Usually earwax is considered pretty gross — but when it comes to whales, earwax is super exciting stuff.
That's because, according to NatGeo, scientists can use the foot-long earwax tubes to tell how old a whale is, and what sorts of stressors it encountered in its lifetime.
Much like the rings on a trunk can age a tree, the rings of whale earwax tubes can also determine its age.
According to NatGeo, each ring is equal to about six months in a whale's lifetime. So having 24 rings means a whale was 12 years old when the wax was harvested.
But beyond age, the wax gives insight to so much more about a whale's lifetime.
Smithsonian magazine reported that scientists can study the hormonal and chemical makeups of these rings to see when a whale went through major life events like sexual maturity, pregnancy and birth.
The same research can be applied to provide context about how stressed or not whales have been over time.
NatGeo reported that scientists can look at the cortisol levels in each ring to determine whether the animal was producing more of the stress hormone at a certain time.
For example, from the late 1800s through the 1970s, fin, humpback and blue whales were hitting higher stress levels, likely due to commercial whaling activities — which were eventually halted by a worldwide moratorium in the '80s.
Also notable was that whales were more stressed from 1939 to 1945 — during World War II — when ship, bomb and plane noises would have been increased in the whales' habitats.
From 1990 until now, the rings show that as the ocean temperatures have risen, so have the whales' stress levels.
And while earwax is obviously very important for researchers, it's also pretty useful for the whales themselves.
According to Healthline, human earwax is mostly there to keep dust and water out of our ear canals — but a buildup can make hearing harder. Meanwhile, whale earwax pretty much does the opposite — it actually helps whales hear better.
The Smithsonian noted that the long wax tubes actually act as a sort of hearing aid for the whale. The wax and the ocean water are the same density, so sound can be funneled directly into the ear without any distractions.
If the whale's ear was full of air, the sound would be blocked by the difference in density.
Whale earwax can only be harvested from dead whales, but the specimens that scientists already have can help show the world the effect we're having on whales over time.
NatGeo noted that the wax can kind of act like canaries do in mines by signaling trouble for whales and the environment before it's too late to fix it.