Nature

They're our planet's first builders,

nature's architects and engineers,

crafting homes of spectacular design

in every corner of the globe.

Some are elegantly simple, others surprisingly complex.

So it looks like a teenager's bedroom from the outside,

but if you were to cut this

right down the middle and look inside...

Whether they were made by beaks or paws,

these homes have a universal purpose --

to keep their owners safe

from a dangerous world

as they give birth and raise a family.

It makes it a perfect bear home.

It's secure, it's dry.

And it turns out that the quest for real estate in the wild

is all about the same three things we value most --

location, location, location.

A strategic location in space...

At a precise location in time...

These are the essential must-haves

of just the right home.

It looks like an ideal place to live, doesn't it?

The valley of the Snake River --

Jackson Hole, Wyoming.

t features beautiful Rocky Mountain views,

plenty of running water,

and a good mix of trees and shrubbery.

It's the perfect spot to build your dream house

and to commune with nature.

The surprising thing is,

much of what you see here isn't exactly natural.

It was shaped and crafted by a rodent --

the beaver.

This is where a family of beavers is making its home.

The dad has been homesteading here for nearly a decade,

and he and his mate have a couple of kits.

Their ancestors have been

working this area for thousands of years.

For this family, like all homeowners,

location is crucial.

For once they chose this spot, they set about

giving it a complete makeover

to meet their exacting specifications.

I'm Chris Morgan.

I'm an ecologist and I'm fascinated by

how animals construct their homes

and why they decide to live where they do.

There he is.

There's our inhabitant.

Beavers are very choosy about where they build.

There's one thing no beaver can do without.

It's top of the list in their real-estate requirements,

and that's a stream.

When beavers hear the sound of running water,

they feel compelled to build.

But before they start work on their house,

they first build a dam.

And check out this dam.

It's amazing! It's huge!

Beavers are the only mammals besides humans

that construct dams

to block water.

And they build big ones.

A beaver dam can be hundreds of feet long,

and it's strong enough to support me.

It is such an impressive construction.

I mean, look at this. It's packed with

big logs down to these tiny twigs,

and every single of of them -- look --

has been chewed off by a beaver.

These are all different building materials,

and one of the most impressive to me is the fact that

these beavers will swim with and push and hoist

these giants rocks -- look at the size of that --

right onto the top of the dam.

And they use these big rocks as anchors,

along with the giant logs,

and then they intersperse it with mud and grass

and other debris -- look at that, perfect --

and create this watertight system

with one idea in mind, and that is to

bring the water level up behind this dam.

And the difference between

this water level and that water level

is approaching, I'd guess, three feet.

It's quite something.

These beavers are not only designers and architects,

but stonemasons, woodworkers, builders.

They do it all.

The dam converts a stream into a pond.

Wow.

That's just the place to live if you're a water-loving,

web-footed beaver

who's much better at swimming than walking.

Now that the pond's nice and deep,

the beaver family instinctively shift gears

to start working on their house -- the lodge.

With all this construction work, they need a lot of wood.

Fortunately, their ancestors evolved into lumberjacks,

and they work the night shift.

Since the tender

inner bark of trees is a beaver's favorite food,

they can harvest a crop while they gather lumber.

Watch out!

But there is a limit to how much they can drag,

so our clever beavers let the water do the work.

When you think about it, it's really not a stretch

to call these guys hydro-engineers.

So they'll excavate these channels.

Look at this. They've actually dug the mud

out of this with their front paws.

They'll float these big logs out,

back to where the dam is and where the lodge is,

and it allows them as an aquatic mammal

to swim up these channels and access the new trees.

What an awesome system.

By damming the stream so it floods its banks

and then digging a network of canals,

the beavers have devised a way to swim right into the forest

to reach more trees.

It's a watery world.

And through their efforts,

they've also reshaped the entire neighborhood,

transforming a woodland into a wetland.

Of course, beavers don't work from a blueprint,

but they certainly seem to have one in mind.

And since this pair has built dams and lodges before,

their instincts are bolstered by experience.

This is the heart of it all,

the heart of the beaver neighborhood.

Look at the size of this.

This is the lodge.

My goodness.

It looks like a total jumbled mess of logs,

kind of like a volcano of logs.

They've stripped off the bark and eaten the inner bark.

Look at those teeth marks.

And then they use their food, the food waste,

as building material, so it looks like

a teenager's bedroom from the outside,

but if you were to cut this right down the middle

and look inside...

You'd see just how complex it is.

This lodge is build up against the pond's shore,

but the entrances are underwater for security.

Above is a suite of rooms.

Amazingly, the beavers actually carve them from the inside,

chewing and clawing their way through

that solid mound of wood and earth.

There's a kind of a mud room, where they can dry off,

and a family room, where they eat and sleep.

They left the domed roof a little loose

to vent out CO2 and to let in fresh air.

And as a finishing touch, they'll excavate the mud

on the shore side to create a moat

so their home will be completely surrounded by water.

Beaver lodges are all built around the same general lines,

but each one is unique,

a designer home that's perfectly matched to its surroundings.

The goal is to have a house that's cozy and warm,

safe and secure, where they can raise

their young ones -- in fact, the same things

that motivate every house-building animal.

But finding just the right location to build in,

that's the challenge.

Most animals can't do what beavers do.

They can't alter their neighborhood

to meet their needs.

So they have to make the best use of their habitat,

taking advantage of whatever nature offers.

This red-faced warbler has found a convenient spot

to raise her family --

right on the ground,

tucked away under a fallen branch.

The warbler's neighbor, a brown creeper,

takes an entirely different approach.

It climbs straight up a tree trunk

to hide its nest inside the bark.

And these house finches

make their home among the spines of a cholla cactus.

That's like putting up a barbed-wire fence

to keep out trespassers.

Of course,

the conditions where you live help determine

where you put your home.

A great desert skink escapes the searing heat

of the Australian Outback

by digging a network of underground tunnels.

Down here, it can be nearly 40 degrees cooler

than up on the surface.

A gopher tortoise makes its home underground too

because the pine forest it lives in is prone to fire.

No matter where you make your home,

your surroundings are bound to present

both challenges and opportunities.

A good homemaker knows how to deal with both.

The salt marsh sparrow makes its nest,

not surprisingly,

in coastal salt marshes from Maine to Virginia.