Original subtitles

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At the best of times, the animal kingdom is a harsh place.

But for some, harsh would be a welcome respite

for victims of these predators,

because they are cold-blooded killers.

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Snakes.

Silent and still.

A prey approaches and they strike.

They are one of the most stealthy,

deadly hunters on the planet.

Great hunters need great camouflage.

For snakes that means colored scales.

These scales not only offer the snake protection,

but they have evolved into a crucial tool for hunting,

especially for vipers, rattlesnakes and adders.

They've got a -- what they call a rough or keeled scale,

which doesn't have that glossy shine to it.

It's almost a matte color

that allows them to blend in perfectly

to the natural environment

allowing prey to wander close enough

within the range for them to strike out and grab a hold.

To hold that prey in place,

snakes are equipped with needle-sharp, hollowed-out fangs

that can amazingly replace themselves at need.

If one of the teeth are broken in a strike,

that tooth would be shed out and replaced with a brand new one.

Even a snake's gums play a special role

by keeping those teeth nice and sharp.

The teeth are also covered by a protective layer, gum,

which keeps the teeth precision-sharped all time,

because they need that.

They can't have blunt teeth because they rely so much on it

like precision of a hypodermic needle.

The size and position of a snake's teeth

differ according to the species.

In the case of the cobra, their teeth are small

and are located at the front of the mouth.

They're called front-fixed fang snakes.

So their fangs are always erect.

When they bite,

the muscles contract around the venom glands,

forcing it through the venom duct,

through the fang into its prey.

And in the case of the viper, its teeth are long and lethal.

Those guys have got enormously long fangs

that lay flat along the roof of the mouth.

When they strike out, the mouth will open.

The fangs will swing into place.

They will bite them into the prey.

But the teeth are just the tip of the iceberg.

The snake's ultimate marvel of design is its deadly venom.

Venomous snakes, they have adapted this way

of being able to kill and immobilize prey.

Clear or slightly yellowish,

snake venom is a highly developed type of saliva

that's stored in glands behind the snake's eyes.

When a snake bites,

muscles around those glands squeeze out the venom

through the hollowed fangs

and into the unfortunate recipient.

Over time,

snakes have developed 3 unique types of venom.

3 very different, but very deadly weapons.

Different snakes have varying compounds

in a range of proportions.

Some venoms work very, very quickly.

Some tend to work slower.

Each venom works differently

on different parts of the body as well.

So you have things like hemotoxins that work on blood.

You have things that are cytotoxins

that work on blood and tissue cells.

You have neurotoxins that affect the nervous system.

But before snakes can bite their victims,

they have to find them first.

Snakes come very well-equipped for tracking down prey.

They don't have an external ear,

but an internal ear allows them to detect

low frequency sounds, motion and sound waves

traveling through the ground.

Snakes also have an incredible sense of smell,

thanks to a forked-tongue

that can pick up minute scent particles in the air.

As they pull the tongue in,

they wipe it over an organ in the roof of the mouth,

called the Jacobson's organ,

which is a spiral nervous system connected to the brain

sending messages through,

telling them what they're smellin'.

Some spices, like vipers, even have an infrared sixth sense

designed to pick up a prey's heat signature.

They have heat-sensitive pits around the upper lip

that tell them what size the prey is,

where it is and how far it's away from them.

When the prey has been captured and rendered powerless,

it's time to chow down.

Nothing goes to waste.

The snake will come and find the head of the prey

and start to swallow it from the head first.

They'll push it down to the stomach area,

where digestion will then take place.

So what happens is everything gets broken down

except for anything made of keratin or enamel.

So the hair, the nails, the teeth of the prey

will come up.

Their special jaws allow them to eat animals

much bigger than themselves.

But then their lower jaw is made up of 4 bones,

which gives them elasticity to stretch really wide apart

and then use those jaw bones

to independently hook into the prey

and walk it down the throat.

A venomous snake can take as much as 9 hours

to digest its victim.

But not all killer snakes are venomous.

Some like boas, pythons, and anacondas

have been designed to literally squeeze the very life

right out of its victim.

Every time the animal exhales the snake tightens.

Exhales and it tightens.

And eventually the animals can't breathe in.

And a large number of the time

what actually kills the prey is a heart attack,

because of the shock and adrenaline

that are going through.

They have been around for so long that no one can quite agree

when snakes first stalked the Earth.

But in that time,

they have evolved perfect camouflage,

deadly fangs, specialized venom

and infrared and motion-sensing abilities.

The result is a group of predators that is peerless.

A true snake in the grass.

Some predators make a kill with dramatic flair.

But tarantulas...

...they just scuttle in and get the job done.

They're the stuff of nightmares.

Long hairy legs.

Fat bulbous body.

Sticky web.

Deadly venom.

Of the several thousand species of spiders in the world,

tarantulas are the most dreaded of all.

A creature to be avoided at all costs.

They're found more or less around the world

in tropical and subtropical regions

such as in Central and South America,

Africa and Asia.

Measuring up to a foot-long,

the Goliath bird eater is the heaviest tarantula

on the planet.

While as it name suggests,

it does sometimes go after the chicks of ground-nesting birds,

it will more often go after anything that moves

as long as its small enough.

Anything that is up to their size.

Insects, small rodents, frogs, lizards,

whatever they can get.

Just like the Goliath bird eater,

the Brazilian salmon pink bird eater's name

is also misleading.

It only seldom eats birds and never ever eats salmon.

The hairs on their body have sort of, a rose-pinkish color

and that's where they get their name from.

These small distinctions aside,

most tarantulas share one important thing in common.

They are all highly-skilled ambush predators.

Like all spiders, this tarantula can spin silk web

from specialized structures in its abdomen called spinnerets.

But unlike most spiders,

it doesn't use that web to actually catch its prey.

In fact, the silk is mostly used for

the construction of their own nests,

whether it's in the tree or in an underground burrow.

These are not simple structures.

While building their elaborate nests,

some tarantulas use this silk

to set up a built-in home alarm system,

invisible silk trip wires.

If anything walks into its burrow,

it sets off the trip wires and lets the tarantula know

that a meal has just walked through the door.

The tarantula will hide and wait for the prey

to come close and then jump in.

And it does all that without the benefit of vision.

Tarantulas have 8 eyes,

but they can't see worth of beans.

They just distinguish between light and dark and some motion.

They're not really capable of forming images

and to see depth perception, per se.

While tarantulas may not be able to see their prey too well

with their eyes,

the hairs all over their body make up for it.

These hairs are actually organs

used to sense the world around them.

The hairs on their bodies are highly sensitive,

innervated in that they're are able to detect

slight movements and vibrations

that they maybe sniff around them in an environment,

such as if a prey is scurrying along in the leaf litter,

they will detect those vibrations

and know that it is likely to be a potential prey.

Tracking prey is one thing, bringing it down is another.

This Goliath bird eater's main take-down weapons are its fangs,

which can measure up to an inch long.

Their fangs are hollow.

They're connected to venom glands

and they pump up full of venom, which paralyzes the prey.

Like most spiders,

the Goliath bird eater can't chew.

Its mouth is designed for sucking up liquid food,

which means it has to turn its prey into a smoothie.

They do so by injecting powerful venom

through appendages on the side of their mouth.

They're, kind of, like fangs known as chelicerae.

These chelicerae inject powerful venom

that essentially liquefies the tissues of their prey,

putrefying it, liquefying it into a slop

that can then be sucked up into the mouth parts.

This tarantula, like all spiders,

is also equipped with rigid body armor,

an exoskeleton that protects its internal organs from damage.

As it grows, this tarantula continuously moults,

shedding its old exoskeleton

and replacing it with a larger one.

But with the predator is at risk of becoming prey,

it's got a trick up its sleeve.

The body of the tarantula is covered with bristles

that are called urticating hairs.

They're little barbed hairs

and they'll throw them at their attacker

and they cause irritation.

The bald spot on this tarantula's abdomen indicates

that it's flicked off its fair share of stinging hairs.

Whether attacking or defending, with all their weapons,

tarantulas are sure to deliver a hair-raising experience.

Usually an encounter with this blood-sucking predator,

results in a nasty itch.

But sometimes it can literally suck the life right out of you.

Mosquitoes, not just pesta, but killers.

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They have been around for more than 30 million years.

Of all the dangerous animals in the world,

none has killed more humans than the diminutive mosquito.

In the wild, this mosquito can live at best a few weeks.

Its life would be even shorter

if it falls prey to a long list of predators,

that include birds, fish and spiders.

Life is short, so mosquitoes must breed quickly.

And for that they need our blood.

With mosquitoes, the male is harmless.

It's the female we have to worry about.

The female mosquito is our arch-nemesis.

She's the one who goes out and does all the blood-feeding.

They feed in order to get the blood

and from the blood they get protein

and from that protein they actually make their eggs.

When she's ready, the female lays her eggs in standing water.

She takes the building blocks of the proteins

from the blood meal

and she makes them into egg proteins of her own eggs.

And those egg proteins then help the developing embryo.

The eggs soon turn into larvae known as wrigglers.

Moving up and down in the water column,

these wrigglers breed through a small siphon

located at the end of their tail.

So they'll actually move up to the surface of the water,

make connection with the air through that respiratory siphon,

get the air that they need and then they release

and go back down into water column.

The larvae eventually become pupae.

And then the pupal stage,

which looks like a little comma, it does no more feeding.

It can swim around, it can breathe,

but it does no more feeding.

After growing into pupa, the mosquito emerges, at last,

like a butterfly would from a cocoon.

After the mosquito undergoes this metamorphosis,

males will go on to feed on plant nectar

until they mate and die a few days later.

But the female will immediately go on the hunt for blood

to produce eggs as quickly as possible.

She is now in full-attack mode.

To zone in on her prey,

the female mosquito relies on 3 key sensors:

chemical, visual and heat.

With her chemical sensor she zeroes in on humans

and some animal species with a healthy blood supply

by tracking what they release when breathing.

And so she'll detect that plume of carbon dioxide

and will fly upwind

towards the source of that carbon dioxide.

A female mosquito is able to detect contrast in color

and between foreground and background.

The more the prey moves,

the more easily she will find it.

And finally she uses her sensor to detect a heat signature.

She wants to make sure

it's a nice, living, breathing host to feed on.

All that's left for her to do

is to stick in her proboscis and bite.

The proboscis on a mosquito is what she uses to bite you with.

So there are 2 major hollow tubes within the proboscis

made by the stylets.

One of these tubes is for sucking up the blood.

The other is used to spit saliva into the skin of her victim.

She actually spits into you

an anticoagulant and an anesthetic

so that you don't feel the pain

and also your blood doesn't clot.

If she were to try sucking up blood

without using her special anticoagulant saliva,

the victim's blood would clot and plug up her mouth.

It's that special saliva

that causes the swelling and itching.

Most female mosquitoes have only one blood meal

in their short life before they mate and lay their eggs.

But some have 2 blood meals and reproduce twice.

This is where things get potentially deadly.

When they take their first blood meal,

they can ingest all sorts of parasites

or viruses or bacteria.

So if a female is lucky enough to get a second blood meal

and she picked an infection from the first blood meal,

that's where we're in danger.

That in that second blood meal,

she can be spitting out the virus,

let's say, to the new host.

Pathogens like malaria and West Nile virus

and for humans, things could get much worse.

So climate change is going to affect

mosquito-disease transmission everywhere.

Because as climate changes,

mosquitoes are able to expand their ranges

normally from southern areas, where there are more diseases,

up to northern areas,

where there aren't so many diseases.

And they'll bring those diseases with them.

For more than 30 million years,

the mosquito's adaptations and strategies

have ensured its survival

and have transformed it into a prolific killer of humans.

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A monster from the Middle Ages...

A vicious predator from ancient Greece...

The highest-ranking animal in Chinese mythology

representing power and majesty.

At a mere ten feet long and 300 pounds

Komodo dragons might be a bit smaller

than the creatures of lore,

but they're still vicious predators.

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The largest living lizards of the world,

they're actually a type of monitor lizard,

but got their name after a rumor started swirling

that a dragon-like creature

was living on the Indonesian island of Komodo.

When explorers first discovered them in 1910,

the name stuck.

They look like a dragon.

Big shoulders, big stalking neck,

long sleek head.

They have their long-- like, kind of, like vultures,

long cylinder heads that they can get inside of bodies,

you know, eat the carrion, get the meat, rip it out.

Really sharp claws used for digging,

ripping meat off the bones.

A very long powerful tail they use in combat.

Also to get away from predators.

They have extremely strong whipping power

and they're just very stocky made-for-all-terrain animals.

They're so aggressive and so powerful,

Komodo dragons can bring down animals

much, much bigger than they are,

like deer, pigs, water buffalo and even humans.

They're usually solitary hunters

but can team up to take down a particularly large kill.

They can run very fast in short bursts,

up to 11, 12 miles an hour, you know, on a sprint.

But they can't sustain that very long.

So what they would do is

usually they will kinda hideout, wait,

you know, by a bush, by a tree.

When prey would come through,

usually grab it low by the feet.

You know, kind of, drag it down.

Until recently,

they were widely thought to kill prey by poisoning them.

In truth, their victims succumb to blood loss

from their wounds.

Then, this fierce predator moves in to finish the job.

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With their long tongue flicking in and out of their mouths,

they collect air and deposit it on receptors

on the roofs of the mouths.

This helps Komodo dragons

smell prey from up to five miles away.

Komodo dragons devour hair, bones, hooves, horns

and all indiscriminately.

They're very opportunistic.

So whenever they do make a kill, they do find some food,

they can eat up to 80% of their total bodyweight in one sitting.

And then they may not be able to eat again

for another week or two,

depending on when they can get their next meal.

So they basically stuff themselves as much as they can

on everything they can while they can

and then from there they move on to their next meal.

They've been living on these Indonesian islands

for thousands of years.

Working their way up to the top of the food chain

and showing that they've truly earned the name

and the legacy...

...of the dragon.

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From our point of view,

these predators are living nightmares.

Brutal, savvy, program killers.

But from their point of view,

it's just another day at the butcher's counter.

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