Historic Abundance of Blue Whales Returns in California

This is Scientific American 60-Second Earth. I'm David Biello. Your minute begins now.
The largest animal on Earth is thriving anew, at least off of California.
And all it took was for people to stop hunting blue whales.
That's according to a new study in Marine Mammal Science.
Today, the California group of the mighty blue whales numbers roughly 2,200, according to conservationists and based on distinctive singing.
That compares with the more than 3,000 killed over the first seven decades of the 20th century.
The blue whale can grow up to 30 meters in length and weigh more than 180 metric tons,
and requires for food each day roughly 40 million tiny sea creatures called krill.
This may explain why the number of whales of California has stopped growing.
Some conservationists had argued that individuals being hit and killed by ship traffic held back population growth.
But the new research suggests it's more likely that California blue whales have reached the limits to growth in that region of the eastern Pacific Ocean.
Of course, more than 350,000 blue whales were killed in other parts of the world in the 20th century.
So the species has hardly recovered to its historical abundance.
But, at least in California, the blue whale is back.
Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.