[OANNES Foro] The History of the Oceans Is Locked in Whale Earwax

Dom Nov 25 09:36:01 PST 2018

The massive plugs contain spikes and dips of stress hormones that perfectly
match the history of modern whaling.

The History of the Oceans Is Locked in Whale Earwax

 <https://www.theatlantic.com/author/ed-yong/> ED YONG

NOV 21, 2018

https://www.theatlantic.com/science/archive/2018/11/astonishing-history-lock
ed-whale-earwax/576349/

A humpback whale jumps out of the ocean

Whales are big, whales are long-lived, and whales have paddle-shaped
flippers instead of dexterous hands. These three traits inexorably lead to a
fourth: Over time, whales accumulate a lot of earwax.

Whale earwax forms like yours does: A gland secretes oily gunk into the ear
canal, which hardens and accumulates into a solid, tapering plug. In the
largest whales, like blues, a plug can grow up to 10 inches long, and looks
like a cross between a goat's horn and the world's nastiest candle. Fin
whale wax is firmer than blue whale wax, bowhead whale wax is softer and
almost liquid, and sei whale wax is dark and brittle. But regardless of size
or texture, these plugs are all surprisingly informative.

As whales go through their annual cycles of summer binge-eating and winter
migrations, the wax in their ears changes from light to dark. These changes
manifest as alternating bands, which you can see if you slice through the
plugs. Much as with tree rings, you can count the bands to estimate a
whale's age. And you can also analyze them to measure the substances that
were coursing through the whale's body when each band was formed. A whale's
earwax, then, is a chronological chemical biography.

 <https://www.baylor.edu/biology/index.php?id=68808> Stephen Trumble and
<https://www.baylor.edu/environmentalscience/index.php?id=954203> Sascha
Usenko from Baylor University have worked out how to read those biographies.
<https://www.nature.com/articles/s41467-018-07044-w> And they've shown that
whale earwax not only reveals the lives of their owners, but the history of
the oceans. Hunting, abnormal temperatures, pollutants-it's all there. If
all of humanity's archives were to disappear, Trumble and Usenko could still
reconstruct a pretty decent record of whaling intensity by measuring the
stress hormones in the earwax of a few dozen whales.

The duo first tested their idea of studying earwax by
<http://www.pnas.org/content/110/42/16922> analyzing the plug from a single
blue whale-a 12-year-old male that was fatally struck by a ship off the
coast of Santa Barbara in 2007. They could tell that the whale became
sexually mature when it was 9 years old, as that's when testosterone levels
in the plug shot up by 200 times. They showed that the stress hormone
cortisol peaked a year before that, perhaps a sign of the creature's
changing body and mind. They found traces of pesticides and flame retardants
that were especially concentrated in the whale's first six months of life,
and had likely been passed down in its mother's milk. "I was surprised at
how well [the technique] worked, not only for persistent chemicals but for
hormones that typically rapidly degrade," Usenko
<https://www.nationalgeographic.com/science/phenomena/2013/09/16/biography-o
f-a-blue-whale-told-through-ear-wax/> told me at the time.

That was just one earwax plug, but it was surprisingly easy to get more.
They just had to call curators at the right natural-history museums.
"Museums are notorious for collecting everything, and waiting for the
science to catch up," Trumble says. "We called
<http://vertebrates.si.edu/mammals/mammals_staff_pages/potter_charles.cfm>
Charles Potter at the Smithsonian Institution, and he said, 'It's
interesting you called because we have pallets and pallets of these ear
plugs sitting around, and we're thinking of throwing them away.' Instead of
being thrown away, those ear plugs are now objects of wonder."

Trumble, Usenko, and their colleagues ended up measuring cortisol levels in
the plugs from 20 blue, fin, and humpback whales, the oldest of which had
been born in 1871. The team measured how this stress hormone varied over the
lifetime of each animal, relative to the lowest levels found in each plug.
They then combined these readings into a 146-year chronicle of whale stress,
which they compared to a record of all whaling data from the 20th century.
"We plotted the two together, and were like: 'You've got to be kidding me,'"
says Trumble.

The two data sets matched beautifully. When whaling increased, cortisol
levels rose, hitting their peak during the heyday of whaling in the early
1960s. After moratoriums were adopted in the 1970s, whaling harvests fell by
7.5 percent a year and cortisol levels in earwax fell by 6.4 percent a year.

To an extent, that's not surprising: Of course, whales would be more
stressed if their pod-mates are being harvested. Still, it's astonishing
just how well the two data sets match. Trumble and Usenko could get a pretty
good picture of global whaling efforts through the lived experiences of 20
whales.

There are a few discrepancies, and they're telling. For example, whaling
fell away during World War II while cortisol levels rose by 10 percent. The
oceans may have been relatively free of harpoons, but they were instead
filled with battleships, submarines, depth charges, and the sounds of
warfare. Those indirect disturbances, it seems, were just as stressful to
the whales as their hunters had been-and they continue today.

Since the 1970s, whaling has dwindled to negligible levels in the Northern
Hemisphere, but if anything, cortisol levels have risen-slowly at first, and
then more dramatically in recent decades. Trumble and Usenko showed that
this rise correlates with the number of days when ocean temperatures were
unusually high.

The team's 146-year chronicle also has a gigantic spike in the early 2000s
when cortisol levels seem to shoot through the roof. That's because of the
very first blue whale they studied. It was the only individual whose life
spanned those particular years, and for whatever reason, it spent those
years in an extreme state of stress. Was it reacting to the noisy shipping
lanes that crisscross California's waters? Was it suffering from the
mercury, pesticides, and other pollutants in its body? No one knows, but its
cortisol was hitting highs that haven't been seen since the days when people
killed whales in the hundreds of thousands. "When I look at that, I think:
Here's an individual that's under stress levels as if it's being whaled,"
says Usenko.

"I think this is going to revolutionize our studies of whale biology," says
Kathleen Hunt from Northern Arizona University, who was not involved in the
work. "Whale biologists are used to gleaning tiny bits of information from
samples like a single blubber biopsy, one or two fecal samples, or a few
photographs scattered over years. An earwax plug is more like 200 samples in
a row, taken from the same animal, every 6 months, for its whole life."
They're like the ice cores that climate scientists use to peer back into the
Earth's distant past.

The plugs are especially informative because whales are so long-lived. They
can take a decade to mature, go for years between pregnancies, and spend
much longer recovering from episodes of trauma. "We've never really had a
way to track individual whale stress responses over those sorts of timescale
before, and it's very exciting," says Hunt.

The team is now examining the wax for pregnancy hormones, chemical isotopes
that reflect the whales' diet, and other telltale molecules. "We're getting
tons and tons of data from these earplugs that we've only ever assumed,"
Trumble says. And he's not running out of material to work with. "The
Canadian Museum of Nature in Ottawa has 4,000 ear plugs, and we had 100
shipped to us. We're getting quite deep into this."

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