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Do Whales Keep their Secrets in Ear Wax?

Don’t believe it, the whales keep their secrets in their earwax

After testing and analysis, they determined that the blue whale began to become sexually mature at the age of 9, because the level of male hormones in the earwax increased 200 times from the 9th year.


Cetaceans are very large and live for a long time. As mammals, they do not possess dexterous hands like humans, and their forelimbs have been specialized in fin-shaped. These three characteristics determine that a whale will accumulate a lot of earwax in its lifetime.


Earwax of Blue Whales

Similar to us, the formation of cetacean earwax is also caused by glands secreting oily secretions, which accumulate foreign bodies that eventually harden into cones. The largest blue whales have earwax up to 25 cm long and look like goat horns or disgusting candles. 

The earwax of fin whales is tougher than that of blue whales, while bowhead whales are softer and almost liquid, and sei whales are black and brittle. Regardless of the geometry of their earwax, these disgusting secretions hide a huge amount of information.


Can earwax be regarded as a chemical biography of cetaceans?

Generally speaking, cetaceans eat a lot in summer, and when migrating in winter, their earwax will show changes in depth. By cutting their tapered earwax strips, you can find that there are alternating bands like tree rings inside. 

We can count these banded changes to estimate the age of the whale. It can even analyze the material intake in the cetaceans when each belt layer is formed. Earwax can be regarded as a chemical biography of cetaceans.


Stephen Trumble and Sascha Usenko from Baylor University have worked out how to interpret this information in whale earwax. They proposed that whale earwax not only reveals the life course of whales, but also reflects the marine history of the time they lived. Including hunting threats, temperature changes, and pollutant conditions can all be understood here. 

Trumble and Usenko believe that even if all records of whaling are now erased, they can still reconstruct the historical changes in the scale of whaling through the level of stress hormones in the earwax.


Initially, the two verified their conjecture through a blue whale that had died outside. It was a 12-year-old male blue whale who was hit and killed by a ship off the coast of Santa Barbara in 2007. 

After testing and analysis, they determined that the blue whale began to become sexually mature at the age of 9, because the level of male hormones in the earwax increased 200 times from the 9th year. 

In addition, they also found that one year before the start of sexual maturity, the male blue whale had the highest levels of stress hormones, which may be a sign of the individual's physical and mental changes. 

Traces of pesticides and flame retardants were also found in the earwax, mainly in the first six months after birth. It is speculated that it may be ingested from breast milk. 

"I was surprised by the application of this technology, not only for persistent chemicals, but also for many easily degradable hormones," Usenko said.


Whale and earwax

This is just the earwax of a whale. It is easy for us to collect more earwax samples through appropriate museums. "Museums have always been proud of collecting everything they get, waiting for scientific progress to come in handy," Trumble said. "We contacted Charles Porter at the Smithsonian Institution and he said, 'I am very interested because we have some samples of whale earwax and were considering whether to throw them away.' Now these samples can become the protagonist instead of being Throw it away."


Trumble, Usenko and colleagues finally measured cortisol (a stress hormone) levels in the earwax of a total of 20 blue whales, fin whales, and humpback whales. The oldest sample is from a whale born in 1871. 

The small team measured the changes in this stress hormone during the life cycle of each individual, using the lowest level in earwax as a reference. 

They compiled these data into a 146-year-long whale pressure chronology, and compared it with the whaling data of the 20th century. "When we saw the comparison between the two sets of data, it felt like ‘really?!’" Trumble said.


The degree of match between the two sets of data is amazing. In the early 1960s, when whaling reached its peak, cortisol levels in whale earwax were also the highest. Subsequently, whaling activities were gradually banned, the amount of whaling fell by 7.5% per year, and the level of cortisol in earwax decreased by 6.4% per year.


To some extent, this is not strange. When cetaceans face the situation of being hunted, their pressure will naturally increase. 

However, the degree of matching is surprising. The data of these 20 whale earwaxes basically restores the history of global whaling.


However, there are still some periods where the data is different. For example, during World War II, although whaling activities were greatly reduced, their cortisol levels increased by 10%. 

Although there are few harpoon guns in the ocean, it is full of battleship submarines, depth bombs, and torpedoes. These noises cause whales to feel no less nervous than whaling ships, which is also a great pain in whale life today.


Since the 1970s, whaling opportunities in the northern hemisphere have been reduced to a negligible level, but the cortisol level of cetaceans has not decreased as expected, initially rising slowly, and then suddenly increasing. Trumble and Usenko believe that this phenomenon may be related to the abnormal increase in ocean temperature.


In this 146-year chronology, whale cortisol levels have soared in the early 21st century, almost reaching the highest level in history. This may be because the blue whale in their study was the only individual that survived the whaling era, and it has been under extreme stress. 

Could it be that it was frightened by the ships sailing in the sea area? 

Could it be that it became sick because of ingestion of pollutants such as mercury and pesticides? 

We don't know, but its cortisol has remained at a very high level since the whaling era. "When I saw it, I thought: this is an individual under stress, as if it is being hunted," Usenko said.


"I think this will completely change our research on whale biology," said Kathleen Hunt from Northern Arizona University, but he was not involved in this work. "Biologists who study cetaceans are used to collecting tiny information in samples, such as a single fat biopsy, one or two stool samples, or some photos scattered for many years. A piece of earwax is more like a continuous 200 samples, every 6 They are collected from the same animal once a month." They are like ice cores used by climate scientists to return to Earth’s distant past.


Earwax strips are especially meaningful for long-lived creatures like whales. They may take ten years to mature sexually, pregnancy may exceed one year, and it may take longer to recover from traumatic events. 

"We have never really had a way to track the stress response of individual whales on various time scales, so this is very exciting," Hunt said.

Now, the team is studying the progesterone in earwax and analyzing chemical isotopes and other indicator molecules in the whale’s diet. "We got a lot of data from these earwax, and these data are only our preliminary," Trumble said. They haven't studied all the samples. “The Canadian Museum of Nature in Ottawa has 4,000 earwax strips, and 100 of them have already been shipped to us. Our research will go deeper.”

Author: Naval Kishore

Education: Masters Degree in Actuary

The author is an Actuarial expert with 20 Years of Work experience in Fisheries work


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