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Forget Q-tips. The flimsy tools wouldn鈥檛 make a dent in the inches of earwax that build up over the eight or nine decades that a blue whale swims the oceans. Now, researchers have used the crud to reconstruct the life of one behemoths, unlocking the secrets of the pollutants it encountered and the hormones it releases鈥攁nd when.
The monstrous mammal is the largest living animal today, stretching up to 88 feet long and weighing 380,000 pounds. It dives to depths of 1,640 feet in search of krill鈥攖he small crustaceans that it largely subsist on鈥攎aking the whale incredibly difficult to study.
In an 鈥渁h-ha鈥 moment, Baylor University scientists hypothesized that earwax could help shed light more light on the blue whale, for a couple of reasons. The earplug is made up of wax and lipids, which trap hormones produced by the whale and chemicals it鈥檚 exposed to in its environment. In addition, the earplug records time, similar to tree rings: Bands of wax are laid down in roughly six-month intervals. (Blubber also traps chemicals, but there鈥檚 no way of knowing when a whale picked them up.)
By analyzing earwax, scientists figured they could determine when chemicals were absorbed or when stress levels peaked.
To find out if they were correct, in what might have seemed an odd request, they requested a sample from the Santa Barbara Museum of Natural History. The museum provided them with a nine-inch-long candle-like earplug from a 12-year-old 68-foot-long blue whale that died in a 2007 ship collision.
They discovered that the whale鈥檚 testosterone level peaked when he was ten years old鈥攃onfirming previous estimates of the male blue whale鈥檚 age of sexual maturity. Additionally, concentrations of cortisol, a stress hormone, increased significantly in the next year. The finding suggests that the spike indicated that he was competing with other males for a mate, write the authors in the , published in Proceedings of the National Academy of Sciences last month.
The earwax also contained pollutants such as pesticides, flame retardants, and mercury. The concentrations of these chemicals were highest during the whale鈥檚 first six months of life, suggesting they were passed on from his mother during nursing. Additionally, the color of the wax alternated between light and dark colors. The wax was a lighter color when the whale went through a period of abundant feeding because of a diet rich in lipids, while a darker color indicated he was migrating.
While the researchers only looked at one whale, it seems there鈥檚 an abundance of earwax. 鈥淥ne of the most profound advantages offered by earplugs is the ability to retrospectively examine critical issues through the analysis of archived museum samples, some of which were harvested in the 1950s,鈥 the authors write. That鈥檚 a lot of whale tales waiting to be told.