>>JEREMY GOLDBOGEN: The first time I saw a blue whale lunge feeding event,
I almost couldn't believe it. It is absolutely a crazy feeding mechanism. The whale literally
doubles in size as it's feeding, so it's inflating at this really capacious ventral
feeding sac on the underside of the animal. So, it's literally inflating with water and food.
These questions come to mind—how does that work? how does that evolve? and how does
such a large whale feed on very, very small prey?—and these must be linked in some way.
>>DAVID CADE: So, this is actually a fin whale which is very closely related to a blue
whale. A fin whale is the second largest animal, probably, to have ever lived by mass. So, it
has that nice, streamlined shape and it's really easy for this whale to accelerate to high speed.
And as it does that, it rolls onto its side, it opens its mouth right at the krill patch, and then
as it engulfs this water you can see its pouch totally engulf all that huge amount of water.
And then it spends about 30 seconds to a minute or so actually filtering out all that water.
So, every rorqual lunge has those three phases. It has an
acceleration phase where it goes up to about three or four meters per second.
It has an engulfment phase which lasts about five seconds. And then it has that filtering phase.
It does this over and over and over and over again, sometimes a hundred times a day.
So, what's unique about our tags is that we were able to integrate not just the sensor data,
but also video. So, now we can see what the whale is actually doing from its own perspective.
Now this whale's out looking for food, so he's going to do one long breath and he's
going to dive down. So, he's going to dive down to about 100 meters here. So, he's diving down,
it's getting darker. And he’s gonna come up from below this prey patch. He's gonna start
maneuvering his body up towards this prey patch, accelerating up to about four meters a second.
A couple of big fluke strokes, and then right when he gets up to that prey patch he's gonna
open his mouth and engulf all that water and then, basically, start that filtering process.
So, you can tell that the whale's opening its mouth because you can see its normal head motions
and then you'll see the jaw actually separate. You can actually see the
whale's mouth the bottom of its jaw over there on the left-hand side.
The rotation of these jaws is amazing. These jaws are about- some of them on a big blue whale they
can be up to 12 or 13 feet long and it'll be just the jaws there. They sit in the whale's mouth,
kind of arched up like this, and then as that whale feeds, it opens it up, basically doubling
the area that it can engulf. And so it's like- imagine, like, a whole wall of this room coming
at you. It's engulfing all that water and then as it starts to close its mouth, those jaws will
rotate back up, so you have a minimal area around the edge for the water to actually come back out.
>>GOLDBOGEN: The interesting thing about blue whales is that they evolved from
much smaller ancestors. So, about three to five million years ago. whales were
really dolphin-sized and the oceans went through a rapid series of changes.
The effect of those changes creates a lot of whale food and, really, these enormous patches—super,
super dense—and that's what makes their filter feeding mechanism so efficient and allows them
to evolve massive body sizes incredibly rapidly in just a small amount of geological time.
>>SHIREL KAHANE-RAPPORT: This diagram shows a blue whale with its pouch, the engulfment capacity,
fully expanded and it shows the model that we have created to measure how much water it can
swallow in one gulp. And whales, when they engulf water like this, they're also engulfing prey. So,
the more prey you can engulf at once, the more efficient you are and you get so much
more energy for that singular effort. And so, we think that whales have gotten so big
because they're able to engulf huge amounts of energy in a really efficient way.
>>CADE: Last week we put out 14 different types of tags.
If you're putting a camera on a whale, you can only tell so much. You have to have the context,
the interpretation of what's actually happening here. The most common whale behavior is just
gliding, just hanging out. And if you have to just watch this video with no context,
you could spend your whole career just basically watching whales do nothing, right.
So, one of the things that's really important in the work that we do is do the interpretation.
The blue line here is the depth sensor of the whale. So, that's a pressure sensor that measures
how much pressure is being applied to that whale. And so, then you can interpret that as depth and
how deep that whale actually is. The orange line here is the animal's speed. When the animal is
going faster that line is a little bit higher. This red line here is where we are in the video.
So, right now the whale is coming back up towards the surface. It's about to break the surface here.
And then goes back down. You can see that it's going to do about one, two,
three, four, five breaths and then go back down.
The pink line here is a measurement- we call it the animal's jerk. Jerk is the
rate of change of acceleration. In addition to the video we can use all those sensors to
actually construct a model of what that whale is doing in space and time.
How is it actually oriented in relation to the surface, in relation to everything else?
So, if I'm looking for interesting areas of this whale's behavior I’m looking at this graph and
saying, like, “Okay, well, what's interesting? What's unique? What's actually going on here in
interesting environments?” And the first thing that catches my eye is this peak and speed here
with a rapid deceleration phase. So, I know that something's going on there. I
know that you have a big event going on at that moment and that is the feeding event.
So, the whale here is doing its acceleration phase—
really pumping its tail, accelerating up there, opening its mouth, and then feeding as it decelerates.
There's that pouch. It inflates with water and it slows that whale down from all that drag.
Imagine, like, trying to force equal to your body weight amount of water. That whale is using its
momentum and then forcing that water forward as it then starts to filter that water out.