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Whale Ear Wax Reveals Environmental Pollutants

Some whales build up waxes, lipids and keratin into earplugs that tell researchers about a whale's lifetime exposure to pollution. Cynthia Graber reports

Cerumen. It’s a lovely word. Especially considering that it means earwax. And we’re not the only species that produces the stuff. Some whales build up waxes, along with lipids and keratin protein into what’s called earplugs. And researchers now know that examining these plugs tells them about a whale’s lifetime exposure to pollution.

Alternating layers of dark and light in the plugs correlate to seasons of feeding or migration. So the plugs have been used to determine a whale’s age. Think tree rings. 

In the latest study, scientists analyzed an earplug from an endangered blue whale killed by a ship near California. They found that levels of stress hormones doubled over the whale’s life.

They also found evidence that the whale had been exposed to pesticides such as DDT, with the highest levels during the whale’s first six months of life. The whale was likely exposed to the pesticides in its mother’s milk.

They also found a couple of peaks of exposure to mercury. The study is in the Proceedings of the National Academy of Sciences. [Stephen J. Trumble et al., Blue whale earplug reveals lifetime contaminant exposure and hormone profiles]

Future earplugs should offer additional clues about whale lives. So look for researchers to give new attention to leviathan cerumen.

—Cynthia Graber

[The above text is a transcript of this podcast.]

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