(majestic music)

(water splashing)

- [narrator] Humpback whales.

These charismatic mammals

occur throughout
the world's oceans

(water spraying)

and they have long fascinated

those lucky enough
to observe them.

(camera shutter clicking)

(whales calling)

- [anke] They have this
really complex social system.

- [andy] They're quite
intelligent critters.

- [rachel] The whale
gives a feeling

of the wildness of the world.

(whale thumping)

(somber music)

- [narrator] Once nearly
hunted to extinction,

these awe-inspiring animals

have made a remarkable
comeback since 1966,

when the International
Whaling Commission

completed the global ban
on commercial whaling

of humpback whales.

- [martin] The North
Pacific humpbacks,

they were hunted quite heavily

down to about 5% of the
original population size.

- [andy] Some have estimated

that there was about
1,200 to 1,400 individuals

in the entire North Pacific.

- [marc] Humpback
whale populations

really were severely depleted,

and it wasn't until
they became protected

through acts like the
Marine Mammal Protection Act

and the Endangered Species Act

that we started to see a
recovery of these populations.

(cheerful music)

- [narrator] Since the 1970s,
researchers have been studying

the distinct humpback
whale population

that migrates between
feeding grounds

in southeast Alaska and
breeding grounds in Hawai i.

With time, the numbers of
animals steadily increased,

and in 2004, a multi-year
research effort

involving more than 50
research groups got underway

to determine the
abundance of humpbacks

throughout the North Pacific.

- [adam] It was estimated

that there was a little
over 10,000 whales

now visiting Hawai i.

Now from less than a
thousand in the 1970s

to over 10,000 in 2006,

and that was from a
population North Pacific wide

of about 21,000 whales.

That's an incredible
recovery story.

The rate of annual abundance
increase was about 6 to 7%.

(low urgent music)

- [narrator] Based on this
assessment and others,

the National Oceanic and
Atmospheric Administration

removed the Hawai i
distinct population segment

of humpback whales

from the U.S. endangered
species list in 2016.

- [lars] It's not very often

that we see these
conservation successes.

So that's an example of us
doing something right in nature.

(water spraying)

- [joe] So people are
breathing a sigh of relief

thinking they're
out of the woods.

- [narrator] But the celebration

of this incredible
conservation success story

was short-lived.

- [eden] In the 2015/2016
whale season here in Hawai i,

we started to get
anecdotal reports

that whale numbers
were lower than usual.

So initially we thought maybe
there's just a late arrival,

could be patchy distribution,
not really sure,

but that trend continued
for the next three seasons.

(camera shutter clicking)

- [andy] We started seeing
fewer whales here in Alaska,

far fewer calves than we
had seen in previous years,

we're seeing more
whales apparently that

and we're seeing a lot more
skinny and emaciated whales.

- [marc] It came as a big shock

because the humpback
whale population

had been recovering so steadily.

All of us really
were caught off guard

and we just didn't
know what to think.

- [adam] It was a major concern.

You can't help but be
impacted emotionally.

(water spraying)

(plane engine whirring)

- [joe] People
think of scientists

as being kind of all
head and no heart,

but no, it's quite different.

(fin thuds)

After you've been studying
the species for a while,

it becomes a
personal involvement.

- [adam] If they're missing,

it's like losing
a family member.

(water spraying)

- [eden] Cetaceans, you know,
whales, dolphins, porpoises,

are really canaries
in the coal mine.

(water spraying)

They tell us the
health of our oceans.

And so when they're
not doing that well,

we really need to listen.

(wistful music)

- [narrator] What had
happened to the humpbacks?

And how did the scientific
community mobilize

to answer this question?

(dramatic music)

- [announcer] Major
funding for this program

was provided by the
Batchelor Foundation,

encouraging people to
preserve and protect

America's underwater resources.

Additional funding was provided

by the Parrot Family Endowment
for Environmental Education.

(wistful music)

- [narrator] For decades,
scientists in southeast Alaska

and the main Hawaiian Islands

have been studying
the humpback whales

that frequent their waters.

(whale calling)

- [andy] The whales are in
Alaska

They definitely
start to drop off

in November through December

with a very low
point in January,

and then they start coming
back up in abundance

across the late winter
and early spring.

(camera shutter clicking)
(whimsical music)

- [narrator] The vast
majority of whales

that feed in southeast Alaska

will migrate thousands of miles
to the main Hawaiian Islands

to breed in late winter
and early spring.

- [andy] I think we estimate
now it's probably 88%.

What seems to drive the areas
that the animals travel to,

seems to be where they
went with their moms.

(gentle music)

If you were born in Hawai i

and your mom brings you up
to Alaska in your first year,

you're gonna come back to
Alaska and the odds are,

you're gonna go back
to Hawai i as well.

- [narrator] Experts
in both locations

are used to seeing many of the
same whales year after year.

So when the animals
stopped showing up

in their usual numbers,
people became concerned.

(regal music)

- [eden] In 2018, the Hawaiian
Islands

Humpback Whale National
Marine Sanctuary,

helped to convene
over 30 researchers

and I think it was
over 17 institutions,

to come together and try to
figure out what's going on

with our North Pacific
stock of humpback whales.

And so this involves people

from all the different islands
here in Hawai i and Alaska,

and we're really
trying to work together

to figure out what is going on.

(water spraying)

- [marc] It's very important, I
think,

to have these discussions
and these collaborations,

because we have a lot
of knowledge gaps.

- [joe] The consensus of the
meeting

was that we needed to,
you know, figure out,

you know, what their
status was now,

using different methods.

(regal music)

- (Sanctuary Employee)
Sighting!

9-2-0-9-2-3.

- [narrator] Researchers
at the Hawaiian Islands

Humpback Whale National
Marine Sanctuary

came up with a
three-pronged approach

to determine how many whales

are coming to the winter
breeding grounds each season.

- [eden] The hope is that if we
combine each one of these data

that we'll get a
better understanding

of how many animals are really
in our waters here in Maui.

(upbeat music)

(air hissing)

- [marc] We have a number
of acoustic recorders

out in various parts of
the Hawaiian Islands.

- [narrator] While on
the breeding grounds,

the male humpbacks
perform elaborate songs,

which become the dominant
source of sound underwater.

(whales calling)

- [marc] The acoustic recorders
help us determine

when whales are in
Hawaiian waters,

because the acoustic
energy increases,

so we can measure the
arrival of the whales

in the December timeframe.

The acoustic levels
go up rapidly.

They usually peak around
February or March,

and then decrease in
the April timeframe.

(thoughtful music)

Now, that allows us to track
the whale season itself,

but then we can also
use that information

to compare the whale
seasons between years.

- [narrator] The
scientists discovered

that between 2015 and 2018

the acoustic energy recorded
at six sites off Maui

dropped by 50% during
the peak whale season.

- [marc] Not only was the peak
of the chorusing was lower

during those three years,

but we could tell that
the season changed

and the whales started
to leave Hawaiian waters

earlier and earlier.

(boat engine whirring)

(majestic music)

- [narrator] Knowing this,
the experts decided to count

the actual numbers of
whales in the area.

Sanctuary staff began
regular boat surveys

in the leeward
waters off west Maui.

This is an area where whales
tend to occur in large numbers,

and it overlaps with
the coverage area

of the acoustic recorders.

- [eden] We conduct roughly
about 10 to 12 vessel

in a whale season.

- [narrator] Surveys
are scheduled

between December and
April of each year

to capture the beginning,
peak, and tail end

of the humpback whale
breeding season.

- [eden] Each
survey is a full day

and we follow a
systematic transect line.

- [narrator] While the
boat surveys are underway,

(low urgent music)

Ph.D. Candidate Anke
K gler counts whales

from an elevated shore station
overlooking the same area.

- [anke] So we try to schedule

the boat and land
days at the same time,

and I'm also doing
additional land surveys.

I come up here like once a week

and I scan the entire area for
any humpback whale presence

from about eight
o'clock to 2:30,

and then I do scans for
30 minutes every hour

and basically try to get the
location of every whale I see.

- [narrator] Once
Anke spots a whale,

she uses a surveyor's
instrument called a theodolite

to measure the horizontal
and vertical angle

of its position.

- [anke] And we can use those
angles

the actual GPS
position of the whale.

It gives us a spatial
distribution of the whales

at a given time in the area.

- [marc] By combining these
efforts,

is show that between
2015 and 2018,

there was approximately
a 50% decrease

in the number of whales
that were occupying

the area that we've
been monitoring.

- [narrator] In the three
years that followed,

the numbers of whales
generally increased again,

though scientists say there
were some fluctuations

in the lengths of the seasons.

- [anke] I've seen for example,

like shifts in the
peak of the season.

The numbers I'm seeing drop
like earlier in some years.

- [rachel] No, I think
there

Yeah, there was, yeah.

So just head down
towards that way.

- [rachel] Fine.
- Yeah.

- [narrator] Researchers with
the Keiki Kohola Project,

who focus on mothers and calves,

also recorded a drastic
decline in whale numbers

over a three-year period.

(thoughtful music)

- [rachel] Our long-term study
is a transect-based study,

which encompasses
one of the main areas

that's favored by
mother and calf pairs

when they're in Hawai i, and
that's been underway since 2008

and we do it three
times a season.

Mid-January, mid-February,
and mid-March surveys.

2016 is when we first saw
a really clear decline

in the numbers of whales we
were seeing in Hawaiian waters,

and then over the next
two years that played out.

When we compared 2013
and 14 to 2017 and 18,

those two-year periods, we
were seeing a 76% decrease

in the numbers of
mothers and calves

that we encountered on
those transect lines.

Related to that,

we also started to see
a change in seasonality.

2019 was when we first saw
our numbers coming back up

quite healthily in Hawai i

and we were getting back
to maybe where we were

at the start of the demise.

(plane engine whirring)

- [narrator] Another
team of experts

saw similar improvements

when in 2019 and 2020, they
conducted aerial surveys

to estimate the whales' density.

(gentle music)
(radio chattering)

This group focused its efforts

on the entire Maui Nui region,

where humpbacks are
known to aggregate

in the relatively shallow water.

- [joe] The highest
densities of humpbacks

are here between
those four islands.

- [adam] What we've been doing
is three aerial surveys,

one prior to the peak of
the season, one at the peak,

and one post peak.

(radio chattering)

- [narrator] The scientists
used the same survey methods

as they did during
aerial surveys

conducted between 1993 and 2003

to ensure that results
would be comparable.

At that time, they discovered
that the whale population

was increasing at an
average rate of 7% per year.

The 2019 and 2020 surveys,
which covered a smaller area,

didn't show the same
annual increase,

but the findings suggest that
the population of humpbacks

that winter in Hawai i appears
to be relatively stable.

- [joe] That's one of the most
promising statistics

that we picked up in 2019.

There's 9% of the pods
that we saw had calves

and that's higher than
it had been in the past.

(thoughtful music)

(radio beeping)

- [narrator] Like all
their colleagues in Hawai i,

a network of research
partners in southeast Alaska

observed similar trends.

- [andy] We were finding far
fewer animals in 2016, 2017, and

than we had in previous years,

we're seeing record
low numbers of calves,

and we're were
finding a large number

of skinny and emaciated whales.

- [john] By the time 2019 came
around,

things were looking
a little bit better.

We started seeing calves again,

the whales seemed a little
bit healthier, looked fatter,

and we saw numbers
increase in the southeast.

In the Prince William Sound,

the numbers have not
quite bounced back yet,

we're still seeing
really low, low numbers.

- [martin] Glacier Bay National
Park,

they have this incredible data
set dating back 30 plus years

of the same
individuals coming back

with incredibly high
consistent site fidelity.

And unfortunately, some of
their main animals just vanished

and they still have
not come back there.

- [narrator] So what had
happened to the whales

during that three-year period?

- [adam] There seemed to be
three different phenomenon

that were converging
at the same time.

One was a strong El Nino and
that's a normal phenomenon

that sometimes
occurs, of course.

- [narrator] In addition,
a shift occurred

in the Pacific
Decadal Oscillation,

a longer-lived pattern
of climate variability.

- [adam] Which is also a normal
kind of warming event,

but on a longer-term scale.

- [narrator] These
two warming events

coincided with the
worst marine heatwave

ever recorded in
the North Pacific.

- [rachel] And that created
a lens of warm water

that became known as the blob,

mainly because it
crept very slowly

and expanded across the
waters of the North Pacific.

- [martin] Putting them all
together,

- [rachel] At that point, you
had three levels of warming

that were all going
to amplify each other.

And once those waters are warm,

the problem is that they don't
turn over at the same rate,

and so nutrients don't
cycle through the water.

- [marc] Which then, of
course, effect the life

that depends on those nutrients.

- [john] It will change the
composition of the plankton.

A lot more warm water
species can show up.

They don't have as
much fat in them,

so that in turn
means less fatty food

for things like
krill and herring,

which makes it harder for
those those animals to make it.

- [narrator] In essence, the
food the whales depend on

while in Alaska had
been drastically reduced

in the areas they're
known to frequent.

- [john] They're
feeding on krill,

little shrimp-like creature

that get really
dense aggregations,

and, small schooling fish.

So things like herring,
capelin, sand lance,

sometimes they eat
juvenile salmon.

So it's, fish and
krill is the main diet.

- [marc] The first year that we
noticed these changes,

there were an unusually
high number of reports

of dead whales, both here in
Hawai i, but also in Alaska,

but we didn't think
that it was enough

to explain the decrease
in whale numbers.

- [martin] These whales follow
food.

So if we're seeing less
sightings of animals

in areas that are
really well-researched,

there's a good chance

that these whales have
been moved elsewhere.

They could be utilizing offshore
areas a little bit more.

There's certainly far
less research effort

out in these rough open waters.

- [marc] And during the
breeding season,

it could well be that a
certain number of whales

just didn't have enough fuel
in their tank, so to speak,

to make the migration
to the breeding grounds,

and so it would be
a wasted effort.

- [narrator] Scientists
say it's also possible

that some of the whales migrated

to one of the other
known feeding grounds

in the North Pacific,

or possibly went to the
northwestern Hawaiian Islands

where there is no monitoring.

- [martin] As the climate
changes, a

that these sorts of events
are becoming more frequent,

and if this was a reaction
to this sort of event,

now what happens when
this becomes the norm?

- [adam] I think that this
really

or the tip of the iceberg.

- [narrator] Knowing the impact
the severe marine heatwave

had on the whales made
scientists want to learn more

about the animals' health
and body condition,

and how that changes
over the course of a year

as well as between years.

- [martin] Unfortunately, we
still

what a healthy humpback
whale looks like.

So for us to be
able to figure out

when a population is impacted,

we need to know what
the baseline is.

(water spraying)

(low urgent music)

- [narrator] To do so,

scientists from the Marine
Mammal Research Program

at the University
of Hawai i at Manoa

are collaborating closely
with other experts

in Hawai i and Alaska.

Ph.D. student Martin van Aswegen

spends each April through
October in southeast Alaska

conducting research with
the Alaska Whale Foundation.

- [andy] We're studying the
distribution of the animals,

the abundance of the animals,

looking at the numbers of
calves they're producing,

and how that changes
across the season.

(drone whirring)

- [martin] Three, two, one.

- [narrator] In addition,
Martin is collecting

regular measurements of
the animals from the air.

- [martin] We're using these
drones to noninvasively

get over the top of the
whales as they're surfacing.

And as they surface,
we can get a video,

a high-resolution image
of their body contours

so we can see how
long the whale is,

but also how wide the animal is,

and using some
software that we have,

we can measure the total
length of the animal,

as well as the width,

across 20 different
points on the body.

We can do this again
and again and again,

with the same animals
and different animals,

and this allows us
to see how quickly

these whales are gaining mass.

Their job up here is
essentially just to gain

as much mass and
weight as they can

in preparation for when
they start to migrate south

when they're fasting.

- [lars] So we're trying
to estimate how much

they need to feed up in their
foraging grounds, so Alaska,

and what is the cost of the
migration down here to Hawai i?

- [martin] In addition to
our

we're sampling in
Hawaii as well.

We're sampling January,
February, March.

Some of the measurements
that we're getting

are quite surprising,
things like adults losing

up to 28 inches of
their body width

while on the breeding
grounds, for example,

and that's without a calf,

that's just a
regular mature adult.

- [narrator] Between
2018 and 2021,

Martin captured approximately
4,100 measurements

of over 3,200 humpbacks
in Hawai i and Alaska.

This includes repeat sightings

of more than 80 individual
animals in both locations

within six months of each other.

- [andy] The way you recognize
an individual whale

is by looking at the underside
of its tail, its fluke.

Every whale has unique black
and white pigmentation patterns

and the shape of the
trailing edge of the fluke.

(low urgent music)

- [narrator] Whale
experts from all over

have long used
photographs of the flukes

as a way to identify

the individual animals
they're studying.

New technology has
revolutionized this

- [lars] Very recently,
a research group

has started an initiative
called Happy Whale,

which is a software that allows

automatic detection and
matching of fluke shots,

which is very time-consuming
with with the naked eye.

- [narrator] Now whale
researchers everywhere

can not only upload their images

for faster identification
within their database,

but they're also able to see
if any of their colleagues

have seen the same
whale elsewhere.

(water splashing)

- [lars] This new Happy Whale
initiative is really helpful

for all of us as a
research community

to try to understand
the movement patterns

(water spraying)
(gentle music)

- [narrator] In addition,
the scientists collect

small tissue biopsies of some
of the whales they measure.

This allows them to
study the animals' diet,

look at their fat stores,

and determine if
females are pregnant.

- [lars] The biopsy
samples also tell us

about different stress levels
in these animals as well.

- [adam] As a whale is fasting
and losing its body mass,

it should be increasing
in its stress levels.

This part was.

What we're interested in

is kind of measuring
a baseline for that,

so that when climate
events occur,

we have something
to compare it with.

(regal music)

- [martin] Coming up.

Take off.

(drone whirring)

One o'clock.

- [narrator] Whale experts
in Alaska and Hawai i

are relieved to see that the
humpbacks seem to be recovering

from the impacts of the
recent marine heatwave.

But, they say, they
are also keenly aware

that they need to be
prepared for the future.

- [andy] People who study
these warm water events

predict that they're gonna
happen more frequently

and they're gonna be more
persistent and last for longer

moving forward as a
result of climate change,

and so that gives
us a lot of concern

that what we saw in those
years, 2016 to 2018,

will almost certainly
happen again.

- [adam] It makes us aware of
being

and how we need to really
use these different tools

that we're using right now

to continue to monitor
the population.

And collectively being able to
monitor not just the whales,

but the environmental
factors as well

is going to be critical.

(regal music)

(whale calling)

(inspiring music)

(water rushing)

(drone whirring)

(water spraying)

- [announcer] Major
funding for this program

was provided by The
Batchelor Foundation,

encouraging people to
preserve and protect

America's underwater resources.

Additional funding was provided

by the Parrot Family Endowment
for Environmental Education.

(upbeat music)