Whale Song

I have not real comment here other than I find this piece of data on the songs of blue whales quite interesting:

The best records exist for the whales off California, and they showed that the whales sing at a frequency 31% lower than they did in the 1960s, when blue whales around the world had been commercially hunted to the brink of extinction.

The article notes that the frequency of blue whale song has been decreasing over time in all areas of the world. Read the article for conjecture on the "why" - but it may simply be that higher populations of blue whales means their song doesn't have to travel as far to reach others so they can sing at a lower frequency and still be heard over other noises in the ocean.