This is scientific American 60 second science. I'm Christopher Intagiyata.

Blue whales are the largest animals ever to exist on Earth,

but they're still tough to track because they live underwater where we can't easily see them,

and often in remote areas, like the southern ocean.

But the whale's songs can travel hundreds of kilometers underwater,

so scientists often listen for them instead.

By the way, that's sped up on time so you can hear it.

Over the years, these eavesdropping biologists have noticed a mysterious trend that certain blue whale calls are gradually lowering in

pitch over time. For example, here's a call from 2002 followed by one from 2017.

It has been observed for many blue white population worldwide.

So this phenomenon has to have a worldwide explanation.

Emmanuel L'wa is a bioacoustician at the University of New South. explanation. The phenomenon holds true for populations of blue whales in the southern Indian Ocean too.

And they suggest one reason maybe that whale numbers have rebounded from the days of Captain Ahab.

More whales means individuals don't have to shout as loud to be heard by other

whales and because of an anatomical peculiarity in the way whales sing the

softer they sing the lower the pitch. The scientists have another theory too, which may be acting in concert with the first, which is

that whales are singing more softly and therefore more deeply because increasingly acidic ocean waters carry their calls further.

The full write-up is in the Journal of Geophysical Research Oceans.

LaWauinertime noticed one other short-term trend, that Southern Blue Whales songs actually get higher in pitch during the

Austral summer, perhaps in an effort to be heard over cracking icebergs.

Like when you put some ice cube in your drink you can hear it crack so it's the same for an iceberg

So it will be really loud and you can hear it across an oceanic basin

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