Whales’ earwax can unfold many secrets on its lifetime, marine pollution

The whales’ earwax, that is nearly foot-long and inch-thick tube, can unveil many secrets happening inside the water world.

According to the scientists, wax inside a whale’s ear stores all sorts of useful information on the animal’s exposure to pollutants and stress levels throughout life.

The team, led by Sascha Usenko, a environmental scientist at Baylor University in Waco, Texas, extracted an earplug from a blue whale, killed in a collision with a ship off the coast of Santa Barbara in California in 2007, and found it had come into contact with several organic pollutants and contained high levels of the stress hormone cortisol as it reached sexual maturity.

“It’s difficult to recover time-specific information on chemical exposure for almost any animal,” says Stephen Trumble, a biologist also at Baylor and a co-author of the study.


Interestingly, whales don’t hear as humans do. The fat deposits in their jaw direct low-frequency sound vibrations toward their eardrum, so the wax does not get in the way of their hearing.

With the passing time in the blue whale’s lifetime, the wax forms a solid, permanent tube. Researchers refer it to as an earplug. For scientists the earwax provides “unprecedented lifetime profile” of the largest mammal.

Researchers say, like tree rings, layers found within whale earplugs are used to estimate the animal’s age. Similarly, these wax can also help the researchers in finding the chemical pollutants that are responsible of extinction of blue whales and other oceanic members.

The team performed numerous chemical analyses to produce a profile of the whale’s life, researchers said. Within the wax, they found markers of the stress hormone cortisol, growth-inducing testosterone, contaminants such as pesticides and flame retardants, and mercury.

The study was published in Proceedings of the National Academy of Sciences.