Human history preserved in whale earwax

Scientists are measuring stress in whales – using the animal’s earwax. The research is uncovering how recent human history has affected whales.

Whale earwax has light and dark bands, with one of each made every year. The bands are caused by the different conditions the whales experience on their annual migrations (travel). This means that by studying the earwax, researchers can tell how old each band is.

Scientists in the United States have examined the levels of a stress hormone called cortisol in whale earwax samples from the last 100 years. The more cortisol in the band, the more stressed the whale was at the time.

The study showed that whales were most stressed when the whale hunting increased. World War II and global warming also seem to match increases in cortisol levels. These findings could help scientists protect whales from stressful situations in the future.

This is just the first of many possible tests that can be done with the whale earwax samples. Who knows what other information we might find?

This article was published in Issue 30 of Double Helix magazine (https://www.csiro.au/en/Education/Double-Helix). Copyright for this article is held by CSIRO.