Throughout their lives, blue whales accumulate layers of wax in the ear canal that form a plug, almost a foot long, and which remain permanently in place until they die. Scientists from Texas have analysed these layers, in a manner similar to tree rings, to roughly estimate a specific whale’s age, track changes in its hormone levels, and see which chemicals it was exposed to in the ocean, the Daily Mail reports.
Scientists from Texas used chemicals found in the earwax from an endangered blue whale, similar to the one pictured, to discover what its environment was like when it died, along with other clues about how it lived and even when it reached sexual maturity.
This wax can also be used by researchers to work out what needs to be done to protect them from stress, pollution and other threats in the future. Dr Sascha Usenko from Baylor University made the breakthrough by using the wax from a dead 12- year-old blue whale.
He found fluctuating levels of testosterone and the stress hormone, cortisol, during its life. At the time of its death, Usenko said the whale had twice as much cortisol in its blood than at any other point.
He believes this could relate to food availability, changes in social status, pollution exposure and environmental noise. While, testosterone levels suggest the male blue whale reached sexual maturity at about 10 years of age.
“The general increase in cortisol over the animal’s lifetime could be associated with a multitude of factors including weaning, development, sexual maturity, migration, food availability, environmental conditions, changes in social status, accumulated contaminant exposure or environmental noise,” said Usenko.
“The use of a whale earplug to reconstruct lifetime chemical profiles will allow for a more comprehensive examination of stress, development, and contaminant exposure, as well as improve the assessment of contaminant use or emission, environmental noise, ship traffic and climate change,” Usenko said.
The findings were reported in the Proceedings of the National Academy of Sciences journal.
