Study Suggests Sperm Whales Herd Prey
JOE PALCA, host:
Just a few weeks ago on the show, you may remember we talked about huge numbers of large squid called Humboldt squid off the coast of California. Anglers in California have been reeling in boatloads of these guys, up to five feet long, weighing as much as 100 pounds, and reportedly pretty tasty. But we're not the only ones who like to eat calamari, Humboldt squid are also on the menu for big ocean predators like sperm whales.
And one place the sperm whales hunt down Humboldt squid is in the Sea of Cortez, between Baja California, and mainland Mexico, where the waters are just teeming with squid. But how do the big whales get the squid? Do they just gobble them up as the squid zip by? Well, new research on whales in the Sea of Cortez suggests that the whales have a more focused plan of attack. That research was presented at the American Geophysical Union's ocean sciences meeting in Portland, Oregon this week. I hope it's Oregon.
My next guest has been at the meeting all week and he's here to tell us about the study and some other news from the meetings. Sid Perkins is the earth sciences and paleontology writer for Science News in Washington, D.C. He joins us over the phone from Portland. I - is that Portland, Oregon, Sid?
Mr. SID PERKINS (Correspondent, Science News): It is Portland, Oregon, yes.
PALCA: Okay, good. So I'm in the right part of the world. Okay. So - and if you want to learn more about the meeting and Sid's coverage, you can go to sciencenews.org. But first, Sid, tell us about this trick that the sperm whales have learned to corral squid.
Mr. PERKINS: Well, this - yeah, this is a really interesting data from a couple of field seasons of looking at those whales there in the Gulf of California. And what these researchers have done is they've developed a tag that combines a GPS tracker which allows you to see their movements at the surface and other censors that will tell you the depth during the dive.
And these - this is the first type of tag to combine the both. And it took data every couple of seconds for up to a month, tracked all of their movements. Essentially, these are flight data recorders for whales. So what they had done was they had tagged three whales in a social group of about 10 to 15 whales. These are typically females and groups of females and calves.
And previously, the idea was that they'd form these groups to share the burden of rearing their calves or to ward off, you know, the unwanted advances of young, non-dominant males. But this study is the first to suggest they also collaborate when they hunt. And by downloading the data, comparing it, they were showing that during some periods, these whales that were tagged and presumably others in the group would simultaneously dive really deep, sometimes downward to around a kilometer of depth.
Mr. PERKINS: And researchers had thought they would all dive to a similar depth and just kind forage around. But the data is showing that typically two of the whales would go to the same depth, but the other one that was tagged would dive a few 100 meters deeper. And they would take turns doing that. I mean, some dives it would be one whale and the others would not dive deep.
And this is just that the whales may have been herding the prey and into those large schools often called bait balls.
Mr. PERKINS: And they would take turns lunging into the foray and feeding.
Mr. PERKINS: And, you know, porpoises and seals are noted to do this with fish, but in this case, presumably, the deep-diving whale is going to patrol in the bottom of the bait ball to keep the squid from escaping into the depths.
PALCA: Well, how do we know they're eating squid and not something else? I mean, you were only tagging the whales - not you, but the researchers were only tagging the whales, in this case, right?
Mr. PERKINS: Well, sure, yes. And, I mean, that's just one of their favorite prey items, I believe, from just, you know, monitoring stomach contents of other dead whales and things like that. And, indeed, one researcher told me this suggests but doesn't prove the notion of the tag team hunting particularly because you're not seeing what the prey is doing. And indeed, they don't even know that squid form these bait balls like fish do, but the researchers are now developing ways to track squid, sonar for example, so future work might strengthen the evidence for this collaborative hunting idea.
PALCA: Okay. Now, there was another study that I gather you covered while you were out there involving whales, but this had something to with industrial whaling and the carbon cycle. What's all that about?
Mr. PERKINS: Well, I mean, this is essentially looking at the carbon footprint of what's called industrial whaling, which really commenced in the early 1900s, when you got, you know, ships with engines and they were going out to essentially harvest lots of whales in the ocean for meat and for oil and whale oil and things like that.
Whales, as you know, are big. They...
PALCA: I've heard that, yeah.
Mr. PERKINS: They put on the weight. And as they put on the weight, they're packing on the pounds - they put on weight, they're packing on carbon. And they increase about one to 3 percent in weight each year. Blue whales, the largest creature that ever lived, can get up to be 90 tons. And besides being big, they're on the few creatures in the ocean that's very long lived. They can live up to a century or more.
So for both of those reasons, in marine ecosystems, whales are like forests. They hold a lot of carbon and they do it for a long time.
Mr. PERKINS: And this researcher looked at, again, the effect of industrial whaling during the 20th century. And in 1900, the researcher estimated that there was 110 million tons of whales in the ocean.
And of course, the large-scale whaling continued into the '70s, and there have been some recovery since then for some species. But overall, the researcher estimated that industrial - hello?
PALCA: Oh, I'm here. Yeah, go ahead.
Mr. PERKINS: Okay - estimated that industrial whaling during the 20th century returned about 105 million metric tons of carbon to the atmosphere, which is equivalent to about 385 million tons of carbon dioxide. And that's kind of small potatoes compared to the 7 billion tons of emissions that, you know, people generate each year. But it's not inconsiderable because that emission is equal to driving 128,000 Hummers for a century, or from burning all of the forests in New England at once.
PALCA: Wow. We're talking with Sid Perkins of Science News about the latest news from an ocean sciences meeting in Portland, Oregon. I'm Joe Palca, and this is SCIENCE FRIDAY from NPR.
All right, well, Sid, actually we've run out of time for that discussion. But thanks very much for bringing us up to date for that. And I guess you'll have reports on this and other things from the meeting at - in Science News this week.
Mr. PERKINS: They are on the Web site, yes.
PALCA: Okay. We'll scuttle on over there. Thanks very much for joining us.
Mr. PERKINS: Thanks for having me.