In earwax, the tale of a whale
Researchers have reconstructed the lifespan of a male blue whale, including its brushes with both environmental pollutants and female blue whales, using its earwax.
Whales have earwax, and it's useful.Skip to next paragraph
In Pictures 24 bizarre creatures of the deep
Subscribe Today to the Monitor
Researchers have reconstructed the lifespan of a male blue whale, including its brushes with both environmental pollutants and female blue whales, using the lipids and waxes that plug its ear canal. The new technique gives marine researchers another tool with which to portrait a whale’s lifetime, allowing scientists to chronicle which hormones the mammal released and which chemicals it absorbed – and when it did so.
“This type of data is really, really rare,” says Sascha Usenko, a professor at Baylor University and a co-author on the paper, published in the journal Proceedings of the National Academy of Sciences. “This is a new opportunity to ask a lot more questions.”
RECOMMENDED: Are you scientifically literate? Take our quiz
Blue whales are big. To be exact about it, the blue whale, at up to 100 feet long and 300,000 pounds,is the biggest animal ever to grace this planet. Charmingly, their hearts are proportional: a blue whale’s heart weighs about 1,300 lbs. Their brains, though, are not, at just 16 lbs.
To get to this size (brain not included), blue whale calves need to grow about 250 lbs each day, or 10 lbs an hour, which requires a daily helping of about 500 gallons of its mother’s milk. At full size, the blue whale must eat about four tons of krill (a shrimp-like animal, but saltier-tasting), per day, to sustain its tremendous bulk. Since the blue whale is toothless, its mouth is instead fringed with lots and lots of baleen, a keratin-based bristle, which separates the krill from the water when the whale takes an ocean gulp, pushing the water out and the millions and millions of unfortunate crustaceans in.
But for all that is known about the long, big lives of blue whales, which live to be around 80 to 90-years-old, more is still unknown. While it has long been thought that whales feel the effects of human activities, including waste dumping and noise pollution, the biographies so far collected from whales have been isolated chapters, told in samples of the animal’s blood, feces, and blubber. Little is also known about the whale’s hormone levels during its development.
The idea of using earwax to fill in those knowledge gaps arose out of two facts, says Dr. Usenko. The first was that most baleen whales, from birth to death, accumulate layers of what is known as cerumen, better known to us as earwax, in their ear canal. That earwax is composed of alternating light and dark-colored layers, which are associated with periods of food bounty and austerity. Much as a fish’s ear bones record a tale of summer and winter feeding that can be used to confirm its age, the waxy layers provide an estimate of the mammal’s age, which each layer translating to about 6 months of time, based on whale migration patterns.
The second fact was that fat is a reliable repository of hormones and contaminants; at the moment, whale blubber samples are sometimes used to gauge which chemicals the animal has absorbed. And since earwax is lipid-rich, it too would be packed with the pollutants to which the animal had been exposed and the hormones it had pumped throughout its bloodstream.