- 7 months ago
Documentary, Yellowstone - Wildest Winter to Blazing Summer - The Wildest Winter
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AnimalsTranscript
00:00Stretching out before me is the magnificent Yellowstone.
00:17This is one of the most dynamic, unpredictable and exciting environments on Earth.
00:30Deep in the Rocky Mountains, this vast wilderness is home to North America's most iconic wildlife.
00:43But every year, Yellowstone's animals are pushed to their absolute limits.
00:50Temperatures can swing from minus 40 in winter to approaching plus 40 in summer.
00:57And at the heart of this change is the thaw.
01:02This melt can last several months from March to July and is one of the most dramatic seasonal events on Earth.
01:10How do the animals cope with such extremes of temperature?
01:19We're here to find out.
01:21I'm joined by biologist Patrick Ayi.
01:28That's intense.
01:30And a team of wildlife cameramen and expert scientists.
01:34I'll be following some of the area's key wildlife.
01:39We'll be getting to know families through their highs and lows starting right now.
01:44And I'm looking at the bigger picture, understanding the science of the thaw during each season across winter, spring and summer.
01:56That's brilliant.
01:58Living here is tough.
02:00The changing climate has brought freak storms, flash floods and raging fires, making life for the animals even more extreme.
02:15With unprecedented access to this remarkable place, over the next three nights, we're bringing you Yellowstone as you've never seen it before.
02:23Welcome to Yellowstone, the wildest winter.
02:46It's early March.
02:47This is a world blanketed in thick snow and ice.
02:57And after four long, hard months of winter, the animals still have more weeks of brutal cold to endure.
03:08We're in the northwest of the USA, 2,000 meters up in the Rockies.
03:13This is an area known as the Greater Yellowstone ecosystem.
03:18It's the size of Scotland, includes two national parks and is bounded on three sides by mountain ranges.
03:29In this program, we'll be following the lives of animals that have to adapt to extreme change.
03:35As winter turns into spring.
03:38For many, this is the ultimate challenge.
03:42Particularly for Yellowstone's biggest, and at this time of year, hungriest carnivores.
03:50Patrick's heading high up into the mountains on their trail.
03:53It's amazing to think that somewhere out there are grizzly bears.
04:05But it's right at the tail end of winter and it's really cold, so most of those bears are still going to be hibernating in dens deep beneath the snow.
04:13And for most, that's a sensible strategy.
04:17Right now, the weather is bitterly cold and down to minus 21 degrees Celsius up here.
04:24It's usually later in March that the majority of grizzlies start coming out.
04:28I'm in the Gallatin Mountains in the northwest of Yellowstone.
04:41Our grizzly expert, Casey Anderson, is out here monitoring bear activity.
04:46Hi, Casey. How you doing, man?
04:48Good.
04:50We're looking for any bears that are emerging from hibernation early.
04:53And the most likely place to find them is at the higher elevations where grizzlies have their dens.
05:01Good view, huh?
05:03Absolutely stunning.
05:05But it does look completely devoid of life.
05:07How are you even going to start looking for these bears?
05:10You're right. There's not much moving around out here.
05:13Right now, the only bear that probably will be out is those first big males.
05:18Casey believes some grizzlies are already leaving their dens because of a recent spell of unseasonably mild temperatures.
05:27So just a few days ago, we had really warm weather and it felt like spring.
05:31It's been so warm.
05:33You've got to believe the bears are thinking, it's getting close to spring.
05:36And that can be really bad news because it's not spring.
05:39And they come out here and winter could hit again.
05:43And that could really be devastating to a lot of animals, including the bears.
05:47Last week, right here, it was 15 degrees warmer than today.
05:54Now it's back to more typical March conditions.
06:00Whoa.
06:01This is pretty intense.
06:03That's intense.
06:05How do the bears cope with this?
06:07Bears are tough, but this is difficult for them too.
06:11Suddenly, Casey sees an opening that could be a bear den.
06:15Is he like these natural rock formations?
06:17Yeah, it's like a little cave.
06:18Yeah.
06:20It's perched high on a steep slope.
06:23Not easy going.
06:25Oh, man.
06:27Oh, man.
06:28Oh, man.
06:30Oh, man.
06:32Oh, man.
06:34Oh, man.
06:35Oh, man.
06:36Oh, man.
06:37Oh, man.
06:38Oh, man.
06:39Oh, man.
06:40Oh, man.
06:41Oh, man.
06:42Oh, man.
06:43Oh, man.
06:44Oh, man.
06:45Things I'll do for bears.
06:51Would that be a good sight for a bear to high-bait him?
06:58The statistics are this.
06:5970% bears will dig in a north face slope.
07:03At least 30% of this population
07:06it does something else.
07:08And something else is something like this.
07:11something like this already made in the sun didn't get down in there and trap the heat
07:18it's perfect and it's not all one big sleep during hibernation the pregnant females also
07:26give birth it's march now and those little guys are born two months ago so yeah just imagine these
07:33little guys that big they're gonna grow to be about that again about another month and then
07:39in another month from now they're gonna pop their heads out and this is going to be home and it's
07:43it's just amazing think about that the first view it's a pretty good one we head off before we disturb
07:51any sleeping bears emerging in these conditions would mean the odds are against them
08:09and 50 miles further east that's exactly what's happened scientists have tipped off one of our
08:18camera teams about a grizzly bear that has taken the risk of emerging early it's clearly struggling
08:26the warmer weather of a week ago has been followed by plunging temperatures and more snow this could
08:37make finding food impossible the grizzly finally makes it down from the mountains to the valley floor
08:48there are plenty of bison here but even a starving bear won't tackle these formidable beasts
08:58bears rely heavily on their extraordinary sense of smell to find food
09:07their nose bristles with over a billion nerve cells
09:12it's their super sense
09:16and it's led this bear to a pond
09:21a dip in the subzero water could zap his precious energy
09:48grizzlies are superb at catching fish
09:56but it's not fish he's after
10:00it's a bison
10:09long dead
10:12frozen all winter
10:14and now released
10:16from its icy tomb
10:17this is probably the first meal the bears eaten in over four months
10:26it offers a huge protein hit
10:30but he'll need to hang on to it
10:34the carcass's smell attracts scavengers
10:38these coyotes won't fight the bear
10:45he's 15 times their weight
10:48but they will harass him for scraps
10:51he tries to mask its scent
10:58by covering it with grass
10:59this will also slow down the bison's decay
11:11having lost up to a third of his body weight during hibernation
11:14he's determined to keep these precious nutrients for himself
11:19despite emerging from his den early
11:36this lone bear has hit the jackal
11:42but the stakes are high
11:56and the majority of grizzlies won't bother venturing out
11:59until the consistent warm weather of spring
12:03but that still seems a long way off
12:12the snow shows no sign of letting up
12:18all the animals here face the same basic challenge
12:29finding enough food to survive until spring
12:33our crews are out across the region
12:37to capture the stories of how the wildlife is coping
12:41yellowstone's elevated position
12:55and horseshoe of mountains
12:57channel and trap the cold air driving in from the north
13:01and moisture coming in from the pacific ocean
13:04this leads to prolonged periods of extreme weather
13:10when the snow melts in spring
13:22it feeds into a thousand rivers and streams across yellowstone
13:26these two and a half thousand miles of running water
13:30are hugely important
13:32not just for yellowstone
13:34but they provide an essential resource
13:37for millions of people and animals
13:39right across the western united states
13:42scientists constantly monitor
13:47how much snow is building up here during the winter
13:50to understand what's going on this year
13:54i'm joining a team up in the bear tooth mountains
13:57in the northeast
13:58on their cool commute to work
14:01this is possibly the best office i've ever been to
14:08this looks like a pretty good spot
14:11oh wow that's right about 205 centimeters
14:19okay
14:21lukas zukevich is one of the hydrologists who spends the winter carrying out health checks on the snow
14:27our entire history of our snowpack starting mid october is really in this snowpack here so we're going to dig a hole down to the ground and it's pretty much the coolest layer cake that you're ever going to see
14:34i love that i have a feeling i might be here for months right okay so
14:41i have a feeling i might be here for months right okay so
14:48yay i picked her off
15:02that is so cool i have to say coming from a country where you know if you get four centimeters of snow it's newsworthy
15:10to look at that and to to kind of understand that that is a record of your winter that's quite cool isn't it it's amazing and the best part of this job is it's never the same every year is different it's like hitting the reset button on it every year
15:27so it's time for us to analyze what the snowpack can tell us
15:32so looking at it from bottom to top here we're looking at a time series so we have
15:38our early season october snowfall probably our thanksgiving and christmas snowfall that we have here
15:43you had a white christmas we had a white christmas this year it was great
15:47various measurements enable lucas and his team to work out how much snow is building up here and how dense it is
15:55the texture of it here is completely different it feels much more compact exactly as when we were digging it out
16:03the density reflects how much water is contained in each layer of the snowpack and that varies depending on the temperature when the snow fell
16:13maybe we see some pretty well bonded snow in here which is generally an indication of warm temperatures
16:18okay warm temperatures actually bond the snow pretty well together
16:21first of all we're going to stick one right up here on the surface of the snow
16:24measuring the temperature is also key in helping to predict when the bulk of the water will flood down into the valleys
16:31and the next one at 170 we're going to stick that right below that little crest layer that we saw
16:36and these readings also provide clues as to why some mammals hibernate deep in the snow
16:42in the snow stick it right in the ground in the grass so we can see here that our snow surface temperature
16:50what does that one say i would say minus eight but as we move further down in the snowpack it's warmer
16:56it's warmer it's minus three degrees that's mad okay and if we go even closer to the ground
17:02it's almost on zero yep so the ground is generally close to zero degrees celsius through the winter
17:08so the snowpack is also insulating the soil but it also makes sense when you look at something like a grizzly bear
17:15hibernating in the winter beneath the snow i now understand why it chooses to hibernate there because it's warmer
17:23snow caves are pretty warm that's brilliant
17:27this insulating effect not only allows bears to hibernate in snow dens it keeps the grass alive vital food for herbivores
17:37and whilst it may look just like a white wall we're actually looking at an enormous reservoir
17:44when the weather warms up enough to heat the snowpack right through
17:51billions of liters of water run off the mountains into the rivers and lakes of yellowstone
18:00is the timing of the thaw important for you it is because it affects when we see the bulk of the water move into our river systems
18:07right this is our reservoir that we have in our mountains this is how we get our water this is how it flows through the park
18:15so do you think when the thaw comes it's going to be a normal year or an abnormal year
18:22we're slightly below average with the snowpack that we have here in place at this elevation
18:27but really it's going to be the next month or two and the weather that we experience
18:31that's going to dictate what we see this year in terms of our thaw and how that impacts the bigger ecosystem
18:36it will be interesting to see what happens in the coming weeks as the weather has already proved highly volatile this winter
18:46there was a jump in temperatures and an unusually warm period at the end of February
18:52March has now seen a return to the colder more typical weather for this time of year
18:57in recent years yellowstone has experienced milder winters more often and this one appears to be following that trend
19:09Patrick has headed south to see how the temperature jumps this year are affecting another iconic species
19:18snow is a lot more complex than it looks and for one animal a bird of prey the precise depth and type of snow
19:30can literally mean the difference between life and death
19:34this is the great grey owl one of the largest owls in the world with a wingspan that stretches up to 1.5 meters
19:57it's a winter specialist it survives in some of the coldest forests on earth
20:03from Siberia to Scandinavia
20:08to here in Northwest America
20:12researchers believe several hundred great grey owls live in the Jackson Hole Valley
20:17all within 150 square miles of forest
20:28our cameraman Jeff Hogan has had a lifelong love affair
20:32with this enigmatic bird
20:39I've been following and filming the great growls for just about 30 years now
20:44it's still just as exciting and challenging as it was the very first day
20:49so this is a fantastic place for owls to be hanging out
20:53I mean it's mixed aspens and conifer forest along with these meadows provide an incredible habitat for the prey that the owl feeds upon
21:06Great greys feed on rodents mainly gophers and voles that burrow under the snow
21:12their huge facial discs act like satellite dishes directing sound to their ears
21:22their hearing is exceptional
21:26they can detect prey from over a hundred meters away through snow almost half a meter deep
21:31but it's one thing knowing where to pounce
21:36another to break through to reach the meal
21:39Jeff is out looking for them
21:42he's concerned that with the erratic weather conditions
21:45the owls face a big challenge
21:48earlier this week we got a lot of snow
21:50and then the sky's cleared
21:53so you can look around here and see where the sun is beating down on the surface of the snow pad
21:58and it really softens it up
22:00it doesn't melt it completely but it makes it really soft and wet
22:03and then at night when the temperatures plummet
22:06it'll freeze hard like and turn it to ice
22:09and you can actually see this layer of crust
22:11well you can really feel that
22:17I mean ouch
22:19this is hard
22:22and as the temperatures drop
22:24as night approaches this is going to get harder and harder
22:28and these owls have to bust through this crust
22:31and then maybe another foot of snow to get at their prey
22:36Jeff hasn't seen any great greys
22:38which could mean they've been forced further afield to hunt
22:42so I guess I'm going to have to just keep on looking
22:48at this time of year eating enough food is critical
22:52if the great grey owls can't hunt
22:55they simply won't lay eggs
22:57or even nest this season
22:59their population is already small and vulnerable
23:03biologist Catherine Goura is keen to see how current snow conditions might be impacting the owl's ability to feed
23:13and that involves a simple experiment
23:17Catherine you're stood out here with a ruler or meet a rule and these flasks of water
23:23what do these have to do with owls?
23:25so this is about the same weight as a great grey owl
23:29so what we're doing is dropping these
23:31and we're seeing how far they penetrate the snow
23:34because it in turn can show us how easy or hard it is for great grey owls to penetrate the snow to get to their prey
23:40right Catherine can I give you a hand?
23:42absolutely
23:44so what do I do?
23:45from one metre above the snow
23:47okay
23:48so that's right here
23:49one metre that's here?
23:50yep
23:52okay so it hasn't really gone that far
23:53it's gone about
23:55what 17 centimetres
23:58with their prey often underneath twice as much snow
24:01this is why the owls are having trouble feeding
24:04our concern is that it's changing the timing of their behaviour
24:08so if there's not enough prey
24:10I mean that's probably going to spell disaster
24:12are you worried about that?
24:13I definitely am
24:14I've been working with these owls for years
24:17I love watching them throughout their nesting season
24:19and it really concerns me
24:20if they're not going to be able to have enough prey
24:23to even attempt to nest or to eventually support their young
24:30this year with the tricky snow conditions
24:33the owls appear to be suffering
24:36to find out how they're really getting on
24:39or indeed if they're around at all
24:41Catherine needs to conduct her survey at night
24:47the night time call of the great grey owl
24:50is one of the early signs of spring
24:52and for scientists this is the first time
24:55they'll be able to work out exactly where they are
24:57what they're up to and how they're doing
24:59if the great greys are going to be successful
25:02in raising chicks
25:03they should be out there right now
25:06and we hopefully should be able to hear them
25:08but the thing is this year nothing is certain
25:13Geoff has also joined us
25:15he's hoping his luck finding owls will change under the cover of darkness
25:19the survey area covers several square miles
25:30now my top speed in snowshoes is half a mile per hour
25:35this could be a long night
25:37all right this looks like a good spot to stop and survey
25:43okay so what are we going to do?
25:46so I'll do the male territorial call
25:48and then we'll want to be as quiet as possible
25:50and we'll listen to see if one responds
25:52all right so fingers crossed
25:53fingers crossed
25:54okay
25:55okay now
25:56I'll do my best
25:57mmm
25:58mmm
25:59mmm
26:00mmm
26:01mmm
26:02mmm
26:03mmm
26:05mmm
26:10yep that's it
26:12right here
26:13yeah this is great
26:17responding
26:20so is that probably a male?
26:22so that's a male territorial call
26:24right
26:25so they'll do that either to attract a mate
26:27and also to tell other males that this is his zone
26:30his territory
26:31should I give it a go?
26:32mm-hmm
26:33you should do it
26:35woo!
26:36no that's too deep
26:38see if he likes it
26:40woo!
26:41woo!
26:42woo!
26:43woo!
26:44woo!
26:45woo!
26:46woo!
26:47woo!
26:48woo!
26:49woo!
26:50woo!
26:51woo!
26:52woo!
26:53woo!
26:54woo!
26:55woo!
26:56woo!
26:57woo!
26:58it's really given the conditions that we're having this year
27:00this is a really good sign that we can hear the great grey owls
27:03mm-hmm
27:05I was definitely worried with kind of the hard crust we've had that they might not be on territory yet
27:10but it's a good sign that they're here and defending it
27:12woo!
27:13woo!
27:14woo!
27:15woo!
27:16woo!
27:17so there are males out there and they're defending their territory
27:21given this year's unpredictable weather it's a promising sign
27:24Jeff and Catherine will continue monitoring and we'll be back to see how the owls are getting on later in the season
27:33woo!
27:34woo!
27:35woo!
27:36woo!
27:37woo!
27:38woo!
27:39woo!
27:40woo!
27:41woo!
27:42woo!
27:43woo!
27:44woo!
27:45woo!
27:46woo!
27:47all across the region the challenge for much of the wildlife is simply to hang on until spring
27:53it may appear that animals like bison spend the winter stoically struggling through the snow
28:00but there is a respite for some and it's thanks to a feature that is synonymous with yellowstone
28:13it's famed not just for its landscapes and its wildlife but also for its geology
28:20yellowstone has more geysers than anywhere else in fact 60% of all the geysers in the world are here
28:27and the reason for that is a giant magma chamber literally a pool a sort of lake of molten rock
28:35sitting just below the earth's crust literally right under my feet here
28:39scientists believe there's enough magma down below to fill the grand canyon more than 11 times
28:56and in west yellowstone there's plenty of evidence of all this geothermal activity particularly with the dramatic geysers
29:06these hot springs intermittently send fountains of water and steam into the air
29:13it looks a fairly inhospitable landscape but around 200 bison spend the winter living and feeding here
29:22these bison are part of what is known as the central herd and they don't need to work nearly so hard to get at the vegetation beneath the snow
29:30the earth here is warmed by that magma chamber bubbling away beneath the crust
29:37and that means there's far less snow and the vegetation is much easier to get at
29:43but scientists have discovered that these easy pickings come at a high price
29:49the hot water pushing up from deep underground dissolves the chemical compound
29:56silica from the volcanic rock and deposits it on the grass
30:01now silica coats the vegetation around geysers and hot springs
30:05and it's a little bit like eating something that has been covered in a very fine dusting of ground glass
30:11it's enormously abrasive and very very tough on the teeth
30:18the other issue is the high levels of fluoride in the water
30:22this chemical is a by-product of historic volcanic eruptions
30:26in low doses such as in toothpaste it's good for your teeth
30:31but here it's so concentrated it actually softens rather than strengthens the enamel
30:38now the combination of silica and an excess of fluoride in their diet means that the bison down here
30:45lose their teeth significantly earlier than the bison up in the north of the park
30:50in fact life expectancy amongst this herd is at least five years less
30:57so although these bison have an easier life than their snow-bound cousins
31:02it's definitely a much shorter one
31:07finally by mid-march other parts of yellowstone also get a reprieve from deep snow
31:14it's melting faster than it's falling
31:22warmer air has come up from the south and pushed out the cold front in the north
31:28daytime temperatures rise above freezing unlocking the rivers
31:34and the animals make the most of it
31:41underwater plants are more nutritious than those beneath the snow
31:44and are a vital food source for this moose
31:47which needs to pile on the pounds fast
31:53this muskrat is enjoying the vegetation too
31:56his double layer of waterproof fur keeps him warm and dry even whilst eating on an icy platform
32:03and when he dives down his lips seal shut behind his big rodent teeth so that he can gather food without swallowing water
32:11even a winter casualty is good news this elk carcass will sustain many scavengers over the coming days
32:26and it may be here thanks to yellowstone's most charismatic predator
32:33thanks to yellowstone's most charismatic predator
32:40yes
32:48oh my god look at the wolf
32:51this is the most
32:53this is the most incredible view
32:58This is the most incredible view.
33:02And what becomes so evident when you see a pack of wolves running across snow like that
33:08is just how perfectly adapted they are as winter predators.
33:15There are some things that in life floor you.
33:21And seeing a pack of wolves are completely, completely overwhelmed by the sight.
33:45To see what effect this year's Thor is having on these animals,
33:49I'm joining wolf biologist Doug Smith.
33:54We're on our way up a ridge on Blacktail Butte in the Northern Range,
33:58home to a pack of 11 individuals that lay claim to a territory of 250 square miles.
34:06Doug and his team constantly monitor the wolves in Yellowstone.
34:11He's concerned that climate change is having an impact on them.
34:19They just ooze charisma, don't they?
34:24Even two kilometers away.
34:28It's true.
34:29There's something enchanting and mysterious about them that has gone through the ages.
34:46Usually, wolves thrive in the winter.
34:50They're snow specialists.
34:51Their feet fan out, enabling them to run across deep snow at over 25 miles an hour.
35:02This gives them an advantage over their prey, elk and bison,
35:06which struggle with their cloven hooves.
35:13Wolves generally have even more of an edge in March,
35:16when Yellowstone's herbivores are weak and hungry.
35:24But this year is different.
35:28By Yellowstone's extreme standards,
35:312016 has been one of the mildest winters ever recorded.
35:36Temperatures have fluctuated wildly,
35:39but overall they've hovered three degrees above the historic average.
35:43A warmer winter is great for herbivores,
35:48as there's less snow and they're less likely to die of cold.
35:55But for their predators, Yellowstone's wolves,
35:58it can make life a lot more difficult.
36:03Because this winter has been so mild,
36:06do you think that that is going to have a big impact on these wolves?
36:12It certainly could.
36:13I mean, hard winters wear your prey down,
36:15and that makes them easier to kill for wolves.
36:18A mild winter, the prey is going to do a little bit better.
36:21This winter was warmer and below average snowfall,
36:25and it's early to tell what the effect of that is,
36:28but we think that wolf food consumption rates,
36:32kill rates, are down because of that.
36:34So these milder winters favor the prey,
36:37and so does that mean fewer pups,
36:40which leads to smaller packs?
36:43This change in winter weather could be a huge impact.
36:48Wolf kill rates are down this year,
36:51but our camera teams across the region have caught some hunts on film.
36:55Perhaps there will be clues as to the problems wolves are facing right now.
37:01Talk me through what's going on here.
37:04I mean, that's classic wolf hunting behavior.
37:08What wolves are looking for are behavioral cues
37:12that indicate to them that there's a weak bison.
37:15Right.
37:15But what's interesting is the bison are staying in these areas
37:19where there's either no snow or little snow
37:22because they've got firm footing and they feel confident.
37:26And so what the wolves are doing is trying to bump them
37:29into a place that's more favorable to them, i.e. deeper snow.
37:34This winter, there's less deep snow.
37:37So the wolves are having a harder time.
37:39Plus, these brown places have forage for the bison to eat,
37:43so they're going to be healthier.
37:45That's also bad for the wolves.
37:48The next hunt involves the wolves' main winter prey, the elk.
37:53Now here's an elk encounter, and this is even more dramatic.
37:56This female elk is very healthy, and she's actually attacking the wolf,
38:01but she won't leave the dry ground.
38:04Yeah.
38:04Classic example of the importance of snow depth and footing.
38:09Look at the elk.
38:09A healthy elk will always outrun a healthy wolf.
38:14So talking to the old-timers who lived here in Yellowstone
38:17during the 1960s and 1970s,
38:20every winter was a deep snow winter.
38:22It was the rare winter that was not much snow.
38:27Now it's the rare winter where you have deep snow.
38:30It's more common to have shallow snow,
38:32and that's switching this balance between predators and prey.
38:37With so few successful hunts,
38:44scientists have noticed that some of the wolves
38:46are turning to a summer feeding strategy.
38:50Instead of working as a pack, they're hunting alone,
38:53digging into burrows to catch small mammals.
38:56It's much less rewarding, much harder work,
39:02and for this time of year, definitely unusual.
39:08The repercussions could be huge.
39:12The female wolves are pregnant right now,
39:14and poor feeding may lead to weaker pups.
39:17We won't know until early summer.
39:19It's the end of March.
39:31The signs of spring are getting stronger every day.
39:34I guess I weigh more than a coyote.
39:46With temperatures warming,
39:48many more grizzlies are coming out of their dens.
39:51Our bear expert, Casey Anderson,
39:53is out searching for them up in the Gallatin Mountains.
39:58Sometimes it's not that hard
40:00to work out where they've passed through.
40:03If you look,
40:05you can see right here,
40:07it's all kind of wore out.
40:08You can see these little claw marks.
40:14Well, sometimes when the bears come out of the den,
40:17they can be a little mischievous,
40:18and if you look right here,
40:20one of the first stops a bear had made
40:21was this snowmobile seat.
40:23Just ripping, clawing, biting, just plain, really.
40:27It's part of living in grizzly country.
40:29It's never certain when bears will emerge in Yellowstone,
40:35but this year has been more unpredictable than ever.
40:42It's been really a strange year so far.
40:47The spring temperature has definitely gotten a few bears out early.
40:50We know that one bear has gone down,
40:53pulled that bison carcass out of the pond.
40:54That was a risk worth taking.
40:58But it was a risk.
41:00Other early grizzlies may not have been so lucky.
41:05The adaptations animals make in Yellowstone
41:08to chime with its extreme seasonal changes
41:11are finely balanced,
41:13and in tune not just with temperature and degree of snow cover,
41:17but also with length of day.
41:21Right up here,
41:22there's a long-tailed weasel.
41:26He's running around right up here.
41:31So these long-tailed weasels,
41:33as soon as spring actually is here,
41:35they will turn brown,
41:36and they'll be camouflaged for the spring, summer, and fall.
41:39When winter comes again,
41:40they turn white just like this.
41:41The fact that he's still completely white
41:45shows that it's very much winter.
41:48The change in colour is triggered by hours of daylight,
41:52not by temperature.
41:54He won't turn brown until next month.
41:57And just like the fox and the coyotes,
41:59he's looking for all the rodents
42:01that live underneath this snow cover.
42:03He's just tunneling down,
42:05going and grabbing these things
42:06and popping up and eating them.
42:07But whilst he's still white,
42:10if the snow melts too quickly,
42:12he'll lose his camouflage advantage
42:15and could be at risk from predators himself.
42:19And one mammal who would happily eat him is a fox.
42:25You can see this little story unfolding here.
42:28This is a fox doing what they're so good at in the wintertime.
42:33A bear's greatest sense is their sense of smell,
42:35whereas a fox's greatest sense is their sense of hearing.
42:39And they literally hear a little rodent
42:42way down in the snow.
42:43They'll stop,
42:44and you see them,
42:45they'll do that same way
42:45they pitch their head side to side.
42:46And what they're doing is really triangulating
42:49and zoning in the exact location of that rodent.
42:53And then they just do this giant leap up in the air
42:56and get this momentum with gravity
42:58and just poof,
42:59right down through the snow
43:01and grab that little guy.
43:02He doesn't even know it's coming.
43:03He thinks he's down there all protected.
43:06And literally there's a nail up there
43:07there's a fox missile coming straight down
43:10and getting him.
43:10And look at that.
43:11That's quite a ways down.
43:16A little vole is a pretty good snack for a fox.
43:20Whereas for a bear, it's nothing.
43:21And there's no way it could just survive
43:23on voles alone through the winter.
43:24So that's why they choose to hibernate.
43:26There's just nothing out here to eat
43:27if you're a big old bubbling around bear.
43:30Down in the south,
43:41there's also still plenty of snow
43:43in the forest habitat of the great grey owl.
43:47Cameraman Jeff Hogan
43:48has been out night and day tracking them
43:51to find out whether they're breeding successfully.
43:53We have an owl.
44:00Jeff's been hearing and seeing
44:02the male owls consistently,
44:03which is a reassuring sign.
44:07He'd feared they might have left the area
44:09due to a lack of food.
44:13Look at the setup here.
44:15This year, the issue has been icy snow.
44:21It's prevented the great grey owls
44:23snow-plunging deep enough
44:24to catch their prey.
44:32The owls each need at least one rodent a day.
44:36And if they don't eat enough now,
44:38they just won't breed.
44:41He didn't catch anything.
44:45There's something right here underneath him
44:48because he's back.
44:50He's going to make another attempt.
45:01Oh, he jumped.
45:07Oh, he's on the ground now.
45:09I don't think he caught anything.
45:18He just flew up with nothing.
45:22I've been here since dawn
45:24and he hasn't caught anything yet today.
45:26It appears that owls are still struggling.
45:33Then, at last,
45:36a sign of hope.
45:38A female arrives.
45:40This could get exciting.
45:45We've got two great greys right here.
45:47Following one bird
45:48is pretty exciting.
45:51Let's have two birds.
45:54It's amazing.
45:56It really is amazing.
45:58Let's see what goes on.
45:59Oh, here, he's flying in.
46:01Oh.
46:05Mating.
46:06Mating.
46:07Oh, my.
46:11I've never seen this before.
46:17This is great news.
46:20It's incredible.
46:21Absolutely incredible.
46:24The end of March.
46:27Courtship.
46:28Mating.
46:31Next step is nesting.
46:33Eventually,
46:43the pair choose to nest
46:44on an old, broken spruce trunk.
46:49How many eggs are laid
46:50will depend on how much food
46:52the owls consumed
46:53earlier in the season.
46:55On average,
46:57they lay four,
46:58but this year,
46:59it could be less.
47:01We'll be following them
47:02to see what happens.
47:03To see what happens.
47:32It's now April
47:37and the temperatures
47:38are warming up.
47:39This is Jackson Lake
47:40in the Tetons
47:41and normally,
47:42it would be frozen
47:43well into May,
47:44but already,
47:45the ice is breaking up.
47:50The arrival of the melt
47:51is a tipping point
47:53for the wildlife
47:53of Yellowstone.
47:55And this year,
47:56after an extremely mild winter,
47:58it's three weeks early.
48:00At long last,
48:01though,
48:02it's official.
48:03Spring is here.
48:06As the days get longer,
48:08the sun is higher
48:10in the sky
48:10and its increased energy
48:12melts the snow
48:13and raises
48:14daily temperatures.
48:17Although there's still
48:18snow on the ground,
48:19the warming temperatures
48:20are actually changing
48:22the shape
48:23of the crystals
48:24within the snowpack.
48:26Now,
48:27they've turned
48:27into tight little balls
48:29and there's a lot
48:30of water
48:31in between them,
48:32so the packs
48:33become a lot slushier.
48:34It's literally
48:35at melting point.
48:38All this snow
48:39is just water
48:40in waiting.
48:42Millions of tons
48:43will gradually melt,
48:44flooding into the lakes
48:45and rivers
48:46of Northwest America.
48:49It's a process
48:50that will continue
48:51until July.
48:52It's the valleys
48:55that lose
48:56their snow first
48:57and then finally
48:58the mountain peaks
48:59release their
49:00huge reservoir.
49:08Soon,
49:08these warmer temperatures
49:09will lure
49:10the last male grizzlies
49:12out of hibernation.
49:13and with the snow
49:16retreating,
49:17plants too
49:18are bursting
49:18into life,
49:19a nutritious feast
49:21for hungry bears.
49:26Patrick's back
49:27in the Gallatin Mountains
49:28with Casey Anderson
49:29to find out
49:30why a top predator
49:32sometimes chooses
49:33the vegetarian option.
49:37Look right here.
49:39This is a biscuit root.
49:41This is a grizzly favourite.
49:46Bears are omnivores.
49:48They don't just
49:49survive on meat.
49:51Their diet
49:51also includes
49:52insects,
49:53fungi
49:54and lots
49:55of vegetation.
49:57Many bears
49:58time their emergence
49:59to coincide
50:00with biscuit root
50:01coming into flower.
50:03So that
50:03is what they're
50:04looking for right there.
50:05This
50:06bit of root
50:07at the bottom.
50:08There's tons
50:08of calories in them.
50:09So how much
50:10biscuit root
50:10do they have
50:11to get through?
50:12I've watched them
50:12eat hundreds
50:13if not thousands
50:14of these roots.
50:15What does it
50:15taste like?
50:16You tell me.
50:19I was afraid
50:20you were going to
50:20say that.
50:20But I'm up
50:21to the challenge.
50:22Bottoms up.
50:27It's like carrots.
50:29Yeah?
50:29Yeah.
50:30Like kind of
50:31starchy carrot.
50:31Yeah.
50:32To be honest
50:33with you,
50:33when I'm
50:34hiking around
50:34out here,
50:34sometimes I'm
50:35looking at my
50:35backpack and
50:36see what I have
50:37for lunch
50:37and I look
50:37on the ground
50:38and I'm like,
50:38I'm going to
50:38go grizzly style
50:39here and start
50:40digging away.
50:42As they put on
50:43weight after the
50:44winter and more
50:45grizzlies come out,
50:47they begin to
50:48communicate with
50:48each other.
50:50Each male can
50:51have a home range
50:52of over several
50:53hundred square miles
50:54and they need to
50:55work out who else
50:56is out there
50:56on their patch.
51:00So this is an old
51:02backcountry camp
51:03in here.
51:04People come up
51:04and camp from
51:05time to time.
51:05There's a little
51:06tent over here
51:06and this old
51:08outhouse, that's
51:09a tree right next
51:10to it.
51:10It's the rub tree
51:11where these big
51:12males will rub
51:13their back and
51:14urinate all over
51:14the place right
51:15by the outhouse.
51:16So it's a bear
51:17toy though.
51:18It really is.
51:19You can look
51:20here.
51:20There's these big
51:21claws right here
51:23and look right
51:24here, Patrick,
51:25where the sap
51:25stuck, all the
51:27hair stuck to
51:29the tree all
51:30down through
51:30here.
51:32So all this
51:32here, this is
51:35bear hair.
51:36Yeah.
51:38So what they
51:38do, they come
51:38over and they
51:39just usually come
51:40up and put their
51:41back on the tree
51:42and they'll rub
51:43their scent all
51:44and they just
51:44really get in
51:45and they reach
51:46up and grab
51:46like this and
51:47then they bite
51:47the tree and
51:49they drop down,
51:49particularly the
51:50males, and then
51:51they do this
51:52thing I call the
51:52cowboy walk.
51:54So they just
51:54stick it and they
51:55twist it up.
51:55like this.
51:58Real rigid
51:59legs, they just
52:00really twist.
52:02So each bear
52:03who comes to that
52:04tree will step
52:05in that exact same
52:05spot and they do
52:07it over and over
52:08again and it leaves
52:09these big divots
52:10in the ground.
52:11So if you're a
52:11smaller bear and
52:12you have to really
52:13reach for that
52:13next foot divot,
52:15you know there's a
52:16bigger bear in town.
52:17This is a well-known
52:19rub tree.
52:20We're setting up a
52:21camera to see how
52:22many of the big
52:22males are out there.
52:25But see this right
52:26here?
52:26Right.
52:27It's going to take a
52:27recording and it's
52:28going to text me to
52:30my cell phone.
52:30No way.
52:31Yeah, real time.
52:32So as soon as the
52:33bear's there, I'm
52:34getting a text.
52:34So hang on, you're
52:36going to get a text
52:36from a bear?
52:37A few days later, Casey's
52:48called me in to look at
52:49the results.
52:51All right, well, we've
52:51got, let's take a look
52:52and see what it's, what
52:54it's caught.
52:54Uh-oh.
52:59That's just brilliant.
53:01That is an elk, a cow elk.
53:03So this is something that
53:05always happens.
53:06You set up your camera
53:07trap, you think you've
53:08got the right angle, and
53:09then one of the animals
53:09comes along and wants to
53:10change the angle, and
53:11oh, man.
53:13He's giving it a good
53:14ghost.
53:15I think it shows their
53:17playfulness.
53:18They come over to
53:18something new, curious,
53:19and then they come over
53:20and it's like, yeah, I
53:22think I'm going to play
53:23a little soccer with it.
53:24That's just great.
53:26Let's have a look at a
53:28couple of the other
53:28clips.
53:30Whoa.
53:32First clip.
53:33Exactly what we wanted.
53:34Wow.
53:35That's a big male, so I
53:37guess it's what we would
53:38expect this time of year,
53:39is these big guys are
53:40going to be the first ones
53:41coming out of the den.
53:43Females and the cubs are
53:43still up high.
53:44Casey, Casey, this is a
53:46huge bear.
53:49Well, remember when we
53:50set this camera trap, we
53:51were anticipating we'd get
53:52the whole bear, but he's
53:55bigger than that.
53:56He stands at two and a
53:58half meters tall.
54:00He's giving a real bear
54:02hug.
54:02That's a bear hug for
54:03sure.
54:05Wow.
54:05And there we go, doing
54:06that kind of cowboy walk
54:08you were talking about,
54:09right?
54:09Really trying to grind in
54:10a scent, leave those marks,
54:12that cowboy walk.
54:14That means one thing.
54:15I'm in town and I'm the
54:16boss.
54:17But what are they picking up
54:19and how do you think that
54:20affects their behavior?
54:22Well, I think as they
54:23emerge, it's the beginning
54:24of the mating season.
54:25So it's important for males
54:26to know if there's a bigger
54:27male around.
54:28It's like, oh, this big
54:30dude's here.
54:31Maybe I don't want to be
54:32here and they go the other
54:33way.
54:33And equally for the females,
54:35they want to know, you know,
54:37who's going to be the father
54:38of their next offspring.
54:39If there's any big tough guys
54:41around.
54:43Although the unusual weather
54:45a few weeks ago had brought
54:47some of them out of
54:48hibernation early, these males
54:50appear fighting fit.
54:55Spring is in the air and the
54:57bears are getting frisky.
55:04But they're not the only males
55:06getting boisterous.
55:09These elk are shedding
55:11their antlers.
55:12New ones will regrow
55:14over the next few months
55:15ready for the autumn
55:16rutting season.
55:20But perhaps the biggest
55:22male show-offs are down
55:24in the south.
55:25And Kate has a front row seat
55:28for their fabulous performance.
55:36It's mating season
55:38for the sage-grouse.
55:41And they really like to make
55:42a proper song and dance
55:44about it.
55:44That sound, it's really difficult to describe.
56:00It's like a sort of popping and a drumming.
56:03It's that combined with these wonderful, very showy, puffed up white chests and those fanned
56:14out black tail feathers that will attract the females.
56:19Oh, there's one.
56:20And they will literally do a fly pass.
56:24They'll sort of fly over and look down and go, oh yeah, no, I don't mind the look of that
56:27one.
56:27I'll give that one a go.
56:30Greater Yellowstone is a stronghold for the sage-grouse, a species under threat.
56:34Once numbering tens of millions, there are now just a few hundred thousand of these birds
56:40left.
56:41And many of them rely on Yellowstone, where there's still plenty of their habitat, sagebrush.
56:47It's now around 11 degrees, perfect for breeding.
56:56But success will depend on how the thaw progresses.
57:00Chicks won't do well if the temperatures soar too quickly.
57:09So far during the thaw, some of our animals have done well and some haven't.
57:13The jumping around in temperature at the end of winter confused some bears and made life
57:24difficult for the owls.
57:27One of the mildest winters on record and a lack of snow prevented the wolves hunting successfully.
57:34Yet the elk and bison emerged from the season in high numbers and with plenty of fighting spirit.
57:41Soon, this landscape will be transformed from brown and barren to lush and green.
57:50But the arrival of spring doesn't necessarily mean that life will get easier for our animal
57:55families.
57:56All those newborn youngsters will mean that there's lots of competition for food and the predators
58:01will be ever present on the lookout for the young and the vulnerable.
58:06Tomorrow night, will the grizzly bear cubs find enough food to eat when they venture out
58:11into the big wide world?
58:15We join a beaver family, but will they deal with the deluge?
58:20The water level is so much higher.
58:23After a difficult winter for the wolves, will their luck turn?
58:29There is a nest of great grey owl chicks, but will they all survive?
58:34Oh, he is struggling.
58:40As Kate said, that's tomorrow at the same time, nine o'clock.
58:44Well, it's new, it's outrageous, and some may say revolting.
58:48You'll certainly need to see it to believe it, a new series begins next, here on BBC Two.
58:53We'll see you next time.
58:54Bye.
58:55Bye.
58:56Bye.
58:57Bye.
58:58Bye.
58:59Bye.
59:00Bye.
59:02Bye.
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