature.

Their tiny bones can be easily broken.

And in certain environments, Chihuahuas are commonly picked up by birds of prey in the same way rats or rabbits might be.

Chihuahua puppies are demanding.

Between birth and four weeks of age, their mother provides all the nutrition they need.

They have a very fast metabolism and require feeding around three to four times a day, which, when you're a Chihuahua mother, is pretty exhausting.

Lucky those little puppies are adorable from the tips of their ears to the end of their tiny puppy tails.

From the borderlands of Mexico to a creature that's from the rainforests of Brazil.

It is very hard to look at Number seven in our "Smallest Baby Animal" parade and not think of tiny humans at the kindergarten snack table.

This is the common marmoset, 250 grams of fruit, vegetable, and worm-eating New World monkey.

Living in a zoo, this baby marmoset might just have the best "baby life" of all.

[peeping sounds] [peeping sounds] [peeping sounds] Born into troops of up to 15 individuals, baby marmosets are carried on their mother's back for the first two weeks of life.

After that, the troop takes over.

While the baby spends some of its time exploring its home, as soon as it gets a little bit tired, or scared, there's a furry "family member" to leap onto and snuggle into.

And that same adult will act as a playground to chase your sibling around.

So, why are marmosets so helpful to each other when it comes to raising babies?

The key is in their size.

An adult mother marmoset weighs around 250 grams, and a baby around 29 grams.

Babies are generally born as twins, or sometimes triplets, which means a mother marmoset is carrying around over a quarter of her weight.

That would be like a human mother holding a ten-year-old, 24/7.

So, the rest of the troop steps in, making marmosets not just one of the smallest animals, but also the nicest.

But the time of piggybacking doesn't last forever.

When the babies hit the one month mark, they are gently encouraged to get off and start learning how to scamper along the branches for themselves.

Their claw-like nails help them hang on.

Being very small, marmosets are easy pickings for predators like tree snakes and owls.

To ensure they have eyes on all the possible predators, and enthusiastic babies, marmosets have developed a pretty incredible skill.

Their heads can rotate up to 250 degrees.

That is like a human being able to spin their head to see what's directly behind them, which we can't do.

Please don't try it out.

You are not a marmoset.

Marmosets are New World monkeys.

This is a class of primates mostly found in Central and South America.

Compared to Old World monkeys like proboscis monkeys, they are generally smaller, and their eyes, ears, and noses work differently.

But there is one thing all monkeys have in common, and it's the thing that defines monkeys from larger primates like gorillas, chimps, and humans, a tail.

And in the case of the common marmoset, that long, fluffy, striped tail is pretty adorable.

Marmosets share around 93 percent of their genome with humans.

And that has meant that they are intriguing to researchers and zoo visitors alike.

And a big part of that interest is in the similarities between humans and these miniscule monkeys.

Marmoset mums and dads are not just doting parents because their babies are cute.

Their social bonds are key to their survival, encouraging healthy hormones to flood their bodies and improve their well-being.

And seeing as we are 93 percent marmoset, we should probably remember that our families are pretty important to us.

Even when they're a bit annoying.

Sticking with animals that are only found in the Americas, Number six on our countdown manages to pack a ton of capacity into a spectacularly tiny body.

Welcome to the world of the hummingbird.

There are over 300 species of this remarkable bird, found primarily in North, Central, and South America.

And though they vary slightly in size from practically invisible to extremely small, hummingbirds all share one remarkable thing, wings that flap about 100 times faster than those of other bird species.

Hummingbirds start their lives inside petite nests carefully woven from twigs, moss, and spider silk.

These nests can be as small as a walnut, housing eggs that are around the size of a jellybean.

After two weeks hatchlings appear, and if you thought adult hummingbirds were small, the babies will blow your tiny mind.

These chicks weigh around the same as one single pea.

You can easily fit two of them into a bottle cap, though it would be very wrong to try.

Their feet are so small, they can't stand on them.

And so, the job of food delivery comes down to the mother hummingbird.

On the menu for an itsy bitsy bird is nectar and small insects caught, carried, and, eugh, regurgitated by the mama "meal service," up to three times per hour.

That's got to be exhausting.

While these babies digest one of their many meals, let's take a look at the extraordinary capacity of their parents.

Hummingbirds are believed to be the only birds that can fly backwards.

Not only that, they can hover for long periods, turn, and stop instantaneously.

They visit over 1,000 flowers a day and eat half their own body weight in sugar, daily.

There's barely time for a toilet stop for these busy birds.

But their hard work does mean they have a lot of food in those tiny bellies to expertly deliver to their ever-growing, but still ridiculously tiny, babies.

These hatchlings are demanding for a good reason.

They grow fast.

Within only a month, they will transform from tiny featherless chicks to fully independent, hovering, backwards-flying, beautifully coloured hummingbirds.

It's time to answer a question that must be buzzing around in your brain.

Why is a hummingbird called a hummingbird?

From the sound their superfast wings make.

In 2021, researchers set more than 2,000 microphones and high speed cameras up in front of six hummingbirds, and recorded the sound of their wings flapping.

What they found was hummingbird wings generate a sound that's 40 hertz.

That is at the very bottom of the human hearing threshold.

We don't call that sound a whine, or a buzz.

It is, in fact, a hum.

So, science proved that we got the naming of hummingbirds absolutely right.

When is soaring through the air not flying?

When you are Number five on our countdown, of course!

Meet the glider, a type of small Australasian marsupial that has mastered the art of taking to the air without the need of wings or feathers.

A glider is any one of seven species of small-pouched mammals that have a fold of skin between their arms and legs called a patagium.

As seen in this rare footage, when stretched out, the patagium acts like a sail that can carry them for up to 140 metres from tree to tree.

And make them look super cute while they're doing it.

But you haven't seen cute until you've seen a baby glider.

When it leaves its mother's pouch at around 10 to 12 weeks of age, a sugar glider will be about 35 grams, similar in weight to a light bulb.

[mischievous music] Joeys will spend another couple of months sticking very close to the nest and their mother until they're weaned.

Then, they turn their attention towards trying to glide.

Gliders are very social and live in colonies of up to seven breeding pairs.

Twin births are common.

And glider mothers have four teats, so can find themselves feeding multiple joeys at once.

In the wild, their territory can cover a hectare or more, about the same area as a baseball diamond.

So they have developed an ingenious way of staying in contact.

Gliders have scent glands that they use to mark trees, to let their family know where they have been.

There is one member of the group that is more of a loner, the incredibly fluffy greater glider.

These marsupials only come together to breed.

Like mini-real estate moguls, they can have up to 20 tree hollows in their territory, plenty of safe places to glide in and out of.

Gliders, because of their size and innate temperament, are delicate creatures.

As small tree dwellers, they are a tasty snack for birds, reptiles, and feral carnivores.

While many are omnivorous and will occasionally eat small lizards and insects, their main diet is fruit, flowers, and nectar.

In their natural environment, they are classified as important pollinators.

Gliders are, in essence, the tiny, furry spirits of the Australian bush.

Their capacity to manoeuvre through the air is quite impressive.

Key to this is the way they use their tail.

In the trees, it allows them to grip and balance but when a glider takes flight, their tail works with their extended skin fold to become a rudder, allowing them to angle their direction, moderate their speed, and adjust their landing gear for a safe arrival at their destination.

As adults, gliders range in size from 8 centimetres to 48 centimetres in length.

And their small size and adorable appearance makes them, sadly, a target for the pet trade.

Given what we now know about these small, forest-dwelling animals and their even smaller babies, surely the best place for them is with their glider families.

From a dainty wonder in the land "Down Under" to a pond near you.

In the world of small creatures, our next animal holds a special place for being small in three separate ways.

The frog.

The tiny shape-shifter of the "Small Baby Animal" business.

[croaking] There are thousands of species of frogs on planet earth, on every continent, except Antarctica.

If you look in the right place, you will find a frog.

Actually, lots of frogs.

Because when it comes to baby making, most frogs do things on a large scale.

There's a bit of variation around frog reproduction but, generally speaking, the frog "nursery story" goes like this.

The first stage of a baby frog's tiny life generally starts on the surface of still water, with fertilised frog spawn.

Each jelly-ish floating egg takes a couple of weeks to grow and change into its new form.

As long as the conditions around them stay moist, tadpoles, also referred to as "polliwogs", hatch out of their eggs, complete with a working set of gills and a small fish-like tail.

Over the next few months they swim around, feeding on pieces of aquatic vegetation, small invertebrates, and micro-crustaceans.

As they grow, the process of metamorphosis takes over, slowly transforming the tadpoles.

First, the back legs grow in.

Then, as the front legs appear, the frog's internal structure changes to accommodate lungs that it starts to use to breathe air.

In addition, the tail drops off and the tiny young frog is ready to walk on land.

But frog development is not all a "good news" story.

In all its forms, the frog is small relative to its predators.

Fish, birds, and small mammals are all happy to suck up an egg, a tadpole, or a froglet in their daily food search.

Sadly, the majority of frog eggs will not make it all the way to adulthood.

Let's take a look at a real frog success story: the southern corroboree frog.

This tiny, moss-dwelling amphibian was once found in massive numbers across the south-eastern Australian alpine region.

In the late 20th century, climate change, introduced species, development and disease, have caused catastrophic changes to the corroboree frog population, to the point where they were declared "critically endangered."

But as part of a National Recovery Program, breeding centres were established and are now successfully returning colonies of corroboree frogs into the wild.

Frogs and their tadpoles might be slimy and they might make you feel a little bit like going, "Eugh," but it is worth remembering that they play a crucial role in balancing our environment.

And this is because frogs and tadpoles love the things we hate.

To frogs in all stages of their development, flies, mosquitoes, all the pesky insects, are "five star dining."

So, unless we are happy to be overwhelmed by insects, frogs are most definitely our friends.

We're into the top three smallest beasties now, and while amphibious frogs straddle the realms of land and water, Number three on our list is a master of marine camouflage.

The cuttlefish.

A cousin of the octopus.

With eight arms, two tentacles, a bony beak, and a face that only an alien could love, cuttlefish are the very definition of curious-looking creatures.

All cuttlefish can use their bodies like a living canvas, on which they display their most impressive skill: metachrosis, which is the scientific word for "colour change."

Like their squid and octopus relatives, cuttlefish have special pigment cells in their skin called chromatophores.

In response to, say, a threat they can instantly control and contract these cells to change their colouration and camouflage themselves.

One of the smaller members of the family is the Flamboyant cuttlefish, named for its bright colours and frills.

These cuttlefish are also one of the most toxic marine creatures, their muscle tissue being highly poisonous.

But even noxious creatures make babies, and that's exactly what this Flamboyant cuttlefish is doing.

The fertilisation of cuttlefish eggs takes place in the mouth of the female.

She then deposits her babies in a safe place.

In this case, this mother has chosen a coconut shell where they will sit for a matter of months while they develop.

And when they hatch, the baby cuttlefish emerge with a full display of their stunning colours.

Scientists believe that cuttlefish are exceptionally smart.

In a 2021 study, scientists discovered that cuttlefish have extraordinary memories.

Cuttlefish can remember exactly where they found food, and use this information to return to that site for repeat meals.

It was also reported they have great self-control and will refuse food if they suspect something better is on its way, which seems smart, 'cause who's going to turn down a better snack?

Apart from the Australian giant cuttlefish, no species of cuttlefish is officially listed as "near threatened."

It is believed that the relative prosperity of the cuttlefish is down to one reason.

Unlike their cephalopod cousins the octopus and the squid, most people aren't that interested in eating them.

And while that's good news for the cuttlefish, it should probably give us humans a reason to reconsider the way we treat our marine animals.

If you need another reason to love cuttlefish babies, consider this.

A joint Taiwanese and French study recently discovered that when they are inside their eggs, not yet fully developed and completely defenceless, some species of cuttlefish are smart enough to stay still if a predator comes near.

Who's a clever cephalopod?

OK. From the miniature horses of the Old World to the New World's most miniscule monkeys, plus Australia's tiniest airborne mammals, we've applied our magnifying glass to eight of the smallest creatures on earth.

Which now brings us to our Top two "Smallest Baby Animals."

And if you have a problem watching arachnids doing what arachnids do, maybe close your eyes and just listen for a while.

Because scurrying in at Number two is the Redback spider.

They are definitely small.

And their babies are very small.

But they can also be very, very dangerous.

Getting up close and personal with these guys through a TV screen is probably as close and personal as you want to get.

We are going to stick with the females today because, like with a lot of spider species, the female Redback spider is bigger and more spectacular.

And she's the one that is most involved with the babies.

Here's where the baby part of the Redback story starts.

A mother Redback, recognisable by her black colouration and distinctive red stripe, can carefully and skilfully create up to ten egg sacs in her breeding cycle.

Each of these sacs, usually laid within the mother's messy web, contain... wait for it... up to 250 eggs.

That's potentially 2,500 Redback spider babies on the way.

Redbacks are urban creatures, so it's not unusual to see egg sacs hanging in and around people's homes.

All the Redback mother cares about is that her "nursery" is set up somewhere warm and sheltered, with good food supplies.

Over two to four weeks, the sacs turn brown and may loosen in structure, and these are the signs that a spidery birthday is imminent.

And here they come, baby Redback spiders, lots of them.

Paler than their parents, with grey and white mottling on their abdomens, the spiderlings crawl from the sac and start their search for food.

But not before they turn on their weaker or unhatched siblings for a quick first meal.

It will take these spiderlings around four months to reach maturity.

In spider terms, this means that's the time they have reached adult size and can start breeding.

But just in case you were wondering, we suggest you leave Redback spiders of all sizes very much alone.

Fun facts about Redback spiders.

Female Redbacks are ambush hunters.

Those messy webs are totally deliberate, woven with hidden lines to catch unwitting prey.

And if the trap doesn't work, Redback spiders can live for a really long time without a meal.

Spiderlings can last for up to 160 days.

Towards the end of this time, the spiderling will get sluggish and slow.

But amazingly, one feed is enough to revive the spiderling completely.

Bet that makes you feel better about this huge swarm of baby Redbacks.

OK. Let's leave dry land behind and dive into the ocean and really get to know our Number one "Smallest Baby Animal," the clownfish.

The first thing we need to clear up is that the name "clownfish" is actually an umbrella term for around 28 species of anemonefish.

They have this name because they choose to live in anemones, a deceptively unpleasant home.

Most marine creatures will get a nasty sting if they touch an anemone.

But clownfish and anemones have what is called a symbiotic relationship, which means clownfish have a safe place to live and in return, anemones get fertilised by clownfish poo.

There are a lot of theories about why most clownfish species are able to survive anemone life but the currently accepted one is that clownfish are coated in thick mucus that protects them.

So much so that some species actually sleep deep inside the anemone, right on top of its mouth, and no midnight snacks are had by anyone.

But enough about stinging marine animals.

Let's get into the clownfish baby zone.

Because if you think the adults are small, saddle up.

Baby clownfish are even cuter than a Hollywood film can make them.

This male is fanning his family, this clutch of tiny red eggs, keeping the oxygen supply up to his teeny tiny babies.

And don't worry, he isn't biting the eggs, he's just keeping the nursery tidy.

It turns out, male anemonefish have a high level of a hormone very similar to the same chemical that drives human parenting.

And scientists at the University of Illinois discovered that if they deprived the male clownfish of that hormone, called isotocin, then their super-parenting instincts completely disappeared.

Clownfish fathers might be extraordinary, but it's the females that rule the roost.

The females are generally bigger than the males and these ladies make the rules.

The one breeding female has all the nearby males competing for her attention.

Only the strongest male is chosen.

And if the dominant female dies, her mate morphs into a female and becomes the "queen of the anemone."

This adaptation is one of the reasons why most clownfish populations continue to thrive.

Clownfish lay a lot of eggs, anywhere between 100 and 1,500 at a time.

They are capable of spawning every two weeks.

And the eggs hatch around ten days after they are fertilised, depending on the temperature of the water.

After a short larval phase, baby clownfish graduate to a nursery, where they hang out with other juveniles, until they have mastered the art of clownfish life.

And can take their opportunity to build the next generation of clownfish safely among the anemones.