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Carpenter,

2
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lumberjack,

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surveyor, architect,

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stonemason, hydro-engineer...

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Man and beaver -

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two of the most skilled
and industrious creatures on earth.

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In a battle of construction,

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who really deserves the title
'Master Builder'?

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The first contender for the title
'master builder'

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is a dog-sized rodent found throughout
the rivers and lakes of North America.

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Beavers live and work in small,
multi-talented teams.

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This seven-year-old female
is the foreman of a family gang,

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which includes her male partner
- as builder's mate

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- and three adolescent apprentices.

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Here, in the Rocky Mountains of Wyoming

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they've got 6 months before winter arrives.

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In that time they'll create a pond,

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dig a network of canals,
clear acres of trees

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and construct a lodge with adjoining
larder, using only local materials.

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The beavers' toolbox includes claws
with a vice-like grip

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＃ chisels for teeth,

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highly tuned ears and eyes
for health and safety...

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and a pair of dextrous paws.

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A beaver is a green machine 每
fuelled by low-grade cellulose.

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Its broad, flat tail is a rear engine
that may run non-stop for 20 years.

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It works efficiently
on land and underwater,

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and webbed feet deliver
extra thrust for heavy loads.

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Down the valley are the other contenders
for the construction crown.

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They too have their work cut out
to finish before winter.

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They too have a blueprint
for a log cabin development.

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But their toolbox includes a 20-ton crane,

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a mechanical lumberjack

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and a hydraulic-assisted forklift truck...

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not to mention diesel-powered
caterpillar-tracked excavators

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and a 500 horsepower earth mover.

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Their expert team is made up of surveyors

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haulage experts, lumberjacks,

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carpenters and stonemasons.

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They've started laying the foundations for
the first stage in the building process.

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Upstream among the cottonwood trees,

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the beaver crew have also started
Stage one 每 constructing a dam.

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They pile up stones and rocks to form
a wall and cover it with woody debris.

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The foreman and her family
add more and more layers

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and over a couple of weeks
the stream is blocked.

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Water backs up behind the dam
to form a pond.

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It's just the first stage
in their 6-month schedule.

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Each day a busy beaver can
shift 10 times its own body weight

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每 a total of around 500 pounds.

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The beavers excavate
the bed of their new pond,

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making it deeper and using the mud like
mortar to plug any holes in the wall.

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Powered by strong hind legs
and chunky forearms,

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they pat, push and compress
the dam to make it watertight.

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As the dam becomes leak-proof,
the water level rises upstream

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and the beaver crew continue
to bulldoze in new layers of material.

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The dam-builders are programmed to
react to the sound of trickling water.

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They rush to block any leaks.

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Working as a well-drilled team,

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a beaver gang can build
5 feet of dam each day.

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They won't stop until
the river is completely blocked.

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The largest beaver dam ever recorded
was nearly a mile long.

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Now builder turns surveyor...

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the foreman checks
the family's work for leaks.

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It's taken several months' hard labour
to construct a dam over 300 feet long

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and the resulting pond now
stretches more than a mile upstream

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Stage one of the beaver project is complete

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Downstream the earthmovers
are on to Stage two

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carving out a road for access to their site

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A transport system is the second stage
of the beaver blueprint too＃

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but on this site there's
no mechanical assistance.

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The beavers use their claws and
teeth to rip up mud and vegetation,

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and their paws to shovel it into place.

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In just a few days they can excavate
an entire network of channels,

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leading away from the main pond,
far into their forest estate.

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For safety reasons, beavers like
to travel in the water

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steering clear of predators like bears.

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So instead of going overland,
they take the water to the trees.

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The longest channel ever measured
ran for more than 1,300 feet

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＃the builder and surveyor is
also an expert hydro-engineer.

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By blocking parts of the network,

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the beaver can vary the water level
in order to flood new areas
and reach new trees.

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And getting to the trees is what
all this hard work was all about.

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Trees are the raw material for Stage 3

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每 building a home.

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Meanwhile the beaver hydro-engineer
becomes a lumberjack.

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Four sharp incisors,
powered by huge jaw muscles,

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can whittle through a cottonwood tree
in a matter of hours.

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The beavers need to keep their wits
about them while they work...

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They listen to each creak and groan,

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and to be on the safe side, often
leave wind power to finish off the job

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But inexperienced apprentices
don't always time it right＃

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squashed beavers are occasionally found.

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Waiting for the wind means beavers can
have 4 or 5 trees ready to go at any time

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each one perhaps 3 feet in diameter
and up to 100 feet tall.

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A beaver lumberjack may chop
more than 200 trees a year.

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As a lumberjack's axe
has a tough iron blade,

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so the outer enamel of
a beaver's teeth is reinforced.

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The soft inner surface
wears down more rapidly,

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creating a chisel-like tree-cutting edge.

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Chainsaws may become blunt,

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but beavers teeth, like those
of all rodents, are self-sharpening＃

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they grow back as fast as they wear down.

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The beaver's sense of smell is hundreds
of times more sensitive than ours...

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and they seem to use it to sniff out
the tastiest, most nutritious trees.

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The crew's hard work soon radically
transforms the landscape

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每 leaving a large gap in the forest.

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Good lumberjacks don't leave a mess.

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As soon as each tree falls, it's cleared away.

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And for the beaver gang, it's payday.

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They've flooded the forest
so now they can swim to the trees＃

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cut them down and reach the juicy leaves,
twigs and bark at the top.

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Time for the green machines to refuel.

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The beaver strips the bark, and eats
the best chips, up to 2 pounds a day.

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Special micro-organisms in its guts
digest this high-fibre food.

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Now the canal network comes into
its own＃ as a bustling highway.

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Branches are shipped from
every corner of the property

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每 it's a major logistical operation.

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The journey ends here 每

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at the beavers' winter storage depot,
in the middle of the pond.

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This larder must be filled
within the next few weeks.

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It's all paws to the pump

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now the beavers' rear motor
goes into overdrive.

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Another wide load is delivered to the depot,

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and stored in the deepest part of the pond,

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where cold water will keep the food fresh.

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Each branch is pushed
right down into the mud.

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The larder contains rations
for the fast-approaching winter months

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Winter is a crucial deadline 每

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one the beaver builders
can't afford to overrun.

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As dusk falls, down the valley
the contractors take off for the weekend

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but the beaver crew don't miss a beat.

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On the night shift, beavers seem to
have an even greater sense of urgency

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unlike the neighbours.

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Productivity increases,

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and they often bundle up 5 or 6
branches in a single load.

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Not all the branches are stored in the larder

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some are diverted for a different purpose

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The beaver crew is ready
to construct the final stage and
crowning glory of their blueprint

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their equivalent of a log cabin
每 a 'lodge'.

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Over the past few months the family
have lived in temporary accommodation

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每 a hole in the riverbank.

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But now they build a timber framework house

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and render the outside with mud and sticks.

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Down the valley the man-made
log cabins are already underway...

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but will this team finish
before winter kicks in?

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A beavers' lodge can be more than
40 feet across and 10 feet high

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每 that's bigger than a double garage.

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Once the basic framework is in place,

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it's overlaid with yet
more vegetation and sticks.

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Each member of this crew
can turn their paw to anything.

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The plasterer arrives with mud to bind
the walls and insulate against the cold.

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Wattle and daub is a very effective technique.

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But how does the beaver crew know
when to start on the lodge?

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They take their cue
from the rising water levels

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once the pond reaches a certain depth
they automatically switch energies

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from dam construction to building a home.

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More and more logs are ferried in

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Before they use the logs,
the beavers strip the bark and eat it

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每 nothing goes to waste.

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All this manual labour helps
to keeps these builders super fit

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每 a beaver can lift
its own bodyweight in timber.

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From start to finish, it takes
just 20 days to build the lodge,

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using around 3 tonnes of raw materials.

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The beavers' home is high-security

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- protected by a moat, with several
concealed underwater entrances.

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Inside, the beavers carve
out individual chambers

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每 this is where they have their young.

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Beavers give birth in spring,
to 3 or 4 babies or kits,

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each one about the size of a guinea pig.

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The lodge is made up of 3 rooms,
each with a private entrance to the pond.

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The nursery, and then the sleeping quarters

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This one is taken by a pair of muskrats
每 they're permanent squatters!

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The third room is the beaver
family's feeding chamber.

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With last year's young still
at home, it's a full house.

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All these beaver bodies create
a kind of central heating.

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The humidity and warmth does, however,

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mean that fungi grow like
rising damp under the reed carpet.

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With front and back door access underwater

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the inhabitants can come and
go hidden from prying eyes.

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As well as being a cosy family home,

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this is now a prime piece
of detached waterfront property

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每 complete with landscaped garden.

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Lodge, larder, pond and channels
are all finished.

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The beavers are on schedule.

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Their deadline is in sight and
the building is almost complete.

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Down the valley the other team
is lagging behind＃

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00:18:06,700 --> 00:18:09,250
But they do have one big advantage

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每 their project has planning permission.

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Busy beavers can cause problems.

189
00:18:16,400 --> 00:18:18,350
In the past and still today,

190
00:18:18,400 --> 00:18:23,050
the beavers' fixation with building
has led them to butt heads with man.

191
00:18:29,300 --> 00:18:34,250
Flooding agricultural land
has put beavers on the most wanted list

192
00:18:35,600 --> 00:18:41,450
Farmers regularly clear small dams, but
larger ones require more drastic measures

193
00:18:56,100 --> 00:19:00,350
Months of hard work
are often blown sky high.

194
00:19:06,400 --> 00:19:11,850
But these resilient rodents have proved
more than a match for the dam busters.

195
00:19:14,400 --> 00:19:19,350
They quickly move in again to repair,
renovate and re-flood the fields.

196
00:19:23,000 --> 00:19:25,250
This persistence can be fatal.

197
00:19:25,300 --> 00:19:28,399
Because they return to fix a leaking dam,

198
00:19:28,400 --> 00:19:31,650
the beavers can easily swim right into a trap.

199
00:19:38,400 --> 00:19:43,950
But in recent years, the beavers'
building skill has been more appreciated

200
00:19:43,951 --> 00:19:47,550
Beavers are now moved from sites
where they're not wanted

201
00:19:47,551 --> 00:19:51,150
and released into new areas
as wildlife and wetland managers.

202
00:19:55,300 --> 00:19:58,850
Beavers create much more than
just a family home.

203
00:20:00,300 --> 00:20:04,350
The beaver pond also serves as
a firebreak during forest fires

204
00:20:04,400 --> 00:20:06,650
and a run-off when the river floods.

205
00:20:06,700 --> 00:20:09,950
It's a fishing lake and recreation area too.

206
00:20:10,500 --> 00:20:13,650
In the right place the beaver is a model tenant

207
00:20:13,700 --> 00:20:17,150
and free handyman, a true eco-engineer,

208
00:20:17,200 --> 00:20:22,050
producing a mosaic of habitats that
are suitable for many other species.

209
00:20:40,300 --> 00:20:43,899
Man and beaver are sharing their waterways

210
00:20:43,900 --> 00:20:47,950
but in the battle of construction,
who's the winner?

211
00:20:52,800 --> 00:20:57,350
Down the valley, snow has stopped
the contractors in their tracks.

212
00:20:58,100 --> 00:21:00,550
They've missed their deadline...

213
00:21:01,800 --> 00:21:05,550
This lodge will now lie empty until spring.

214
00:21:07,900 --> 00:21:11,250
The well-coordinated beaver team,
on the other hand,

215
00:21:11,300 --> 00:21:13,950
have hit nature's tight deadline.

216
00:21:20,500 --> 00:21:22,150
As the temperature drops,

217
00:21:22,200 --> 00:21:26,250
the true value of their painstaking
preparations becomes clear.

218
00:21:26,300 --> 00:21:29,350
Thanks to their hydro-engineering know-how

219
00:21:29,400 --> 00:21:32,750
the family is ready for the winter freeze

220
00:21:33,900 --> 00:21:36,350
This is the true test.

221
00:21:36,700 --> 00:21:40,750
If they hadn't dug their pond just
deep enough to stop it freezing solid,

222
00:21:40,800 --> 00:21:43,850
the lodge entrance
would have been icebound.

223
00:21:45,300 --> 00:21:50,450
And with the forest inaccessible,
the adjoining larder is a lifesaver.

224
00:21:50,500 --> 00:21:54,550
It means the beavers can nip out
for food throughout the colder months

225
00:21:54,600 --> 00:21:57,650
without having to venture far
into the woods

226
00:21:59,300 --> 00:22:03,350
The beaver builders have designed
the perfect winter refuge...

227
00:22:03,400 --> 00:22:08,950
safe and well-stocked with food 每
ideal for raising chips off the old block.

228
00:22:09,200 --> 00:22:13,750
It's a spacious home, where all
the family can sit out winter

229
00:22:13,800 --> 00:22:16,050
snug and warm.

230
00:22:20,100 --> 00:22:22,850
And if the central heating gets too high,

231
00:22:22,900 --> 00:22:27,550
the occupants can let off steam
through an extractor vent.

232
00:22:27,600 --> 00:22:32,350
So who, in this valley,
wins the title 'Master Builder'?

233
00:22:32,600 --> 00:22:35,650
No contest 每 it's the beaver.

234
00:22:36,300 --> 00:23:04,850
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