From the most northerly part of Alaska comes a warning message.
The majestic snowy owl is disappearing
and with it, the lemming a keystone species.
What is happening in the Arctic tundra?
High above the Arctic
Circle, scientists come hunting for data.
Since 1992, they've been monitoring the predator-prey relationship
between the snowy owl and the brown lemming - the owls
primary food source.
They've discovered that the health of snowy owl populations
is entirely reliant on the dramatic boom-and-bust reproduction
cycles of the little rodent,
the boom used to happen here every three to five years.
Now it's unpredictable.
The cycle has been disrupted, and in North America,
the snowy owl population has dropped by 64%.
Mature, experienced owls
can live here year round alongside the polar bears.
Even in the constant twilight, their telescopic
vision and acute hearing ensure hunting success.
But there's not a lot of prey at this time of year.
Not enough to feed a family.
So breeding is completely dependent on the lemmings.
And the little rodents won't appear until May,
when melting ice reveals their burrows.
For now,
the lemmings are hidden from the eyes of the snowy owl,
traversing their tunnels, eating moss and shoots ...
and breeding.
The owls know when the lemmings are around.
Scientists just aren't sure how.
When the days lengthened, the Arctic tundra comes to life.
The Sun won't set from mid-May to early August.
1700 species of plants thrive here in the summer, but it's too cold
for trees to grow, which means the owls must nest in the open.
The only place in the U.S.
where snowy owls regularly breed is here in the region around Utqiagvik.
How many will arrive this season?
A female has found a nesting site.
She'll lay between five and seven eggs.
She's chosen a mound formed by the repeated
melting and freezing of the earth.
Even just a small elevation has advantages
above the boggy marshes, with a breeze that keeps the biting insects at bay
and a clear view in all directions to see approaching predators.
Snowy owls are nomadic.
They won't nest until they know lemmings are available in the area.
If lemmings are plentiful, lots of owls will nest
and lay up to 14 eggs in one clutch.
There's only one active nest on this stretch of tundra.
A sign that lemming numbers may be low this year.
In May, the lemmings
come out to feast on the defrosted vegetation.
They can consume up to eight times their own body weight in one day.
When there's a lemming population explosion, their impact on the Arctic
vegetation is so extreme that it's visible to satellites.
The lack of vegetation can even cause an increase in CO2 levels.
But the plants bounce back even
healthier once the lemming population crashes.
To stay safe from predators, the rodents forage near their burrows.
A snowy owl can spot a lemming from nearly
a kilometre away.
On silent wings,
this male swoops down to snatch the little rodent in his talons.
A perfect display of the "wallop" hunting method.
But the Hunter won't eat his kill.
After 32 days of incubation, his chicks have hatched,
the male must now provide them with all the lemmings they can eat.
An adult owl needs three to
five lemmings a day, but chicks have much greater demands.
They need to grow up fast.
In just three months, the young Owls must hatch, put on weight, disperse,
learn to fly and become independent all before it snows again.
From the day an owlet hatches until it becomes self-reliant.
It can consume more than 150 full grown lemmings.
But first, the lemmings have to be shredded into small baby beak
sized pieces.
Most other owl species hunt by night in the land of the Midnight Sun.
Snowy owls have no choice but to be active in the daylight.
The payoff is that they can hunt 24 hours a day.
But that won't be necessary for this male.
He's found an area where lemmings are abundant.
He brings them in like a fast food delivery service.
When the owlets start
swallowing whole lemmings in one gulp, the pressure to hunt increases.
The fates of the snowy owl are entwined with the lives
and deaths of these unassuming little rodents.
By the time the owlets are ready to fly,
they've eaten so many lemmings that they can barely face having another.
But thanks to the rodents, these juvenile owls will soon be leaving
the Alaskan Arctic for milder winter temperatures below
the Arctic Circle.
Unfortunately, there is no way that the amount of lemmings
this season could have sustained widespread breeding.
In this part of Alaska, the decline of both snowy owls
and lemmings began just over a decade ago.
Scientists don't yet understand the reasons behind the decline.
Is it linked to climate change?
Since their study here began, temperatures have risen.
Snow and ice cover have decreased and the vegetation continues to change.
Lemmings need snow for protection and rely on grasses
and other endemic tundra plants for nesting and reproduction.
And owls need lemmings.
If the lemmings disappear, the whole Arctic system will collapse
because these little rodents are a keystone species.
Many predators rely on them to survive.
And so lemmings may be the best indicator of environmental change.
But here's the thing.
Most of us don't take much notice of small rodents.
It may be up to the majestic snowy owl
to carry the warning message from their world to ours.
We have many more fascinating rodents
for you if you want to learn about all kinds of these underestimated
little animals, why not check out our gnawed playlist?