A Chronicle of a Whale's Life, Captured in Earwax
Friday, September 20, 2013
Tree rings can tell a story about the environmental conditions a tree faced over its lifetime. Similarly, plugs of blue whale earwax can provide information on the mammal's heath, chronicling pesticide exposure, stress levels, sexual maturity, and more. Sascha Usenko and Stephen Trumble of Baylor University explain how.
JOHN DANKOSKY, HOST:
Now you've probably seen a cutaway section of a tree trunk, those rings inside? Well, they tell a story about the conditions the tree faced year after year. It turns out that whales contain a similar record inside their ears. Joining me now to talk about it are two researchers looking into this record. Stephen Trumble is an assistant professor of biology. Sascha Usenko is an assistant professor of environmental science. They're both at Baylor University in Waco, Texas. Welcome to SCIENCE FRIDAY.
STEPHEN TRUMBLE: How are you doing, John?
SASCHA USENKO: Thank you.
DANKOSKY: Oh, doing well. So, Stephen Trumble, tell us about whales. They have ears? I didn't know.
TRUMBLE: Well, like mammals, yes, they have ears. Not the kind of ear that you would expect or used to, but yes, they have ears. They don't have the external pinna like you would expect to see on your neighbor there, but they have ears. And they actually hear.
DANKOSKY: And, of course, they hear but are they hearing mostly with this apparatus that is the ear, or are they hearing through other parts of their body?
TRUMBLE: Well, kind of a consensus is that there are some fat deposits that are kind of made up into the jawbone of those large beasts. And the sound actually travels through the front part of the head and is kind of funneled into the eardrum apparatus.
DANKOSKY: I'm John Dankosky, and this is SCIENCE FRIDAY from NPR. And we're talking about a new study that has to with whale earwax, of all things. Sascha Usenko, we think of earwax as a kind of soft material. So maybe you can tell us about the wax that is inside the ears of these big whales.
USENKO: Well, it's - I mean, its wax are very similar to yours. It's a lipid-rich matrices. It's got a fibrous, brownish color, yellow color to it. But it's fairly consistent. It's more robust than your wax. It's a - but it's substantial.
DANKOSKY: Now, tell us about the rings that you're finding in here. What are you able to learn by cutting through, looking into the earwax of a whale?
USENKO: Well, what we're able to is essentially to go back in time. You know, similarly, you mentioned the tree rings. The farther we go into the center of the tree, the farther we're going back in time. And so when we actually cut the earplug in half, we can actually see the light and dark lamina or layers in there. And so when we measure contaminates or hormones or mercury in each layer, the farther we go towards the center, the father back in time we go. And so, really, for the first time, we're able to reconstruct an animal's lifetime chemical exposure, or for the natural hormones, the chemical profile.
DANKOSKY: Now, obviously, for a long time, you've been able to study this to a certain extend in whale, but you're finding it in their blabber. But you're able to find different things in this earwax, why?
USENKO: Well, the blabber actually just tells us that the animal was exposed to - if we look at the contaminants - exposed those contaminants. But the earwax allows us to understand when that occurred in the animal's lifetime. So it's a significant difference between those two matrices. But in blabber, typically, you might look at, you know, persist organic pollutants, organic pesticides such as DDT but - which we might expect to accumulate in those lipid matrices, these lipid tissues. But, you know, for us - Doctor Trumble and myself - were actually able to measure the less persistent or more degradable contaminants, such as the natural hormones, which also another advantage.
DANKOSKY: Now, I assumed that you had to get this whale earwax from a whale that is already deceased. Tell us about how you got this sample and how you might get more.
TRUMBLE: A particular, actually, initially, this came about - obviously, the question we had about aging animals. And with my background, I knew that earplugs had been used, historically, to age whales. And so Usenko and I had been chatting and got hold of the Smithsonian and Charlie Potter. And he sent an earplug we could kind of developed some methodology using this thing to see if we could actually do what we're kind of hypothesizing.
And once we've figured out that it actually worked, we contacted a friend of mine at Santa Barbara Museum of Natural History, Michelle Berman. And I said, you know, hey, we think we're on to something here. Do you think you could, you know, if you ever get an earplug in your holdings there, could you give me a holler. She's like, you're not going to believe this but we have a blue whale plug. And that's pretty much how it started. And it was sent to us and went from there.
DANKOSKY: And I assume that what you're putting out a call for is as many of these earplugs as possible. You could learn a lot more if you have more samples.
TRUMBLE: Absolutely. And the museums hold hundreds of these samples. They've been collecting through - collecting these things throughout the decades, from the 1950s. And, you know, I can get them from, you know, dead animals. So you can't, you know, swim out in the ocean, draw yourself earplug off a whale. This wouldn't work. So, you know, I get them from beached calves and things like that. So museums like - so they have, you know, Smithsonian alone has upwards of 500 of them identified so.
DANKOSKY: Well, I want to thank you both for talking to us about this unusual study and good luck in getting more of these families. Stephen Trumble, assistant professor of biology, Sascha Usenko, an assistant professor of environmental science. They're both at Baylor University in Waco, Texas. Thank you to you both.
USENKO: Thanks, John.
DANKOSKY: If you missed any part of this program or would like to hear it again, subscribe to our podcast, audio and video, on iTunes and Android apps. You can point your tablet or smartphone to our website, @sciencefriday.com, where you can also join our mailing list. If you like us, well, then like us on Facebook. You can also follow us on Twitter, @scifri. Always emails us. The address is email@example.com. In New York, I'm John Dankosky. Transcript provided by NPR, Copyright NPR.View this story on npr.org