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Last time, we brought you winter.
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[HOWLING]
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Wildlife struggled
in freezing temperatures.
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[BEAR GROWLING]
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00:00:09,240 --> 00:00:11,840
Now, spring is here.
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Life is about to change,
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but not always for the better.
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The thaw will melt the snow
in the mountains
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and cause over one million tons
of melt water
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to crash through Yellowstone.
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Only the strongest animals will survive.
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Welcome to
Yellowstone, The Toughest Spring.
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[BIRD CHIRPING]
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It's the end of April
and seven degrees Celsius.
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The thaw is well underway.
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Spring has come to Yellowstone.
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Mammals big and small
are emerging from their dens,
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birds are courting and nesting,
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the days are getting longer and warmer.
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Now, you may think
that life is going to get easier.
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Yellowstone is bursting into life.
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[HUMMINGBIRD BUZZING]
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Humming birds return after
spending their winter in the warm south.
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Moose feast on the first green shoots.
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[SINGING]
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Bison migrate
back to their calving grounds.
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We're in the north-west of the USA,
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2,000 metres high up in the Rockies.
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Known as the
Greater Yellowstone Ecosystem,
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it's an area the size of Scotland,
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includes two national parks,
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and is bounded on three sides
by mountain ranges.
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Biologist Patrick Aryee
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is at the southern end
of Greater Yellowstone,
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catching up with one species that faces
its greatest challenge in spring.
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Behind me are the Teton mountains,
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and this is the Snake River,
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home to North America's
largest rodent, the beaver.
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There are 15 of them
living on this stretch of river,
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and they've built this enormous dam.
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I can't believe that this dam
is not a man-made structure,
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and that it's been made by beavers.
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I mean, it's...incredible!
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Look at the size of these branches,
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and even, here we go,
these huge rocks as well.
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It acts as a way to slow down
the waterways,
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like speed bumps almost.
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But I gotta say that they are nature's
most incredible engineers.
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But at this time of year,
their dam is in real danger.
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Soon enough, all that snow is gonna melt
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and all that melt water
is gonna start flowing down
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into these river systems.
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And as that water starts to flow
and cascade along this river,
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it could damage and even destroy
not only the dam,
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but also the lodge.
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And the lodge is where the beavers
have been holed up
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for the last five months.
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Now, we've got a camera rig set up,
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so we can actually see
exactly what's going on inside there
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right now.
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If I come over here...
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That is incredible.
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Oh, they're just starting to wake up.
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[GROANS]
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In this lodge we've got...
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There's two yearlings in there,
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two two-year-olds, and then, one adult.
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There should be another one,
but I can't see it.
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This is our beaver family,
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and we're gonna be
getting to know them very well.
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[MOANING]
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And we'll be following them
over the coming months
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to see how they cope
when the spring floods hit.
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Just seen one dive.
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Beavers are most comfortable in water.
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Their lumbering bodies
are quite ungainly on land.
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He's huge!
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This stretch of river
is home to 15 beavers.
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00:05:02,200 --> 00:05:06,840
In April, the riverbank is usually
covered in a blanket of snow,
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00:05:06,920 --> 00:05:09,280
so the beavers
stay snuggled in their den.
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00:05:10,440 --> 00:05:13,880
But this year,
the snow has already disappeared.
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According to scientists,
the thaw is three weeks early.
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That means the beavers
can start venturing out
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on the search for new green shoots.
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This is brilliant.
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I'm just following this beaver,
and hopefully,
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I'll get to see him
when he comes up onto this next dam.
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This beaver hasn't eaten fresh food
for five months.
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Over winter, the beaver's food supply
is locked in snow and ice.
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They feed on twigs, leaves and bark
of aspen and willow trees.
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But when there's so much snow
on the ground,
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they can't get to it.
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Yet beavers don't hibernate,
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so must keep eating
throughout the winter to survive.
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Their solution is ingenious.
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00:06:12,520 --> 00:06:15,320
They collect a mound of twigs
and vegetation
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big enough to last for five months
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00:06:17,840 --> 00:06:20,840
and store it by the underwater
entrance to their home.
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00:06:21,520 --> 00:06:23,720
Even when the river freezes over,
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they have a larder
just a moment's swim away.
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00:06:30,760 --> 00:06:32,440
But by the end of winter,
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the rotten twigs
have lost most of their protein.
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This beaver is surviving
on his own body fat.
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00:06:41,680 --> 00:06:44,880
The early thaw, however,
has given him a lifeline.
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This year, he can forage for fresh food
three weeks earlier than normal.
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It's just what his hungry family needs.
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00:07:01,200 --> 00:07:03,920
Okay, that adult is now
back inside the lodge...
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00:07:04,000 --> 00:07:05,400
[BEAVER PUPS YELPING]
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And it's got a mouthful of vegetation.
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[BEAVER PUPS YELPING]
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These beavers have lost a third
of their body weight over winter.
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To gain that weight back,
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they'll need to eat
a kilogram of twigs and leaves
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every single day.
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The younger beavers squeak
to demand food,
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but when competition is this fierce
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it's every beaver for itself.
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[AGGRESSIVE SQUEAKING]
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In spring,
twigs are rich in sugars and proteins,
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just what they need
to kick start their recovery.
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But to reach the fresh food,
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the beavers must first get to work.
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Not only are beavers
phenomenal engineers
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building all those dams,
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but they're also
professional lumberjacks
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and they can take down whole trees,
just like this one,
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and they do that
using their super sharp teeth.
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These bottom teeth are just like chisels
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and what they'll do is,
get their head in sideways
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and chew away at the bark.
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00:08:19,400 --> 00:08:21,640
With smaller trees,
they'll go right the way through
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and you'll often see beavers
running away
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just before the trees fall down,
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but with big ones like this one,
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they'll only get so far
and then they'll move away
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and let the wind do the rest of the job
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[CREAKING AND CRACKING]
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[THUDS]
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Now, this is a really big tree,
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00:08:38,720 --> 00:08:41,320
but the part the beavers
are really interested in
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is up here, the top third,
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and I see where they've gnawed away
at this end
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and hauled all the branches
back to the river
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to construct their lodge and the dams.
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And making sure
their dams are re-enforced
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before the spring floods hit is crucial.
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There are five dams
on this stretch of river.
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This entire waterway, this system,
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00:09:06,720 --> 00:09:09,640
has been created by these beavers.
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00:09:09,720 --> 00:09:14,280
They've made these series of dams
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which kind of create this lock system.
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The beavers have turned
what was a small stream
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into a series of deep ponds.
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These pools allow them
to stay in the water while foraging.
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On land, they're easy prey
for predators like wolves and bears,
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but crucially, this dam system
also slows down the flood water.
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At two metres wide and 40 metres long,
the main dam is the strongest.
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But if this one breaches,
the others will go too.
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[YELPING]
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Right now,
the beavers are safe in their lodge,
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but I'll follow them closely
and find out how they get on
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as spring takes hold.
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HUMBLE: For many animals,
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spring is the most important
time of year.
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It's now May.
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[SINGING]
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As soon as the snow melts,
fresh vegetation appears.
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[STREAM GUSHING]
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Scientists call it
the "spring green-up,"
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00:10:32,160 --> 00:10:35,400
and it drives all life in Yellowstone.
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One animal relies on it
more than almost any other,
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the Rocky Mountain elk.
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There are over 20,000 elk
in Yellowstone.
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As the green-up moves from the lowlands
to high mountain pastures,
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the elk move with it.
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This magnificent herd of elk
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that is straddling
right across the sagebrush here
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and up the hill,
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are on their way to the calving grounds
a little bit further north from here.
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00:11:07,960 --> 00:11:10,360
They'll be giving birth
over the next few weeks.
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They'll hide their youngsters
in the undergrowth,
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while they go off to feed.
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This is a crucial move
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in order to protect them from predation
by the largest carnivore here,
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the grizzly bear.
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Now, there are some grizzlies
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that have become particularly adept
at finding those youngsters,
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and that source of protein
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is really great for adult bears
and their cubs
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needing desperately to put on weight
after a long winter hibernation.
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It's as the snowline retreats
from the valleys to the foothills,
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that the female grizzlies
and their cubs start emerging.
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They usually stay close to their dens
until the end of May,
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but this year, the warm weather
has enticed the bears away
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earlier than usual.
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But the elk calves
won't be born for another month.
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00:12:17,080 --> 00:12:20,800
So life for these cubs
will now be harder.
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00:12:20,880 --> 00:12:25,160
They will have to scratch a living
digging up roots and grasses.
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Grizzly expert Casey Anderson,
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00:12:32,880 --> 00:12:36,880
is already seeing signs
that there are plenty of bears around.
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00:12:38,400 --> 00:12:41,640
They've been using trees
as scratching posts.
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00:12:42,760 --> 00:12:44,600
ANDERSON: Yeah, this thing's been
getting hammered.
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00:12:44,720 --> 00:12:47,000
Look at all this.
They're leaving their scent behind,
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00:12:47,880 --> 00:12:51,080
'cause there's just all kinds of mud
and hair stuck on here, so...
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00:12:51,680 --> 00:12:54,840
Yeah, it's going to be cool to see
who is back in town.
206
00:12:56,280 --> 00:12:59,880
HUMBLE: Patrick is joining Casey
in the Gallatin Mountains
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00:12:59,960 --> 00:13:03,800
to find out whether the early bears
are getting enough to eat.
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00:13:06,480 --> 00:13:09,360
ARYEE: Casey's tracked a mother
and her two-year-old cubs
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00:13:09,480 --> 00:13:12,160
to a wooded area
halfway down the mountain.
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00:13:12,840 --> 00:13:17,640
They've been feeding all morning
and are likely to be somewhere close by.
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00:13:18,400 --> 00:13:22,040
[SOFTLY] From here on, we gotta go slow,
even lower our voice.
212
00:13:23,040 --> 00:13:24,480
The wind's really goin'
in the wrong direction.
213
00:13:25,440 --> 00:13:29,200
Wind's carryin' our scent right towards
where the grizzly bears are
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00:13:29,280 --> 00:13:31,360
and they have a sense of smell
that's about seven times stronger
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00:13:31,440 --> 00:13:33,160
-than a bloodhound.
-All right.
216
00:13:33,240 --> 00:13:36,160
ARYEE: Casey thinks the bears
will stay in this area for a while
217
00:13:36,240 --> 00:13:39,040
to make the most
of the early green shoots.
218
00:13:39,120 --> 00:13:41,760
So for us, it's a waiting game.
219
00:13:43,760 --> 00:13:45,640
ANDERSON: It's amazing
'cause they just come out of nowhere.
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00:13:45,720 --> 00:13:47,960
In that deep sagebrush,
they love to just get down
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00:13:48,040 --> 00:13:49,440
out of this wind
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00:13:49,520 --> 00:13:51,440
and lay there flat to the ground,
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00:13:51,520 --> 00:13:52,800
cuddle up, keep each other warm.
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So we just gotta keep scanning.
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00:13:55,640 --> 00:14:00,080
You'll see, like, a little ear,
or they'll stretch their little paw up.
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00:14:00,200 --> 00:14:02,440
You gotta look for those
little subtle things popping out.
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00:14:04,360 --> 00:14:07,360
ARYEE: What makes you think
that this is a good spot for bears?
228
00:14:07,720 --> 00:14:11,400
You look right down here
in this green patch,
229
00:14:11,560 --> 00:14:15,800
you'll see where the bears
have been excavating there,
230
00:14:15,880 --> 00:14:17,600
and that's just classic
in the spring time.
231
00:14:17,680 --> 00:14:20,880
They'll find these, first,
really green spots,
232
00:14:20,960 --> 00:14:23,040
that get a lot of moisture,
get a lot of sun.
233
00:14:23,120 --> 00:14:27,280
So there's been a lot of activity
down in that meadow there, so,
234
00:14:27,360 --> 00:14:29,120
it's a really good chance
235
00:14:29,200 --> 00:14:31,200
that whoever did that,
whatever bears did that,
236
00:14:31,280 --> 00:14:33,640
are gonna come back to that spot
and do it again.
237
00:14:36,040 --> 00:14:39,240
ARYEE: But plants contain
less than half the protein of meat,
238
00:14:41,080 --> 00:14:44,680
so they'll have to eat huge amounts
to keep up their calorie count.
239
00:14:53,320 --> 00:14:54,640
[WHISTLES AND WHISPERS]
Right there! Right there!
240
00:14:54,880 --> 00:14:55,880
Where?
241
00:14:59,840 --> 00:15:00,960
Right here, right here.
242
00:15:01,040 --> 00:15:02,320
Right down in the trees.
243
00:15:04,160 --> 00:15:05,920
ARYEE: Oh, yeah, yeah,
yeah, yeah, yeah, yeah.
244
00:15:06,360 --> 00:15:07,600
Three bears!
245
00:15:07,720 --> 00:15:09,200
[EXCITED LAUGH]
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00:15:10,160 --> 00:15:11,240
ARYEE: One,
247
00:15:11,720 --> 00:15:13,000
two,
248
00:15:14,040 --> 00:15:15,640
three, looks like...
249
00:15:15,720 --> 00:15:20,200
Looks like a big female,
one light cub, one dark cub.
250
00:15:21,520 --> 00:15:23,600
-It's pretty awesome!
-Yeah.
251
00:15:26,240 --> 00:15:28,680
ANDERSON: Those look like
two-year-old cubs.
252
00:15:29,360 --> 00:15:31,960
You know, this area is...
Just draws in females with cubs.
253
00:15:32,640 --> 00:15:36,360
At a spot like that, well, you know,
you get dandelions, grasses and sedge,
254
00:15:36,440 --> 00:15:38,760
even biscuit root
will grow in that area,
255
00:15:38,840 --> 00:15:43,040
and that's all on the menu for
a grizzly bear this time of year, so,
256
00:15:43,120 --> 00:15:44,880
they come right to that spot
and they'll keep coming back
257
00:15:44,960 --> 00:15:47,240
over and over and over again,
till everything is gone.
258
00:15:47,320 --> 00:15:51,960
So basically, this area here is kind of
like an all-you-can-eat veggie buffet.
259
00:15:52,040 --> 00:15:53,520
Yeah, it's a salad bar.
260
00:15:55,040 --> 00:15:58,840
ARYEE: A dandelion plant
contains only about three calories,
261
00:15:58,920 --> 00:16:00,960
and grass, even less.
262
00:16:02,080 --> 00:16:05,000
The early thaw is at least helping.
263
00:16:05,080 --> 00:16:10,080
But they must find two fields every day
with rich sources of food like this one
264
00:16:10,160 --> 00:16:12,360
if they're going to survive.
265
00:16:20,360 --> 00:16:22,000
HUMBLE: It's not just grizzly bears
266
00:16:22,080 --> 00:16:24,840
that must exploit
the best pockets of food.
267
00:16:27,560 --> 00:16:30,440
The Rocky Mountain elk
are still moving north,
268
00:16:30,520 --> 00:16:32,040
following the green-up.
269
00:16:36,480 --> 00:16:39,680
And another of Yellowstone's residents
is ahead of them,
270
00:16:40,360 --> 00:16:41,600
the bison.
271
00:16:42,480 --> 00:16:45,920
This year, the bison and elk are lucky.
272
00:16:46,000 --> 00:16:48,680
Not only have they had a milder winter,
273
00:16:48,760 --> 00:16:52,400
but the early thaw
means there's plenty of grass around,
274
00:16:54,920 --> 00:16:58,120
and now in spring, it's full of protein.
275
00:17:02,040 --> 00:17:05,040
I've come to the northern range
of Yellowstone.
276
00:17:06,120 --> 00:17:09,840
Park biologists have reported
that a large herd of bison
277
00:17:09,920 --> 00:17:11,480
has come here to feast,
278
00:17:11,560 --> 00:17:14,640
because this year,
the snow has already melted.
279
00:17:15,920 --> 00:17:18,760
The park is home to about 5,000 bison.
280
00:17:19,880 --> 00:17:20,920
[GRUNTING]
281
00:17:21,000 --> 00:17:24,840
This herd has made it through to spring
fit and strong,
282
00:17:24,920 --> 00:17:28,840
which is crucial for the survival
of their new-born calves.
283
00:17:30,240 --> 00:17:35,440
Calving season is just beginning here
in Yellowstone National Park.
284
00:17:35,520 --> 00:17:39,200
This is the very first one I've seen.
It's suckling I think.
285
00:17:41,400 --> 00:17:44,400
A quarter of the baby bison
in Yellowstone
286
00:17:44,480 --> 00:17:47,280
die in their first two months,
287
00:17:47,360 --> 00:17:51,720
but this mild weather will give them
a much greater chance of survival.
288
00:17:52,560 --> 00:17:54,040
There's a tiny one,
289
00:17:54,640 --> 00:17:57,320
looks like it's probably
only a day or two old.
290
00:17:58,680 --> 00:18:02,160
Beautiful, you can see that lovely
chestnutty colour.
291
00:18:02,680 --> 00:18:04,440
They're extraordinary, bison calves.
292
00:18:04,520 --> 00:18:07,600
Within half an hour of being born,
they're up on their feet
293
00:18:07,680 --> 00:18:09,280
and within an hour or two,
294
00:18:09,360 --> 00:18:11,680
they can run to keep up
with their mothers.
295
00:18:16,640 --> 00:18:19,520
Sticking close
to their mothers is vital,
296
00:18:24,680 --> 00:18:25,880
because this spring,
297
00:18:25,960 --> 00:18:29,600
Yellowstone's top predator
is particularly hungry.
298
00:18:29,680 --> 00:18:30,840
[WOLF HOWLING]
299
00:18:31,480 --> 00:18:35,000
There are 100 wolves
in Yellowstone National Park.
300
00:18:36,680 --> 00:18:40,560
They rely on bison and elk
to survive the winter.
301
00:18:42,840 --> 00:18:45,880
But whilst the mild winter
has been good for the bison,
302
00:18:45,960 --> 00:18:47,880
it's been bad for the wolves.
303
00:18:48,280 --> 00:18:50,040
They've struggled to hunt.
304
00:18:52,280 --> 00:18:57,600
Back in the winter, biologist Doug Smith
observed the problem first-hand.
305
00:18:58,400 --> 00:19:02,440
Doug and his team
monitor these wolves every single day.
306
00:19:03,480 --> 00:19:07,200
They've noted that whilst mild winters
help the prey,
307
00:19:07,280 --> 00:19:10,080
they put predators at a disadvantage.
308
00:19:11,600 --> 00:19:15,560
When you're in ankle-deep snow
or just elbow-deep snow,
309
00:19:15,640 --> 00:19:20,560
a healthy elk, bison, deer
will always outrun a healthy wolf.
310
00:19:21,360 --> 00:19:24,400
HUMBLE: Wolves and elk
run at the same speed,
311
00:19:24,880 --> 00:19:27,160
but elk are built for endurance.
312
00:19:27,240 --> 00:19:30,720
With sure footing,
they can keep going for longer.
313
00:19:31,160 --> 00:19:34,880
So this winter,
the wolves have been going hungry.
314
00:19:37,560 --> 00:19:41,440
They're having a particularly tough time
here in the northern range,
315
00:19:41,520 --> 00:19:45,360
where five packs
compete for food and territory.
316
00:19:48,200 --> 00:19:51,440
Doug has studied these wolves
for over 20 years
317
00:19:51,680 --> 00:19:55,640
and in the last decade,
their numbers have fallen dramatically.
318
00:19:58,600 --> 00:20:03,400
One pack known by park biologists
as the Lamar Canyon Pack
319
00:20:03,480 --> 00:20:05,320
is extremely weak.
320
00:20:06,120 --> 00:20:08,200
If they don't gain strength quickly,
321
00:20:08,320 --> 00:20:11,640
they risk losing their territory
to other wolves.
322
00:20:13,920 --> 00:20:18,160
Our wildlife camera team is down
in the Lamar valley, following them.
323
00:20:21,920 --> 00:20:25,440
From a mile off,
they spot some unusual behaviour.
324
00:20:28,720 --> 00:20:32,320
The wolves are taking on
a whole herd of bison.
325
00:20:34,920 --> 00:20:37,720
They're hoping to snatch
a new-born calf.
326
00:20:38,720 --> 00:20:41,640
This is a sign
that the pack is desperate.
327
00:20:44,160 --> 00:20:47,320
Doug is helping us
to analyse what's going on.
328
00:20:49,880 --> 00:20:53,760
SMITH: These bison
are doing classic defence.
329
00:20:54,920 --> 00:20:56,120
They group together, they're big.
330
00:20:56,200 --> 00:20:59,320
They're not moving
other than to attack the wolves.
331
00:21:01,680 --> 00:21:06,400
HUMBLE: This is an age-old dance
between power and agility.
332
00:21:07,640 --> 00:21:11,520
Wolves may be quick,
but bison are strong.
333
00:21:13,080 --> 00:21:16,920
Getting this close
risks a kick to the skull.
334
00:21:20,320 --> 00:21:24,520
SMITH: Wolves would like to spread
this group apart, break it up
335
00:21:24,600 --> 00:21:26,440
and then that would free up
one of these calves
336
00:21:26,520 --> 00:21:27,960
who they can grab.
337
00:21:32,920 --> 00:21:34,760
HUMBLE: A female charges,
338
00:21:34,840 --> 00:21:37,520
threatening to lash them
with her hooves.
339
00:21:37,600 --> 00:21:40,800
SMITH: You get caught by a foot,
you get caught by a horn,
340
00:21:40,880 --> 00:21:42,480
injury, death.
341
00:21:48,240 --> 00:21:50,600
It's fascinating footage to watch.
342
00:21:50,720 --> 00:21:53,640
They're being aggressive,
yet very careful.
343
00:21:54,400 --> 00:21:59,520
Wolves definitely feel safer
pursuing a fleeing prey,
344
00:21:59,600 --> 00:22:04,080
'cause they can kinda come in
from behind, grab and pull down.
345
00:22:04,160 --> 00:22:08,120
HUMBLE: To attack a standing herd
means these wolves are desperate.
346
00:22:09,920 --> 00:22:12,920
SMITH: As they get hungry
and it goes more days without food,
347
00:22:13,000 --> 00:22:14,720
they're gonna take more risks.
348
00:22:15,520 --> 00:22:17,400
HUMBLE: They finally close in.
349
00:22:17,480 --> 00:22:20,720
This is the break in the herd
they've been hoping for.
350
00:22:28,360 --> 00:22:29,920
[BISON GRUNTING]
351
00:22:30,000 --> 00:22:31,320
[WOLVES YELPING]
352
00:22:33,840 --> 00:22:36,080
SMITH: The mother
can't do all this by herself,
353
00:22:36,160 --> 00:22:37,560
the wolves outnumber her.
354
00:22:39,200 --> 00:22:40,240
They may get this calf.
355
00:22:40,320 --> 00:22:42,960
I can't believe this,
you rarely see this.
356
00:22:43,040 --> 00:22:44,240
[BISON GRUNTING]
357
00:22:52,800 --> 00:22:55,960
HUMBLE: But the calf makes it back
to the safety of the herd,
358
00:22:57,720 --> 00:23:00,440
leaving nine very hungry wolves.
359
00:23:02,800 --> 00:23:05,640
The Lamar Canyon pack has failed.
360
00:23:11,800 --> 00:23:15,880
Doug is concerned that these
warmer winters and early springs,
361
00:23:15,960 --> 00:23:19,080
are part of a worrying trend.
362
00:23:19,160 --> 00:23:22,680
We can see climate change
affecting the park now.
363
00:23:22,760 --> 00:23:26,520
Our wolf research has only been going
a little over 20 years,
364
00:23:26,600 --> 00:23:31,000
but you talk to people who were
in Yellowstone 40 or 50 years ago
365
00:23:31,080 --> 00:23:34,800
and winter severity is,
is just not like it used to be,
366
00:23:34,880 --> 00:23:38,280
and this is a big factor
in how this system works.
367
00:23:39,960 --> 00:23:41,720
This winter and last winter
368
00:23:41,800 --> 00:23:44,440
were two of our shortest winters
we've had.
369
00:23:44,520 --> 00:23:47,840
This, in a way, in a big-picture way,
favours the bison.
370
00:23:47,920 --> 00:23:51,480
So we lost our snow
at low elevation very early this year,
371
00:23:51,600 --> 00:23:55,080
and so any time the snow goes away,
it gives the bison better footing.
372
00:23:55,160 --> 00:23:57,480
They can deal with the wolves,
and secondly,
373
00:23:57,560 --> 00:24:00,120
it exposes the vegetation to sunlight,
374
00:24:00,200 --> 00:24:02,760
the condition of bison
will start to improve earlier,
375
00:24:02,880 --> 00:24:04,960
uh, and so that hurts
the wolves a little bit.
376
00:24:07,840 --> 00:24:09,760
And so, sitting aside
and watching life evolve
377
00:24:09,840 --> 00:24:11,560
with that going on
378
00:24:11,640 --> 00:24:13,440
uh, has got me scared stiff.
379
00:24:15,960 --> 00:24:17,920
HUMBLE: It's the rate of climate change
380
00:24:18,000 --> 00:24:21,120
that Doug and his fellow scientists
find so shocking.
381
00:24:22,280 --> 00:24:24,680
Temperatures here have been rising fast,
382
00:24:26,440 --> 00:24:30,520
and the last decade has been the warmest
since records began.
383
00:24:34,480 --> 00:24:37,080
With Yellowstone's winters
becoming shorter,
384
00:24:37,160 --> 00:24:39,600
and the spring starting earlier,
385
00:24:39,680 --> 00:24:43,160
one animal in particular
is extremely vulnerable,
386
00:24:49,880 --> 00:24:51,560
the great grey owl.
387
00:24:55,720 --> 00:25:00,040
These owls live
in some of the coldest forests on Earth,
388
00:25:00,120 --> 00:25:02,560
from Siberia to Scandinavia.
389
00:25:02,640 --> 00:25:07,120
Yellowstone is just about cold enough
for the owls to survive.
390
00:25:07,200 --> 00:25:09,000
But if it gets any warmer,
391
00:25:09,080 --> 00:25:12,440
scientists believe
they won't be able to hold on.
392
00:25:13,840 --> 00:25:18,320
Back in winter, cameraman Jeff Hogan
followed a pair of great grey owls
393
00:25:18,400 --> 00:25:20,160
in the Teton Mountains.
394
00:25:26,880 --> 00:25:31,160
Great grey owls rely on small rodents
like voles and gophers
395
00:25:31,240 --> 00:25:33,680
which live beneath the snow.
396
00:25:33,760 --> 00:25:37,080
But our biologists
believe that the changing climate
397
00:25:37,160 --> 00:25:38,840
is affecting their hunting.
398
00:25:39,280 --> 00:25:42,800
These owls
have to bust through this crust
399
00:25:42,880 --> 00:25:46,000
and then maybe another foot of snow
to get at their prey.
400
00:25:47,840 --> 00:25:51,120
HUMBLE: But erratic winter weather
caused the crust to melt,
401
00:25:51,200 --> 00:25:52,440
and then refreeze,
402
00:25:52,520 --> 00:25:55,520
making it impenetrable for the owls.
403
00:26:00,280 --> 00:26:05,480
And if they can't hunt,
great grey owls won't nest or lay eggs.
404
00:26:10,680 --> 00:26:11,960
ARYEE: Now it's spring,
405
00:26:12,040 --> 00:26:15,960
Jeff has been searching for owl chicks
in the Beartooth Mountains.
406
00:26:16,040 --> 00:26:19,320
The forest here is 300 years old,
407
00:26:19,400 --> 00:26:22,520
an ideal habitat for great grey owls.
408
00:26:27,200 --> 00:26:28,720
-There they are, three of 'em.
-Oh, wow!
409
00:26:30,080 --> 00:26:31,440
[OWL SHRIEKS]
410
00:26:34,960 --> 00:26:36,160
Oh, my goodness.
411
00:26:40,160 --> 00:26:42,200
The smaller one, she's been a runt.
412
00:26:42,440 --> 00:26:44,360
ARYEE: Despite the difficulties
of winter,
413
00:26:44,440 --> 00:26:46,920
we found a nest with three chicks.
414
00:26:47,000 --> 00:26:48,920
This is extremely unusual.
415
00:26:50,160 --> 00:26:53,800
When food is scarce, the smallest chick
can be eaten by its siblings,
416
00:26:53,880 --> 00:26:56,040
but this runt is still alive.
417
00:26:57,720 --> 00:26:59,560
How much of a success is it
418
00:26:59,640 --> 00:27:02,360
that we've got
three great grey owl chicks here?
419
00:27:03,000 --> 00:27:05,680
In these parts here,
this neck of the woods,
420
00:27:05,880 --> 00:27:09,960
it's about a 20% success rate
for the third chick.
421
00:27:10,040 --> 00:27:11,840
So most, you know,
422
00:27:11,920 --> 00:27:15,800
four out of five, perish by this...
By this time.
423
00:27:17,440 --> 00:27:19,280
So we've got some great parents here.
424
00:27:19,360 --> 00:27:22,520
Yeah. The reason is,
our winters have been quite mild,
425
00:27:22,600 --> 00:27:25,520
so the rodents, the prey,
has really benefited
426
00:27:25,600 --> 00:27:27,600
and their populations have really grown,
427
00:27:27,680 --> 00:27:29,560
which of course, then,
benefits the owls.
428
00:27:29,960 --> 00:27:31,720
And that could be making the difference
429
00:27:31,800 --> 00:27:33,960
on whether or not
the chick survives or not.
430
00:27:35,440 --> 00:27:39,520
ARYEE: The early thaw this year
has turned the owls' fortunes around.
431
00:27:39,600 --> 00:27:42,840
The milder weather
has led to a boom in rodent numbers.
432
00:27:46,360 --> 00:27:49,200
To reveal how
this has been helping the owls,
433
00:27:49,280 --> 00:27:52,880
Jeff has been searching
for their pellets.
434
00:27:54,840 --> 00:27:57,520
Yeah, I've got a pellet here
I collected this morning
435
00:27:57,600 --> 00:27:59,280
and look, you'll see the size of this.
436
00:27:59,360 --> 00:28:01,760
-[ARYEE LAUGHING]
-HOGAN: It's kinda disgusting.
437
00:28:02,280 --> 00:28:05,160
Okay, well, if I just break this apart
438
00:28:05,240 --> 00:28:07,600
why, you can see it is literally just...
439
00:28:09,640 --> 00:28:11,880
...hair and bone.
440
00:28:12,240 --> 00:28:13,240
HOGAN: Yeah.
441
00:28:14,240 --> 00:28:17,280
[GASPS] Look at that!
442
00:28:18,000 --> 00:28:20,760
That is an entire skull.
443
00:28:21,240 --> 00:28:22,320
Look at that,
you can even see the teeth.
444
00:28:22,400 --> 00:28:23,960
-HOGAN: Mmm-hmm.
-[GASPS] Here we go!
445
00:28:24,040 --> 00:28:25,040
Look, look, look, look!
446
00:28:25,160 --> 00:28:27,160
-HOGAN: There you go.
-Oh, that is brilliant.
447
00:28:27,240 --> 00:28:28,240
Yeah.
448
00:28:28,840 --> 00:28:30,680
ARYEE: A second skull,
449
00:28:30,760 --> 00:28:33,560
which means they would have had
two meals in quick succession.
450
00:28:34,720 --> 00:28:37,560
So far, the owls are doing well,
451
00:28:37,640 --> 00:28:40,760
but spring in Yellowstone
is unpredictable.
452
00:28:42,960 --> 00:28:46,680
After I leave,
the weather takes a turn for the worse.
453
00:28:46,760 --> 00:28:48,560
A storm blows in.
454
00:28:48,640 --> 00:28:50,920
It could mean death for the chicks.
455
00:28:51,560 --> 00:28:54,840
This rain makes... Makes it
a little more difficult for me
456
00:28:55,640 --> 00:28:57,120
to work in,
457
00:28:58,000 --> 00:29:01,640
but it makes it even more difficult
for the adult owls to hunt,
458
00:29:02,240 --> 00:29:05,960
being that it's just so noisy
and it masks any sounds
459
00:29:06,040 --> 00:29:07,440
that the rodents may be making.
460
00:29:07,960 --> 00:29:10,800
ARYEE: The runt is at the bottom
of the pecking order.
461
00:29:11,040 --> 00:29:14,960
As soon as food becomes scarce,
she'll be the first to lose out.
462
00:29:15,400 --> 00:29:19,080
If the weather doesn't change,
the runt may starve.
463
00:29:19,760 --> 00:29:21,200
[THUNDER CRASHING]
464
00:29:30,280 --> 00:29:34,240
HUMBLE: May is always the wettest month
of the year in Yellowstone,
465
00:29:34,320 --> 00:29:37,840
but this year,
it's far wetter than average.
466
00:29:40,800 --> 00:29:43,800
The reason can be found in the Pacific.
467
00:29:43,880 --> 00:29:48,080
The warming ocean
creates much more moisture in the air.
468
00:29:48,960 --> 00:29:52,560
This is channelled
directly up to Yellowstone,
469
00:29:52,640 --> 00:29:54,400
and when it hits the wall of mountains,
470
00:29:54,480 --> 00:29:57,760
the fury of the monsoon is unleashed.
471
00:29:58,080 --> 00:29:59,560
[THUNDER CRASHING]
472
00:30:04,240 --> 00:30:09,520
We experienced the most violent storm
that's been seen here for many years.
473
00:30:10,560 --> 00:30:13,360
Rain falling over three mountain ranges
474
00:30:13,480 --> 00:30:16,320
drains straight into
the Yellowstone basin.
475
00:30:16,680 --> 00:30:20,360
Overnight, water levels rise by a foot.
476
00:30:23,040 --> 00:30:25,720
For two weeks, rain pours down
477
00:30:25,800 --> 00:30:29,280
and thunderstorms reverberate
around the mountains.
478
00:30:30,560 --> 00:30:33,160
Then, at last, in early June,
479
00:30:35,520 --> 00:30:36,800
the weather breaks.
480
00:30:38,760 --> 00:30:41,720
But there's water everywhere.
481
00:30:42,640 --> 00:30:44,960
Melting snow, as well as rainwater,
482
00:30:45,400 --> 00:30:47,960
is now flowing into the river systems.
483
00:30:52,520 --> 00:30:55,560
Scientists have told me
to come to Yellowstone Falls
484
00:30:55,680 --> 00:30:57,600
to see the full effect.
485
00:31:19,000 --> 00:31:20,280
Back in March,
486
00:31:20,360 --> 00:31:22,360
Yellowstone Falls
was just a mere trickle
487
00:31:22,440 --> 00:31:26,640
and now, it's a dramatic torrent
of tumbling water.
488
00:31:31,040 --> 00:31:33,320
Every year, the thaw is different,
489
00:31:33,440 --> 00:31:35,680
and it's the rivers that hold the clues
490
00:31:35,760 --> 00:31:39,120
to tell us how this year's thaw
is progressing.
491
00:31:52,840 --> 00:31:56,160
Thousands of animals
rely on this river to survive.
492
00:31:57,880 --> 00:32:01,360
Greater Yellowstone
sits on the continental divide.
493
00:32:02,120 --> 00:32:05,080
This water flows west
to the Pacific ocean
494
00:32:05,160 --> 00:32:07,520
and east to the Atlantic.
495
00:32:08,400 --> 00:32:10,960
Without this huge reservoir of water,
496
00:32:11,040 --> 00:32:12,920
agriculture and industry,
497
00:32:13,000 --> 00:32:16,920
as well as wildlife
in the American west would die.
498
00:32:17,960 --> 00:32:22,320
So, understanding how much water
is draining into the river systems
499
00:32:22,400 --> 00:32:23,600
is vital.
500
00:32:24,360 --> 00:32:28,400
Teams of scientists have monitored
the stream flow in Yellowstone's rivers
501
00:32:28,480 --> 00:32:31,000
for the last 86 years.
502
00:32:31,080 --> 00:32:34,680
They've noticed that recently,
the pattern of the spring run-off
503
00:32:34,760 --> 00:32:36,160
has been changing.
504
00:32:37,520 --> 00:32:40,000
CHERYL MILLER: This piece of equipment
measures stream flow.
505
00:32:42,920 --> 00:32:44,480
HUMBLE: Hydrologist Cheryl Miller
506
00:32:44,560 --> 00:32:47,080
is keeping a close eye
on the rising water
507
00:32:47,160 --> 00:32:48,880
in the Yellowstone River.
508
00:32:49,280 --> 00:32:54,400
The data she gathers will reveal
how big the spring run-off will be.
509
00:32:55,760 --> 00:32:58,400
It's all done
with this little orange boat
510
00:32:58,480 --> 00:33:02,640
that uses sonar to measure
the depth and speed of the water.
511
00:33:02,720 --> 00:33:07,440
Combine those and you get the flow,
and that's the key figure.
512
00:33:08,680 --> 00:33:11,480
The rain has already raised
the water levels,
513
00:33:11,560 --> 00:33:15,760
but it's the thousands of tons of snow
still in the mountains
514
00:33:15,880 --> 00:33:18,400
that will make the real difference.
515
00:33:19,080 --> 00:33:21,120
-Okay, I've got her.
-MILLER: All right.
516
00:33:21,920 --> 00:33:25,720
So if you get a very sharp rise
in temperature,
517
00:33:25,800 --> 00:33:29,320
if that snow pack melts very quickly
and, you know, I've been in those...
518
00:33:29,400 --> 00:33:31,520
I've been in that snow pack,
the snow was above my head.
519
00:33:32,000 --> 00:33:35,560
Presumably,
if that does melt very quickly,
520
00:33:35,640 --> 00:33:40,040
the results downstream
must be, potentially, quite dramatic,
521
00:33:40,120 --> 00:33:41,680
quite destructive.
522
00:33:41,880 --> 00:33:46,160
Indeed. High-energy floods
can make great changes along a river.
523
00:33:46,240 --> 00:33:48,400
What's happening now is,
that the days are warm,
524
00:33:48,480 --> 00:33:50,720
but then, more importantly,
the nights are warmer
525
00:33:50,800 --> 00:33:53,480
and so, that snow pack
never refreezes at night.
526
00:33:53,600 --> 00:33:55,640
It continues to slowly melt
during the night
527
00:33:55,720 --> 00:33:58,240
and so that's what allows
the snow melt and the run-off
528
00:33:58,320 --> 00:34:00,120
-to accelerate during this time of year.
-Yeah.
529
00:34:01,680 --> 00:34:03,360
HUMBLE: Just looking at the river,
530
00:34:03,480 --> 00:34:05,880
does it appear that the flow
is faster now
531
00:34:05,960 --> 00:34:08,320
than it was
when you last collected data?
532
00:34:08,400 --> 00:34:11,400
It is. It's come up in the last
three or four days that it's...
533
00:34:11,480 --> 00:34:14,400
It may not be a lot faster,
but the volume is definitely bigger.
534
00:34:14,480 --> 00:34:16,880
There's more stream flow
than there was just a few days ago.
535
00:34:20,160 --> 00:34:22,280
HUMBLE: Cheryl's data reveals,
this year,
536
00:34:22,360 --> 00:34:24,760
the melting snow
is coming off the mountains
537
00:34:24,840 --> 00:34:26,800
more quickly than usual.
538
00:34:29,560 --> 00:34:34,080
The faster it runs off, the less water
is absorbed into the ground.
539
00:34:35,760 --> 00:34:40,320
These rapid spring melts
are more likely to cause flash floods.
540
00:34:41,200 --> 00:34:44,960
Patrick's finding out
how that's affecting the beavers.
541
00:34:51,680 --> 00:34:55,280
Here in the Snake River valley,
all the melt water from the Tetons
542
00:34:55,360 --> 00:34:57,280
is running down the mountains
543
00:34:57,360 --> 00:35:00,440
and it's headed
directly for our beaver dam.
544
00:35:02,000 --> 00:35:05,040
I'm meeting up with cameraman
Charlie Hamilton James.
545
00:35:05,920 --> 00:35:07,200
-Hey, Charlie.
-Hey, Patrick.
546
00:35:07,280 --> 00:35:08,400
ARYEE: How's it going, man?
547
00:35:08,480 --> 00:35:10,160
JAMES: Yeah, it's good.
Lovely weather, isn't it?
548
00:35:10,440 --> 00:35:12,720
ARYEE: He's spent the last week
watching the beavers
549
00:35:12,800 --> 00:35:14,800
struggle with the rising river.
550
00:35:18,960 --> 00:35:22,840
The water level is so much higher
551
00:35:22,920 --> 00:35:24,920
compared to last time I was here.
552
00:35:25,000 --> 00:35:27,360
Yeah, actually, really only
in the last few days,
553
00:35:27,440 --> 00:35:28,640
there was a lot of rain.
554
00:35:28,720 --> 00:35:30,520
All that water has resulted in this.
555
00:35:30,960 --> 00:35:32,040
JAMES: Yeah, I mean,
and what it's done
556
00:35:32,160 --> 00:35:34,520
-is actually starting to flood the dam.
-Mmm.
557
00:35:35,280 --> 00:35:38,680
ARYEE: In some places,
the dam has already breached.
558
00:35:39,960 --> 00:35:43,880
The beavers are working nonstop
to make sure all the leaks are plugged.
559
00:35:47,360 --> 00:35:49,840
They built this dam five years ago
560
00:35:49,920 --> 00:35:51,960
and every year, they fortify it.
561
00:35:53,640 --> 00:35:54,680
This one's been strengthened
562
00:35:54,760 --> 00:35:57,600
with a particularly
high number of stones.
563
00:35:59,960 --> 00:36:02,360
So what makes this spot prime habitat?
564
00:36:02,440 --> 00:36:05,400
Well, actually, weirdly,
beavers have made this spot.
565
00:36:05,480 --> 00:36:07,440
This actually started life as a stream
566
00:36:07,600 --> 00:36:10,880
and it's the beavers that came along
and stuck these dams in it
567
00:36:10,960 --> 00:36:15,400
and blocked its path
and created these long, slow ponds,
568
00:36:15,480 --> 00:36:16,920
and when you create a pond,
569
00:36:17,040 --> 00:36:18,960
you create another pond,
you create another...
570
00:36:19,040 --> 00:36:21,160
You create a wetland ecosystem.
571
00:36:21,240 --> 00:36:23,920
They're basically engineers,
but they're also gardeners.
572
00:36:24,320 --> 00:36:25,440
-I like that. "Gardeners."
-So they're creating
573
00:36:25,520 --> 00:36:28,000
this whole environment that suits them.
574
00:36:28,080 --> 00:36:30,440
But it's not just them
that benefit from this, right?
575
00:36:30,520 --> 00:36:32,320
-You've got amphibians, other mammals.
-Oh, absolutely.
576
00:36:32,400 --> 00:36:34,120
-Birds, that rely on this.
-Yeah, I mean,
577
00:36:34,200 --> 00:36:37,200
just sitting here now,
there's birds everywhere,
578
00:36:37,280 --> 00:36:38,360
there's swallows flying around,
579
00:36:38,480 --> 00:36:40,400
drinking and catching flies
off the surface.
580
00:36:40,840 --> 00:36:43,320
There's kingfishers eating fish.
There's lots of minnows here,
581
00:36:43,400 --> 00:36:45,240
lots of small fish,
perfect for kingfishers.
582
00:36:45,640 --> 00:36:48,560
Otters come through here,
ospreys, eagles.
583
00:36:48,720 --> 00:36:51,920
So, you know, they're ecosystem builders
is what they are, beavers,
584
00:36:52,000 --> 00:36:54,240
and more so,
really than any other animal.
585
00:36:57,280 --> 00:36:59,120
ARYEE: If the main dam is knocked out,
586
00:36:59,200 --> 00:37:01,800
it's not just the beavers
that will lose their home.
587
00:37:04,880 --> 00:37:07,320
The top is just about holding,
588
00:37:07,400 --> 00:37:12,080
but Charlie and I are heading underwater
to find out how solid the base is.
589
00:37:17,720 --> 00:37:19,320
[INDISTINCT CONVERSATION]
590
00:37:20,720 --> 00:37:24,040
JAMES: Just where my feet are now,
it actually starts here.
591
00:37:24,120 --> 00:37:26,160
The foundations are being laid here.
592
00:37:26,240 --> 00:37:28,240
And so, you know,
it's like ten-foot wide.
593
00:37:28,320 --> 00:37:31,080
You can't see it all,
'cause most of it is underwater.
594
00:37:31,760 --> 00:37:33,240
We got these dry suits on.
595
00:37:33,320 --> 00:37:36,640
Yeah, and really, in perfect,
in the spirit of full immersion,
596
00:37:37,560 --> 00:37:39,760
we should go in
and actually have a look.
597
00:37:39,840 --> 00:37:41,760
Is this where I find out
I've got the dud suit?
598
00:37:41,840 --> 00:37:43,200
JAMES: Yeah.
599
00:37:44,880 --> 00:37:46,120
[ARYEE CHUCKLES]
600
00:37:46,200 --> 00:37:48,760
JAMES: Actually, this is so much
better than I thought it would be.
601
00:37:48,840 --> 00:37:49,840
This is awesome.
602
00:37:50,160 --> 00:37:52,520
It's much clearer than I thought.
You can really see it.
603
00:37:54,640 --> 00:37:56,720
ARYEE: It's only when you get underwater
604
00:37:56,800 --> 00:38:00,000
that you see the skill
that's gone into building this dam.
605
00:38:03,240 --> 00:38:06,200
The beavers choose logs
up to two metres long
606
00:38:07,800 --> 00:38:12,080
and place them at an angle of 30 degrees
to hold back the water.
607
00:38:12,160 --> 00:38:14,760
This is precision engineering.
608
00:38:19,720 --> 00:38:20,920
JAMES: It's amazing, isn't it?
609
00:38:21,000 --> 00:38:22,960
It's so impressive. This is...
610
00:38:23,040 --> 00:38:25,120
You know, it's kind of a work of art.
611
00:38:27,880 --> 00:38:31,440
But the beaver's hard work
may not be enough.
612
00:38:31,520 --> 00:38:36,200
If the river rises any further,
the water could break through,
613
00:38:36,280 --> 00:38:39,560
and this watery world
might just disappear.
614
00:38:41,560 --> 00:38:42,760
[JAMES GRUNTING]
615
00:38:42,840 --> 00:38:44,160
JAMES: It's getting cold,
though, isn't it?
616
00:38:45,400 --> 00:38:46,720
[INDISTINCT CONVERSATION]
617
00:38:49,800 --> 00:38:54,680
HUMBLE: It's now mid-June,
and temperatures reach 28 degrees,
618
00:38:57,880 --> 00:39:01,520
seven degrees above average
for this time of year.
619
00:39:08,920 --> 00:39:12,480
The snow recedes
halfway up the mountains,
620
00:39:12,560 --> 00:39:16,880
revealing the highest feeding grounds
in Greater Yellowstone,
621
00:39:16,960 --> 00:39:19,520
and close behind are all the animals
622
00:39:19,600 --> 00:39:24,320
taking advantage of the final stage
of this year's spring green-up.
623
00:39:31,800 --> 00:39:34,120
At two and half thousand metres,
624
00:39:34,240 --> 00:39:38,760
this vast wilderness
provides food for thousands of animals.
625
00:39:40,960 --> 00:39:43,440
Elk that over-wintered
down in the valleys,
626
00:39:43,520 --> 00:39:46,720
finally arrive
back in these high pastures,
627
00:39:46,800 --> 00:39:48,600
where they'll raise their calves.
628
00:39:52,960 --> 00:39:55,200
These meadows are a feasting ground,
629
00:39:55,720 --> 00:39:58,040
full to the brim with wildlife...
630
00:39:58,520 --> 00:40:01,320
The hunters, as well as the hunted.
631
00:40:01,640 --> 00:40:03,000
[WOLF GROWLING]
632
00:40:09,840 --> 00:40:14,440
Opportunistic black bears
take advantage of a low bird's nest
633
00:40:14,520 --> 00:40:16,680
and defenceless chicks.
634
00:40:16,760 --> 00:40:20,640
At this time of year,
any food is fair game.
635
00:40:23,040 --> 00:40:26,720
ARYEE: The grizzly bears
are also joining the feeding frenzy.
636
00:40:27,440 --> 00:40:29,320
I'm catching up with Casey,
637
00:40:29,400 --> 00:40:33,200
who's following the fortunes
of one young bear family.
638
00:40:33,960 --> 00:40:37,280
These new-born cubs
are only four months old.
639
00:40:38,600 --> 00:40:40,320
With nowhere to hide from predators,
640
00:40:40,400 --> 00:40:44,160
this meadow is a dangerous place
for baby bears,
641
00:40:44,240 --> 00:40:46,360
but their mother has no choice.
642
00:40:48,680 --> 00:40:50,560
She's following the melting snow
643
00:40:50,640 --> 00:40:53,400
to make sure that she and her cubs
644
00:40:53,480 --> 00:40:56,240
get enough protein from the new growth.
645
00:40:58,880 --> 00:41:01,000
-[LAUGHS]
-Aw, they're so cute.
646
00:41:01,560 --> 00:41:03,800
-[LAUGHS]
-ARYEE: So small.
647
00:41:07,000 --> 00:41:08,200
So you know this bear?
648
00:41:08,280 --> 00:41:09,920
Yeah, you can count on her
like clockwork.
649
00:41:10,760 --> 00:41:15,840
Everything that a little cub
needs to learn to survive its lifetime,
650
00:41:15,920 --> 00:41:18,160
they're learning in these
first few years with its mother.
651
00:41:18,280 --> 00:41:20,000
Like, where to go,
what time of the year,
652
00:41:20,080 --> 00:41:22,640
how to dig the roots.
They're learning all that right now.
653
00:41:22,800 --> 00:41:23,920
This one here, you know,
654
00:41:24,000 --> 00:41:26,040
the year after year
that I've watched her,
655
00:41:26,120 --> 00:41:28,880
she usually keeps almost all
of her cubs. She's a great mother.
656
00:41:29,480 --> 00:41:32,520
ARYEE: In the ten years
that Casey's been following this female,
657
00:41:32,600 --> 00:41:36,840
he's also seen her teach her offspring
a more gruesome skill.
658
00:41:38,040 --> 00:41:40,040
She's a known predator.
659
00:41:40,120 --> 00:41:43,080
During this time of year,
she will actually go around
660
00:41:43,160 --> 00:41:45,200
looking for elk calves
that were just born
661
00:41:45,280 --> 00:41:46,840
that are stashed out here
in the sage brush,
662
00:41:46,920 --> 00:41:49,720
and these little cubs will be in tow,
and they'll be watching, so,
663
00:41:49,800 --> 00:41:51,040
it's a very learned behaviour.
664
00:41:51,120 --> 00:41:54,720
And some bears right in the same area
don't hunt elk calves at all
665
00:41:54,800 --> 00:41:55,880
'cause their mother didn't teach 'em.
666
00:41:55,960 --> 00:41:57,920
They didn't get the chance
to learn this.
667
00:41:58,000 --> 00:42:01,280
These little guys are gonna learn that
and I'll tell you, this time of year,
668
00:42:01,360 --> 00:42:04,160
that protein for these little bear cubs
is essential,
669
00:42:04,240 --> 00:42:06,880
and that may just be the thing
that gives them the advantage
670
00:42:06,960 --> 00:42:08,920
to be strong bears.
671
00:42:09,360 --> 00:42:12,120
ARYEE: But of all the survival skills
they'll need to learn,
672
00:42:12,200 --> 00:42:15,360
the most important
is how to spot danger.
673
00:42:17,480 --> 00:42:20,960
There we've got Mum in the middle
of this sagebrush,
674
00:42:21,040 --> 00:42:23,720
and these little cubs
bobbing their head up and down.
675
00:42:24,720 --> 00:42:28,600
Surely this is a dangerous time
for them as well?
676
00:42:28,680 --> 00:42:33,520
How difficult is it, you know,
to be a new-born grizzly bear cub?
677
00:42:34,120 --> 00:42:35,320
ANDERSON: Very difficult.
678
00:42:36,000 --> 00:42:39,040
Stats say about 50% of bear cubs
in their first year,
679
00:42:39,120 --> 00:42:40,120
they don't make it.
680
00:42:41,040 --> 00:42:44,080
And there are so many things out there
that are trying to kill them.
681
00:42:45,120 --> 00:42:46,520
A male grizzly's one of them.
682
00:42:46,600 --> 00:42:47,760
You know, a male grizzly
683
00:42:47,840 --> 00:42:50,520
knows that she won't mate
as long as she has cubs.
684
00:42:50,600 --> 00:42:52,280
He comes in there
and he can eliminate those cubs,
685
00:42:52,360 --> 00:42:54,560
then she will come into oestrous
and she will mate.
686
00:42:54,800 --> 00:42:59,040
So, big male bears,
big danger for these guys.
687
00:43:01,280 --> 00:43:04,600
ARYEE: Male grizzlies
are known to roam this area,
688
00:43:04,680 --> 00:43:07,240
so their mother must stay on high alert.
689
00:43:09,760 --> 00:43:12,160
And what's that scar on her head?
690
00:43:12,240 --> 00:43:14,000
It looks like she got some sort of scar.
691
00:43:14,120 --> 00:43:15,560
ANDERSON: Yeah, it's new for her,
692
00:43:15,640 --> 00:43:18,960
so I'm assuming,
now that she's got these little cubs,
693
00:43:19,040 --> 00:43:21,000
that scar's probably
from protecting them
694
00:43:21,080 --> 00:43:22,840
against a big male.
695
00:43:22,920 --> 00:43:27,160
And when it comes to their defence,
these females, they don't care.
696
00:43:27,240 --> 00:43:29,160
They're gonna go against
the biggest male grizzly,
697
00:43:29,240 --> 00:43:32,000
and it looks like
she probably protected her cubs,
698
00:43:32,080 --> 00:43:33,400
but came away with a pretty big scar.
699
00:43:36,240 --> 00:43:37,600
Oh, she's nursing right now.
700
00:43:38,240 --> 00:43:40,560
-She's laying all the way on her back.
-Oh, yeah.
701
00:43:40,760 --> 00:43:41,920
ANDERSON: Yeah,
they're gonna get in there,
702
00:43:42,000 --> 00:43:43,360
they're gonna relax.
703
00:43:43,440 --> 00:43:45,400
Nothing better for a little cub
than that right there,
704
00:43:45,480 --> 00:43:48,000
but Mom, she still has to pay attention,
705
00:43:48,080 --> 00:43:49,760
and you can see,
she'll just keep picking her head up
706
00:43:49,840 --> 00:43:51,680
and watching, looking for danger.
707
00:43:52,000 --> 00:43:53,320
There's a good chance
that these two little dudes
708
00:43:53,400 --> 00:43:54,840
will grow up to be adult bears,
709
00:43:55,800 --> 00:43:59,000
and she's a rock star mom for sure.
710
00:44:00,120 --> 00:44:04,560
ARYEE: Bears spend the heat of the day
bedded down in the shade of the forest.
711
00:44:04,640 --> 00:44:07,640
But before this mother
takes her cubs back to the woods,
712
00:44:07,720 --> 00:44:10,160
she has one more trick to teach them.
713
00:44:10,240 --> 00:44:12,520
How to keep cool in the hot sun.
714
00:44:13,480 --> 00:44:14,840
ANDERSON: These little patches of snow
715
00:44:14,920 --> 00:44:17,320
that are left from the snow drifts
from the winter
716
00:44:17,800 --> 00:44:20,840
are everything for these bears,
'cause really, they're AC units,
717
00:44:20,920 --> 00:44:22,200
'cause the hotter it gets,
718
00:44:22,280 --> 00:44:24,440
they really could seek out
these snow fields
719
00:44:24,520 --> 00:44:26,680
just to go and lay their bellies on
and cool down.
720
00:44:35,160 --> 00:44:36,160
[ANDERSON LAUGHS]
721
00:44:36,680 --> 00:44:38,520
That's the best thing,
they're so playful,
722
00:44:38,600 --> 00:44:40,320
so full of energy and just...
723
00:44:41,080 --> 00:44:42,520
They'll roll around like that for hours.
724
00:44:46,280 --> 00:44:49,680
You know, they're using that snow
like a Slip'N Slide,
725
00:44:49,760 --> 00:44:53,120
just like kids
playing on toboggans and sleds.
726
00:44:53,960 --> 00:44:55,680
ANDERSON: They're startin' to learn
how to use their claws
727
00:44:55,760 --> 00:44:57,640
and their paws and get their balance,
728
00:44:57,720 --> 00:45:00,200
and if you look around out here,
I mean, this is pretty rugged terrain,
729
00:45:00,280 --> 00:45:03,120
so they better get their feet
underneath them pretty quick.
730
00:45:03,920 --> 00:45:06,560
I really believe
that they like to have fun,
731
00:45:06,760 --> 00:45:08,160
just like any kid.
732
00:45:09,880 --> 00:45:13,880
ARYEE: But these snowy playgrounds
will soon disappear
733
00:45:13,960 --> 00:45:16,800
as temperatures
are now climbing every day.
734
00:45:20,320 --> 00:45:23,880
HUMBLE: In late June, we hit 30 degrees.
735
00:45:24,880 --> 00:45:27,200
The snow pack is collapsing.
736
00:45:33,160 --> 00:45:36,800
The great Yellowstone thaw
reaches its peak.
737
00:45:50,240 --> 00:45:54,240
Thousands of tons of melt water
cascade through the canyons,
738
00:45:56,080 --> 00:45:58,960
bulldozing everything in their path
739
00:45:59,040 --> 00:46:01,440
and crashes on into the valleys.
740
00:46:07,080 --> 00:46:13,120
Over 250 cubic metres of water
is passing through the river per second.
741
00:46:20,440 --> 00:46:24,720
This melt water is vital
for the regeneration of the land.
742
00:46:30,120 --> 00:46:31,840
But it comes at a cost.
743
00:46:34,600 --> 00:46:36,160
Despite the floodwater,
744
00:46:36,240 --> 00:46:40,960
Yellowstone's residents have to continue
their daily quest to find food.
745
00:46:41,680 --> 00:46:44,840
Biologists have just told us
that a herd of bison
746
00:46:44,920 --> 00:46:49,400
is attempting a river crossing
not far from Yellowstone Falls.
747
00:46:50,480 --> 00:46:51,640
[LOW BELLOW]
748
00:46:52,480 --> 00:46:56,760
Our camera team arrives
to find a two-month-old bison calf
749
00:46:56,840 --> 00:46:58,360
already struggling.
750
00:47:09,240 --> 00:47:11,840
It's been swept away from its mother.
751
00:47:13,800 --> 00:47:15,120
[LOUD BELLOW]
752
00:47:17,080 --> 00:47:19,320
Without her body to shield it,
753
00:47:19,440 --> 00:47:23,160
the calf is pounded
by the full force of the current.
754
00:47:23,360 --> 00:47:24,560
[LOUD BELLOW]
755
00:47:30,400 --> 00:47:33,440
The other females
have their own young to protect.
756
00:47:33,520 --> 00:47:35,960
This one is on its own,
757
00:47:37,720 --> 00:47:39,680
and it's losing energy fast.
758
00:47:59,160 --> 00:48:04,440
But the exhausted calf makes it safely
to the new pastures on the other side.
759
00:48:07,360 --> 00:48:09,080
This one is lucky.
760
00:48:13,840 --> 00:48:18,120
And further south,
the Snake River is also running high.
761
00:48:18,200 --> 00:48:20,200
There's so much floodwater,
762
00:48:20,280 --> 00:48:23,360
that one of the beaver's dams has burst.
763
00:48:24,520 --> 00:48:26,000
JAMES: Yeah, this is off, isn't it?
764
00:48:26,080 --> 00:48:28,920
Look at that. I mean,
it's just blown out, isn't it?
765
00:48:29,000 --> 00:48:30,280
ARYEE: Wow.
766
00:48:30,360 --> 00:48:32,160
Yeah, that is completely busted.
767
00:48:32,240 --> 00:48:33,720
-JAMES: Yeah.
-No, that water is flow...
768
00:48:33,800 --> 00:48:35,440
And it's a lot faster as well.
769
00:48:35,520 --> 00:48:37,160
JAMES: But do you know what?
You're not gonna stop this.
770
00:48:37,240 --> 00:48:39,160
You know, the river has got
to come down here, hasn't it?
771
00:48:39,240 --> 00:48:40,760
So it's either going to
bust through the dam,
772
00:48:40,840 --> 00:48:42,000
or it's going to go
over the top of the dam,
773
00:48:42,080 --> 00:48:43,440
-or it's going to go 'round the dam.
-Yeah.
774
00:48:43,520 --> 00:48:45,360
And this dam just obviously
wasn't quite strong enough.
775
00:48:45,480 --> 00:48:46,520
It's just bust through it.
776
00:48:46,920 --> 00:48:50,200
And you know, when this dam busts,
it's gonna take out the next dam.
777
00:48:50,320 --> 00:48:52,080
You know, it's kind of a domino effect.
778
00:48:52,880 --> 00:48:55,080
JAMES: Oh, yeah! I mean, that is strong.
779
00:48:55,160 --> 00:48:57,280
So there's no way this can,
780
00:48:57,400 --> 00:48:59,280
you know, a pile of sticks
is gonna stop this.
781
00:49:00,120 --> 00:49:02,600
ARYEE: Are they even gonna bother
to fix that bit?
782
00:49:02,680 --> 00:49:04,440
JAMES: No, I don't think they will,
because...
783
00:49:04,520 --> 00:49:07,000
Well, actually, you know,
it'd be impossible to fix it.
784
00:49:07,080 --> 00:49:08,240
-ARYEE: Yeah.
-They're not gonna do it.
785
00:49:08,320 --> 00:49:11,800
I reckon they'll wait, you know,
a month, maybe, or more
786
00:49:11,880 --> 00:49:15,440
till the water goes right back down
to pre-flood level,
787
00:49:15,520 --> 00:49:17,240
then they'll build it back up.
788
00:49:17,320 --> 00:49:20,000
ARYEE: You know, it doesn't look
like much when you look upstream,
789
00:49:20,320 --> 00:49:24,440
but right here, all this water
is pushing up against my body
790
00:49:24,520 --> 00:49:25,800
and there's so much force,
791
00:49:25,880 --> 00:49:28,000
and that's what the dam
is having to contend with,
792
00:49:28,080 --> 00:49:30,000
that's what it's trying to hold back.
793
00:49:31,120 --> 00:49:32,880
If this dam has bust,
794
00:49:34,480 --> 00:49:36,560
what's happened to the beavers?
795
00:49:53,280 --> 00:49:55,720
The beavers are busier than ever.
796
00:49:55,800 --> 00:49:58,560
The water is flowing
right over the top of their dam,
797
00:49:59,320 --> 00:50:01,600
but at the moment, it's still holding.
798
00:50:02,920 --> 00:50:05,600
They won't be able to fix it
until the water levels fall.
799
00:50:17,560 --> 00:50:19,080
Inside the lodge,
800
00:50:19,160 --> 00:50:21,840
all the old bedding
is pushed into the water.
801
00:50:23,800 --> 00:50:25,480
They leave it to soak for a while,
802
00:50:26,400 --> 00:50:29,880
and when it's clean,
they drag it back in,
803
00:50:29,960 --> 00:50:32,520
giving them fresh new bedding
for the summer.
804
00:50:39,080 --> 00:50:41,920
With temperatures
now reaching 30 degrees,
805
00:50:42,000 --> 00:50:44,280
the owl chicks are struggling.
806
00:50:45,200 --> 00:50:47,400
One has already left the nest.
807
00:50:48,560 --> 00:50:51,080
These are birds that thrive
in colder temperatures,
808
00:50:52,160 --> 00:50:56,040
but their nest is now exposed
to the full force of the sun.
809
00:50:59,080 --> 00:51:01,640
Great grey owls struggle to lose heat,
810
00:51:01,720 --> 00:51:04,680
so the remaining two chicks
must leave the nest
811
00:51:04,760 --> 00:51:06,200
as quickly as they can.
812
00:51:06,480 --> 00:51:08,000
[PANTING]
813
00:51:09,920 --> 00:51:12,720
HOGAN: [WHISPERING] The second chick
is getting up on the lip,
814
00:51:12,800 --> 00:51:14,640
on the highest point of the nest,
815
00:51:14,840 --> 00:51:17,160
and just flaps like crazy.
816
00:51:17,240 --> 00:51:18,720
He's looking over the edge,
817
00:51:18,840 --> 00:51:21,200
and this is what they do
before they jump.
818
00:51:22,880 --> 00:51:25,280
ARYEE: But the chicks are vulnerable.
819
00:51:25,360 --> 00:51:27,760
Their wings aren't strong enough to fly.
820
00:51:28,440 --> 00:51:33,240
When they jump, they'll plummet
ten metres to the forest floor.
821
00:51:34,480 --> 00:51:36,560
[WHISPERS] Oh, he's gonna go,
he's gonna go!
822
00:51:36,640 --> 00:51:37,960
Jump, jump!
823
00:51:40,520 --> 00:51:42,120
Go, go, go, go. Oh!
824
00:51:42,760 --> 00:51:45,280
He's leaning way over the other edge!
825
00:51:45,680 --> 00:51:47,000
Could go any second!
826
00:51:50,440 --> 00:51:53,800
ARYEE: It's the riskiest moment
of this owl's life.
827
00:52:00,520 --> 00:52:01,680
[RUSTLING]
828
00:52:02,160 --> 00:52:05,040
It's not the most graceful
maiden flight,
829
00:52:05,120 --> 00:52:07,640
but it's success nonetheless.
830
00:52:07,720 --> 00:52:09,920
HOGAN: [WHISPERING]
He's hanging upside down!
831
00:52:10,440 --> 00:52:11,760
Got it all messed up.
832
00:52:12,360 --> 00:52:14,040
Oh, he is struggling.
833
00:52:15,160 --> 00:52:17,640
It's hanging by one talon.
834
00:52:19,320 --> 00:52:20,920
There he goes!
835
00:52:25,040 --> 00:52:28,160
It's one thing to launch,
it's another thing to land.
836
00:52:30,880 --> 00:52:32,440
ARYEE: The chick lands safely,
837
00:52:33,440 --> 00:52:35,720
but it must head straight back up
into the tree tops,
838
00:52:36,440 --> 00:52:38,640
away from predators on the forest floor.
839
00:52:42,120 --> 00:52:44,960
With Yellowstone's climate
getting warmer each year,
840
00:52:45,040 --> 00:52:48,680
these owls may not be able to live here
for much longer.
841
00:52:54,000 --> 00:52:57,200
Summer temperatures
are becoming too hot.
842
00:53:02,840 --> 00:53:04,760
She's doesn't know what to do,
where to go.
843
00:53:06,440 --> 00:53:08,480
ARYEE: The runt is now in danger.
844
00:53:10,400 --> 00:53:13,920
She's being struck directly
by the intense heat of the sun.
845
00:53:16,160 --> 00:53:17,440
In these conditions,
846
00:53:17,520 --> 00:53:20,560
great grey owls struggle
to regulate their body temperature.
847
00:53:20,720 --> 00:53:22,720
[PANTING]
848
00:53:29,920 --> 00:53:32,480
Panting helps her to cool down,
849
00:53:33,400 --> 00:53:37,000
but her downy feathers,
which are so efficient in cold weather,
850
00:53:37,360 --> 00:53:38,760
may prove fatal.
851
00:53:39,320 --> 00:53:40,720
[PANTING FASTER]
852
00:53:43,880 --> 00:53:44,880
[CHIRPS]
853
00:53:45,880 --> 00:53:48,160
[SIGHS] That little girl's up again...
854
00:53:48,720 --> 00:53:50,400
Finally, but,
855
00:53:51,440 --> 00:53:55,600
she's hot too.
She wants out of that heat, I can tell.
856
00:53:55,960 --> 00:53:59,960
ARYEE: This is a leap of faith
she has got to make.
857
00:54:04,840 --> 00:54:08,200
She's back on the launch pad.
This is where I think she's gonna go.
858
00:54:12,040 --> 00:54:13,160
She's...
859
00:54:25,560 --> 00:54:26,880
She launched!
860
00:54:26,960 --> 00:54:28,200
She launched!
861
00:54:30,040 --> 00:54:31,040
[CHIRPS]
862
00:54:34,800 --> 00:54:40,560
HOGAN: So this forest is now home
to three more great grey owls.
863
00:54:41,040 --> 00:54:42,400
I'm impressed.
864
00:54:42,600 --> 00:54:44,200
I'm proud of this little girl.
865
00:54:45,240 --> 00:54:48,200
You know, maybe one day
she's gonna just come back here
866
00:54:48,280 --> 00:54:51,840
and raise a great grey owl family
of her own.
867
00:55:06,320 --> 00:55:09,200
HUMBLE: As the longest day
of the year approaches,
868
00:55:09,280 --> 00:55:11,320
spring becomes summer.
869
00:55:12,360 --> 00:55:13,640
The animals we've followed
870
00:55:13,720 --> 00:55:17,200
have made it through
Yellowstone's most challenging season.
871
00:55:18,720 --> 00:55:23,040
This year, the thaw started
three weeks earlier than usual...
872
00:55:26,160 --> 00:55:30,680
An area of 30,000 square miles
has been transformed...
873
00:55:34,560 --> 00:55:38,280
And the mountains have released
over a millions tons of water.
874
00:55:40,440 --> 00:55:43,720
And finally, from top to bottom,
875
00:55:43,800 --> 00:55:46,360
Yellowstone is free of snow.
876
00:55:47,160 --> 00:55:50,560
Now our animal families
face the new challenge of summer,
877
00:55:50,640 --> 00:55:53,520
when temperature can soar
and vegetation wither.
878
00:55:54,840 --> 00:55:57,160
And that leads to a new threat,
879
00:55:57,920 --> 00:55:59,400
wildfires.
72488
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