Blue whale
Blue whaleShutterstock


The novel approach allowed the researchers to gather hormonal and chemical information preserved from birth, when whales begin to accumulate the cerumen (ear wax) up until death. Year after year the wax builds up in layers and the hard substance remains, allowing marine biologists to use the number of layers as a signifier of a whale's age. However a team at Baylor University wondered what other hidden secrets the wax contained, and after getting hold of a particularly meaty 25.4cm-long specimen, they found the answer was a great deal. In fact, something almost unheard of in nature -- a lifetime biological record. Usually, measuring things like hormone levels in animals involves taking blood or tissue samples, something that proves tricky in the wild open ocean.


"You have this 100-year-old question: How are we impacting these animals? There is ship traffic, environmental noise, climate change and contaminants. Now, we are able to provide definitive answers by analysing whale earwax plugs," Sascha Usenko, assistant professor of environmental science in Baylor's College of Arts and Sciences, said in a statement.

Among the key finds were the amounts of Persistent Organic Pollutants (including pesticides and flame retardants) present and when they were transferred to the whale. The team found that maternal transfer was responsible for 20 percent of all POPs present, from before birth up until 12 months.

"The POP burden measured in each lamina [layer of wax] suggests that contaminants are recirculating throughout the body during both periods of feeding and fasting," write the authors in the paper, published in Proceedings of the National Academy of Sciences

Also measured were the amounts of mercury. The team recorded two "pulse" events when the levels spiked. It's presumed these are associated with the whale entering a particular region, and since the whale in question was killed by a passing ship off the coast of California it's likely the spikes were due to environmental factors created by localised human impact.

The team is optimistic about the impact of its research, saying "We anticipate that this technique will fundamentally transform our ability to assess human impact on these environmental sentinels and their ecosystems". However, the technique has also proven to be an excellent method for investigating the blue whale's sexual maturity and life events. For instance, levels of testosterone present confirmed when the whale reached sexual maturity, while cortisol levels (stress hormones) mirrored key life events. For example, cortisol levels peaked at around 126 to 132 months and followed the largest peak in testosterone levels from 114 to 126 months of age, suggesting stress levels were a result of the whale engaging in breeding competition or other social events associated with reaching sexual maturity.

Spikes in stress levels may also be a result of environmental factors -- if fish stocks are low and the whales have to compete for food, for instance.

Combined with other ecological reports and measures, the earwax could unravel the total human impact on an ecology that is so hard to measure deep beneath the ocean surface.


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