Why Does Whale Feeding Behavior Matter?
Why Does Whale Feeding Behavior Matter?
Giants of the Sea, Part 4
An aerial view of a blue whale gliding near the ocean’s surface. The Museum’s logo unfolds across the screen, reading “150 Years | American Museum of Natural History.” It fades away. A title animates in, reading, “Giants of the Sea, Part 4: Why does a whale’s feeding behavior matter?”
DAVID CADE (Postdoctoral Researcher, Institute of Marine Sciences, UC Santa Cruz): The whale behavior is only half the story if you want to study feeding, right. You also want to look at the context of how much prey there is and where is it located.
Researchers on a small boat in icy waters are captured by the rear camera of a tag attached to a whale’s back as it dives below the surface. As the camera passes the bottom of the boat, a box-like electronic device can be seen jutting below the propeller.
CADE: The way we do that is we've rigged up a system on the back of our boats that actually has these echosounders on there that allow us to determine the density and distribution of prey in the water column.
Jeremy Goldbogen interviewed in an office space, with computer monitors behind. Text animates on screen, identifying him as Jeremy Goldbogen, Assistant Professor of Biology, Hopkins Marine Station of Stanford University.
JEREMY GOLDBOGEN (Assistant Professor of Biology, Hopkins Marine Station of Stanford University): So, there's a saying on the California coast called “wind to whales.”
Gulls fly over a beach at sunset, as waves crash to shore. An illustrated cutaway of the California coast shows the beach sloping down to the sea floor and a floating blue whale.
GOLDBOGEN: And so, every spring we get really, really high winds and that creates upwelling.
Two arrows appear, pointing in a parallel direction to the sandy beach. Text on them reads, “surface winds.”
GOLDBOGEN: So, those winds basically take the surface waters away from the coast…
J-shaped arrows curve along the coastline and then turn perpendicular from the surface winds, out towards sea.
GOLDBOGEN: …and that's replaced with really nutrient rich deep water.
Blue arrows, indicating colder temperatures, curve up from the sea floor towards the coastline. As they turn up the slope, they become red (warmer), and turn back out to sea.
Goldbogen speaks from his office.
GOLDBOGEN: And so, that in turn causes a trophic cascade—
The arrows representing winds and currents in the illustrated diagram move in animated loops. An inset of microscopic ocean organisms pops out.
GOLDBOGEN: …all of those rich nutrients will allow the phytoplankton to bloom. It also, in turn, allows the zooplankton and the krill to bloom.
Goldbogen speaks from his office.
GOLDBOGEN: So, that's why it's a very seasonal pattern of krill going boom and bust throughout the foraging season for blue whales.
David Cade interviewed in an office space. Text animates on screen, identifying him as David Cade, Postdoctoral Researcher, Institute of Marine Sciences, UC Santa Cruz.
DAVID CADE (Postdoctoral Researcher, Institute of Marine Sciences, UC Santa Cruz): So, what the echosounder allows us to do is actually determine the density and distribution of prey in the water column.
Cade indicates a graph on his computer monitor. Labels on the y-axis read “75m, 100m, 125m, 150m,” and on the x-axis read, “1km, 2km,” etc.
CADE: So, if you look at this graph, on the vertical axis you have the depth. On the horizontal axis you have, essentially, time or distance.
Cade speaks in his office, indicating the graph on the computer monitor.
CADE: The ship moves across the surface of the water. It's actually mapping—each one of these vertical lines is one individual ping where it's listening for the return echo.
An animated rubber boat moves through the ocean. Curved lines expand out into the water from an echosounder positioned on the bottom of the boat. As it passes over a patch of krill, the curved lines are reflected back towards the boat.
CADE: How strongly that signal bounces off of an object in the water tells you how much of it there is and how far away it is.
Cade speaks in his office.
CADE: If that click [MAKES A CLICKING NOISE] takes longer for it to come back that means that the object it's bouncing off of is further away.
The echo-sounding graph is shown in full. A spiky shape indicates the signals received as the boat travels. A significant amount of red can be seen throughout, indicating high density in the water column.
CADE: The louder it comes back, the more stuff there is in the water. So, what this is, is then a map of the loudness of the return signal and the red areas are areas of high intensity. That's an area where you have a lot of stuff in the water column.
Cade speaks in his office.
CADE: In this case, it's krill. The white areas mean that that sound just traveled through there without bouncing off of anything. The blue areas are areas where there's a little bit of stuff in the water but not so much in there. So, then because we've done, then, these finely calibrated experiments, we can actually tell you how much krill that actually corresponds to.
Cade, Goldbogen, and other researchers confer over a laptop.
GOLDBOGEN: So, we think that krill will migrate deep into the ocean during the day to avoid predation from other predators,
Goldbogen speaks in his office.
GOLDBOGEN: …but also because they're deep and aggregated, trying to avoid predators, blue whales appear to have evolved foraging strategies that take advantage of that dense patchiness at depth.
Goldbogen confers with Cade, as the two review images on a computer monitor.
GOLDBOGEN: Understanding the vital rates of an animal, such as how an animal feeds and its feeding rate, is really fundamental to the conservation and management of these animals. Because blue whales are specialists on a very specific resource, we have very good studies and models…
Goldbogen speaks in his office.
GOLDBOGEN: …that can tell us exactly what the energetic efficiencies are of blue whales, especially how it relates to changes in their food supply.
Cade speaks in his office.
CADE: One of the things that we have to monitor and think about and predict into the future is as the oceans warm and if they continue to warm at the current rate how that might affect those oceanographic processes,
Animated diagram of the ocean winds and current patterns along the California coastline.
CADE: …how that might affect upwelling which leads to these big blooms, which lead to these krill hot spots.
Cade speaks in his office.
CADE: As the ocean warms, those processes might change and how those are going to be changed is a matter of a big scientific debate. Like, is there going to be increased upwelling or is there going to be- or will warmer surface waters lead to increased stratification that inhibits that cold, cold bottom water, that nutrient-rich bottom water from coming up to the surface and providing nutrients to the phytoplankton that everything in the ocean thrives on.
A field of bubbles rises up through the ocean. A blue whale swims underwater.
CADE: So, how climate change is going to affect these blue whale populations is unknown, but it will probably have a big effect one way or the other.
Goldbogen speaks in his office.
GOLDBOGEN: Blue whales face a number of different threats due to our increasingly urbanized oceans.
Still image of a whale’s tale flapping above the ocean’s surface, while in the background, a large commercial ship looms on the horizon.
GOLDBOGEN: One specific threat relates to ship strikes.
Goldbogen and Cade confer at a computer workstation.
GOLDBOGEN: Our tags give us a really detailed view of where these foraging hot spots intersect with the shipping lanes.
A graphic indicating the locations of documented ship passages to blue whales’ feeding areas off the coast of southern California. Lines indicating shipping lanes pass very close or directly over whale locations.
GOLDBOGEN: And if those foraging hotspots change, hopefully in the future we can have a dynamic management solution where we can say,
Goldbogen speaks in his office.
GOLDBOGEN: “Hey, we're predicting that the foraging hotspot is actually going to move west and perhaps if we just move the shipping lanes a little bit to this side or a little bit to this side,
Still image of a whale’s back breaching above the surface with a large commercial ship in the background.
GOLDBOGEN: …we can significantly decrease the amount of ship strikes that occur.”
Goldbogen speaks in his lab.
GOLDBOGEN: Because blue whales are such tremendous filter feeders—they process vast amounts of the ocean—we think that they might be susceptible to ingesting microplastics…
Goldbogen and other researchers handle equipment on a boat.
GOLDBOGEN: …and they might be sentinels for ocean pollution, specifically microplastics.
MATT SAVOCA (Postdoctoral Research Fellow, Hopkins Marine Station of Stanford University): One of the ways to determine what you're eating is to look at what you're pooping out.
Close-up of a hand holding a mason jar with a frosty red substance inside.
SAVOCA: And so, what we have here is a fecal sample from a blue whale…
Savoca speaks to camera in an equipment room, holding the whale poop. Text identifies him as Matt Savoca, Postdoctoral Research Fellow, Hopkins Marine Station of Stanford University.
SAVOCA: …that we collected in Monterey Bay last summer. The reason why it's deep red like that is because they eat krill. Blue whales, especially, eat only krill and krill are this dark, you know, deep orange and red color.
Goldbogen and other researchers operate equipment on a boat, pumping up water from the ocean.
SAVOCA: And what we intend to do is analyze these samples to look for plastics within the fecal sample.
Cade speaks over a CB radio on a boat.
CADE: Martin, Musculus.
Drone footage of a research vessel in the ocean. On board, Cade operates equipment and plugs in a laptop.
CADE: Blue whales are coming back from centuries of exploitation. These new devices have really, like, opened up a whole new world for studying these animals that we really know so little about.
Close-up of a computer monitor showing a research paper by Goldbogen, et al., entitled, “Why whales are big but not bigger: Physiological drivers and ecological limits in the age of ocean giants.” Camera pulls back to reveal Goldbogen at his desk.
GOLDBOGEN: Every time we’ve learned something, there's actually 10 more questions that pop up.
Goldbogen speaks in his office.
GOLDBOGEN: How blue whales migrate across the ocean from their breeding grounds to their feeding grounds…
A rubber motorboat pulls behind a blue whale. A researcher with a long tagging pole stands in the bow.
GOLDBOGEN: …and how they impact the resources that the entire ocean ecosystems rely on is really interesting and important.
The researcher successfully tags the whale as it spouts and then dives below.
GOLDBOGEN: And that's why we should try to better understand these ocean giants.
[EXCITED YELL]
Credits roll:
The “Marine Biology” Seminars on Science is made possible by OceanX, an initiative of the Dalio Foundation, as a part of its generous support of the special exhibition Unseen Oceans and its related educational activities.
Director / Producer
Karen Taber
Producer / Editor
Ben Tudhope
Post Producer
Kate Walker
Title Design
Timothy J. Lee
Illustrations
Alex Boersma
Special Thanks
The Goldbogen Lab at Hopkins Marine Station of Stanford University.
All footage & images taken under permit NMFS 16111/21678.
© American Museum of Natural History
To help preserve populations of the endangered blue whale, researchers are analyzing everything from high-tech sensor data to whale poop. In Part Four of our four-part Giants of the Sea series, learn how scientists are gathering information that could help us find conservation solutions in the face of threats like climate change and vessel strikes.