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The Key to Studying a Blue Whale? Look At the Ear Wax

Update Date: Sep 17, 2013 11:01 AM EDT
Blue Whale
Researchers looked at the ear wax of a deceased 12-year-old blue whale and mapped out testosterone and cortisol levels as well as the content of pollutants. (Photo : Flickr/ mikebaird)

One of the most magnificent creatures in the world and arguably one of the hardest to study is the blue whale. These immense creatures spend the majority of their time in the deep waters of the ocean, giving human a few glimpses here and there when they come up for air. Even though these animals are hard to study, researchers have found the key to uncovering the chemical biography of a blue whale. According to researchers, studying the blue whale's ear wax can reveal a lot about what the animal has been through.

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"[Ear wax] looks like a long candlestick that's been beat up a bit," described Sascha Usenko from Baylor University according to the National Geographic. "It's not appealing-looking."

Even if the ear wax is not fun to look at, researchers might jump at the opportunity to study it. Unfortunately, the only time that researchers can get their hands on a blue whale's ear wax is after the whale has died. For researcher Stephen Trumble, he managed to get the ear wax of a 12-year-old blue whale that died from a collision with a large ship off the coast of California in 2007. Even though researchers have known that ear wax can reveal a whale's age based on the different colors of wax that represent times of feeding and migrating, the research team composed of Trumble and Usenko believed that more could be uncovered from a piece of ear wax.

Together, the research team was able to get an idea of the chemical biography of the whale. They found that during the first three years of the whale's life, his testosterone levels had risen. After the three year mark, the levels started to fall until he turned nine-years-old. At this stage in life, the testosterone levels jumped up 200 times. The researchers believed that that was the turning point when the whale had become sexually mature. This discovery was huge because previous research had estimated that a whale matures between five to 15-years-old, a range that is quite large.

Aside from testosterone levels, the research team also measured cortisol levels, which indicates the amount of stress the whale might have gone through. They found that levels of this hormone rose over the course of the whale's life. The levels did peak at around the same time testosterone levels rose. The researcher believed that stress increased due to the need to compete for mates with other male whales.

"I think about what I was like that age," commented Udenko. "A raging bull, trying to figure out my place in the social order...I was pretty stressed out."

From the ear wax, the researchers also discovered the presence of 16 pesticides, flame retardants and other pollutants. The researchers believe that the whale had inherited a majority of the pollutants from his mother because the pollutants were highly concentrated within the first six months of life. The team also found growing levels of mercury. Even though the ear wax method can reveal a lot about a whale's life, toxicologist John Wise from the University of Southern Maine remind people that ear wax only provides information on what was accumulated in the fat. This type of information cannot provide researchers with an understanding on how the pollutants actually affected the whale's health.

"Nevertheless, it's a new and useful part of our whale conservation toolbox as we seek to better understand ocean pollution," Wise added.

The study was published in the Proceedings of the National Academy of Sciences (PNAS)

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