We saved gray whales from extinction. Why are so many dying again?

Summary

Podcast Summary: Short Wave

Episode Title: We saved gray whales from extinction. Why are so many dying again?

Date: March 11, 2026
Host: Regina Barber (NPR)
Guest: Joshua Stewart, Marine Ecologist at Oregon State University

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Overview

This episode of Short Wave explores the troubling resurgence of mass gray whale deaths along the west coast of North America, decades after successful conservation efforts brought the species back from the brink of extinction. Host Regina Barber and marine ecologist Joshua Stewart discuss the cyclical nature of these die-offs, the puzzles they posed to scientists, and the surprising discoveries about the underlying causes—revealing important lessons about ecosystem resilience, natural cycles, and climate change.

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Key Discussion Points & Insights

1. Historical Decline and Recovery of Gray Whales

• Whaling's Toll:
  • Joshua Stewart (00:23): "Humans killed around 3 million whales in a period of like 70 years or so."
  • By the 1980s, gray whale populations had dropped to 5% of historic numbers.
• Public Awareness & Conservation:
  • Noted the impactful moment when whale songs were released on vinyl, igniting public empathy and the modern conservation movement.
  • Joshua Stewart (01:03): “Folks said, wow, how could we possibly be killing these animals? We have to stop this.”
• Success Story:
  • The international moratorium on whaling (1980s) brought about population recovery.
  • By 1994, gray whales were removed from the endangered species list.
  • Regina Barber (01:18): "Numbers rebounded so much that the gray whale was officially removed from the endangered species list."

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2. The Mysterious Mass Deaths

• Initial Die-Offs (1999–2000):
  • Hundreds of whales washed up dead, and estimates suggested thousands more died unseen.
  • Regina Barber (01:51): “Scientists estimated thousands of whales died, accounting for about a quarter of the population.”
• A Cycle Emerges:
  • 2019 saw a resurgence of mass deaths still ongoing at the time of the episode.
  • The deaths puzzled both the public and scientific community.
• Government Response:
  • Teams of experts formed to investigate, including Joshua Stewart.
  • Joshua Stewart (03:40): "When you have hundreds of whales wash up dead on a beach, people take notice...and the government jumps into action."

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3. Scientific Investigation and Breakthrough

• Discovery of Population Cycles:
  • Researchers identified "boom and bust" cycles in gray whale populations—not seen previously in such long-lived animals.
  • Large deaths (20–30% of population) would occur rapidly, with slower recovery following.
  • Joshua Stewart (04:30): "You can have, in this population alone, 20 to 30% of the population die off in two, three, four years."
• Not Disease, but Food:
  • While disease was considered, an unexpected email pointed to food supply as the true driver.
  • Arctic feeding grounds supply nearly all the energy for gray whales for the year.
  • Stewart's colleague, Jackie Griebeyer, provided key data:
    • Aligning cycles of Arctic sea floor “benthic” critter abundance (gray whale food) with whale population booms and busts.
    • Joshua Stewart (06:32): "The cycle that these little benthic crustaceans are showing perfectly aligns with these gray whale booms and busts. You never see that kind of like perfect alignment in your data. Wow.”
• Surprise in Scale:
  • While food-limited cycles are well-known in small or short-lived animals, such dramatic swings were unexpected in giant, long-lived mammals.
  • Joshua Stewart (07:54): "We're seeing these booms and busts which you expect to see in short lived small critters... Those aren't really the patterns that you expect to see in an animal like that."

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4. Analyzing the Cause: Carrying Capacity and Climate

• Natural Cycle—With a Catch:
  • The whale boom-bust pattern seems a natural outcome once populations reach “carrying capacity”—the maximum number a habitat can support.
  • Fluctuations in food matter more as populations rebound and competition increases.
  • Joshua Stewart (08:17): “Once you get to carrying capacity…and you’re competing furiously with all of your…competitors, you’re much more sensitive to those fluctuations in the environment.”
• Human Role and (Un)controllability:
  • Once the cause is determined as prey availability, human options for intervention are limited.
  • However, scientists urge due diligence in always confirming that nothing new or human-induced (pollution, disease, shipping) is driving die-offs.
  • Joshua Stewart (09:25): “There’s really probably nothing we can do about these natural cycles… Now that doesn’t mean...we should just say, ‘ah, no big deal...’ We still want to confirm… what is driving that die off.”
• The Climate Factor:
  • Current cycles are being disrupted by lasting shifts in Arctic food webs, likely due to climate change.
  • The latest die-off (since 2019) is more severe and prolonged, with very low birth rates preventing recovery.
  • Joshua Stewart (10:44): “This one has been going on pretty much non stop since 2019…we’re pretty sure that that is being driven by climate impacts to their Arctic feeding areas.”

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5. Broader Lessons and Warnings

• Vulnerable Successes:
  • Ironically, populations that have recovered most impressively may now be at greatest risk from environmental change.
  • Joshua Stewart (11:17): “There are these populations that are doing extremely well... But those are exactly the populations…where we’re going to see these big responses to changes in the environment, natural variability…but especially climate impacts.”
• Gray Whales as a Climate Alarm:
  • The struggles of gray whales serve as a “canary in the coal mine” for Arctic and marine ecosystem change.
  • Regina Barber (12:26): “But they're kind of like the canary in the coal mine for climate change.”
  • Joshua Stewart (12:30): “What we're seeing right now with gray whales is a climate alarm bell... we’re getting that signal from gray whales that things are fundamentally changing, they're changing fast and they're really being disrupted by these climate impacts.”

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Notable Quotes & Memorable Moments

• “Folks said, wow, how could we possibly be killing these animals? We have to stop this.” — Joshua Stewart (01:03)
• “And so you can have, in this population alone, 20 to 30% of the population die off in two, three, four years. And then in the past it’s turned around and recovered. And that to me is almost the more extraordinary part…” — Joshua Stewart (04:30)
• “The cycle that these little benthic crustaceans are showing perfectly aligns with these gray whale booms and busts. You never see that kind of like perfect alignment in your data. Wow.” — Joshua Stewart (06:32)
• “We're seeing these booms and busts…in animals… These old whales, they live for 70 years, they're enormous…Those aren't really the patterns that you expect to see in an animal like that.” — Joshua Stewart (07:54)
• “What we're seeing right now with gray whales is a climate alarm bell…” — Joshua Stewart (12:30)
• “My pleasure. I love whales.” — Joshua Stewart (13:11, closing moment)

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Key Segment Timestamps

• 00:23–01:18 — History of gray whale decline, public awakening, and conservation success
• 01:39–02:21 — Onset of mass die-offs (1999–2000) and estimations of death tolls
• 03:31–04:30 — Start of investigation; discovery of cyclical die-offs and surprising population dynamics
• 05:48–07:54 — Link between Arctic crustacean prey and whale population cycles
• 08:17–09:18 — Explanation of carrying capacity and why cycles emerge after recovery
• 10:10–10:44 — Role of climate change in most recent and persistent population decline
• 11:17–12:30 — Broader implications: recovered populations as early warning systems for environmental change
• 12:26–13:16 — Gray whales as climate indicators; final reflections

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Tone & Style

The conversation is accessible, curious, and lightly humorous, aiming to draw listeners into the scientific process while grappling with the emotional impact of wildlife loss and the paradoxes of conservation. There’s a persistent sense of marvel at nature’s complexity and a candid recognition of the limitations of human influence—except, crucially, when it comes to slowing or reversing climate change.

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Takeaway

Gray whales, once a symbol of conservation’s success, now serve as critical indicators of deeper environmental disruptions—reminding us that celebrating “recovery” is only one chapter in a much more complex and ongoing story shaped by natural cycles, but increasingly dominated by climate change.

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Transcript

[Announcer]

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[Regina Barber]

Consider the gray whale.

[Joshua Stewart]

Humans killed around 3 million whales in a period of like 70 years or so.

[Regina Barber]

In some species, like the gray whale, certain populations dropped to just 5% of their historic numbers.

[Joshua Stewart]

And we stopped hunting them pretty much because we'd killed so many of them that it was no longer economically viable to keep hunting them.

[Regina Barber]

That's Joshua Stewart, a marine ecologist at Oregon State University. And he says along the way, the public took notice after a biologist and conservationist named Roger Payne put whale songs on a vinyl record.

[Joshua Stewart]

And folks said, wow, how could we possibly be killing these animals? We have to stop this. So that was in the 70s. That was sort of the birth of the modern conservation movement.

[Regina Barber]

In the 1980s, the international moratorium on whaling went into effect and numbers started to climb all the way through 1994, when numbers rebounded so much that the gray whale was officially removed from the endangered species list. But then 1999 happened,

[Joshua Stewart]

and then hundreds of whales start washing up dead on beaches all along the west coast of the U.S. canada and Mexico. The same thing happens the next year in 2000. Hundreds more wash up dead.

[Regina Barber]

And these are just the whales that people see dead on the beach. It doesn't include the ones that die at sea during their more than 10,000 mile round trip migration to the Arctic. This is where they eat enough to last them the entire year. So Josh says scientists estimated thousands of whales died, accounting for about a quarter of the population.

[Joshua Stewart]

Everybody's wondering what caused this. We thought they were doing so well. Has something changed? Are they on their way back down?

[Regina Barber]

But then the deaths stopped. The whale population recovered, years went by and people moved on until a few years ago.

[Joshua Stewart]

20 years later, 20, 19, hundreds of gray whales start washing up dead again.

[Regina Barber]

And it's still happening today. Today on the show, a mass whale death mystery, how scientists figured it out and what it means for the species moving forward. Regina I'm Regina Barber, and you're listening to shortwave, the science podcast from npr.

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[Regina Barber]

Okay, Josh, let's pick up this story. So we're in 2019, all of the whales are dying off again. Then what happens?

[Joshua Stewart]

Yeah, so when you have hundreds of whales wash up dead on a beach, people take notice. We have, we have federal laws that are meant to protect and recover marine mammal populations. And so the government jumps into action in response to that and they get these teams together of experts to try to understand what is driving these mortality events. And so I was part of that effort.

[Regina Barber]

What did you find?

[Joshua Stewart]

So we looked at this and basically what we found was that after the population had recovered to that sort of pre whaling abundance or that carrying capacity, they're going through these cycles of booms and busts where it actually didn't just happen these two times in 1999 and then again in 2019, we found another major decline that happened 10 years before that in the 80s.

[Regina Barber]

Oh, wow.

[Joshua Stewart]

And so you can have, in this population alone, 20 to 30% of the population die off in two, three, four years. And then in the past it's turned around and recovered. And that to me is almost the more extraordinary part, that you can have this population recover that 20 or 30% also over a period of three to four years, it takes a little bit longer for them to recover than to die off. And so we're seeing these booms and busts which you expect to see in short lived small critters that reproduce really quickly. It's not something that we expected to see in animals. These old whales, they live for 70 years, they're enormous. They take a really long time to reach sexual maturity, take a long time to reproduce. Those aren't really the patterns that you expect to see in an animal like that. And a lot of people when they see that, they think, well, disease, you know, maybe this is a disease component that spreads and suddenly has a really strong impact and then maybe goes dormant for a while and comes back after a while. So there was a lot of emphasis looking for disease as a potential driver as well.

[Regina Barber]

Okay, so you're looking into this mystery, you find these cycles of boom and busts happening. And then a few years after these most recent mass die offs, you get an email from a colleague. What does she say?

[Joshua Stewart]

Yeah, so she, this is my colleague, Jackie Griebeyer, she's an Arctic scientist and she studies the little critters, the crustaceans that live in the sea floor. And this is what gray whales migrate all those thousands of kilometers to feed on every year.

[Regina Barber]

And so it's the only time they're eating, like you were saying.

[Joshua Stewart]

Yeah, exactly. So that whole. All of their energy for the entire year depends on how many of these little critters they can eat in that tiny window of three to five months in the summer. And so she's been going up to the Arctic on these cruises, collecting benthic grabs. They send a little claw down and it takes a sample of the mud, and then they count everything in it. They weigh everything in it.

[Regina Barber]

So a claw machine.

[Joshua Stewart]

It looks like a claw machine.

[Regina Barber]

That's the prize is plankton.

[Joshua Stewart]

Well, yeah, a bunch of dirt is your prize. So she's been studying these critters and these ecosystems for decades. And, and so she sends me the data on how much benthic biomass, how much weight, or average weight of these little crustaceans there are in the sediment. And I just roughly plot the data, and the cycle that these little benthic crustaceans are showing perfectly aligns with these gray whale booms and busts. You never see that kind of like perfect alignment in your data. Wow. And, you know, on one sense, it's, like, magical because it's one of the coolest experiences you can have as a scientist to just. You don't have to even use any fancy statistics, although I love using fancy statistics. You could just see that in the raw data that these two things line up perfectly. So in that sense, it was super cool. On the other hand, it's so simple and obvious that the food that they migrate, all this, you know, this way to go feed on, is what's driving their population dynamics. Of course it is. You know, there's no surprise there. And so the surprise is not necessarily the drivers, which is how much food they have to eat and how long they have to access that food. Up in the Arctic, the surprise is how dramatic the response to that prey limitation can be, because, again, you just don't expect to see that kind of response in a species like this.

[Regina Barber]

So this sounds like a natural cycle, is that right?

[Joshua Stewart]

Absolutely, yeah. So this, this is the. The interesting thing and where, you know, this story continues because we're seeing this for the first time in gray whales. But that was exactly my next question, which is, well, is there anything surprising about this, or is this exactly what we would expect to see? And what's unique about gray whales, in a sense, is just how well they've recovered? So they were one of the first whale populations or species to recover back to those levels that they were at before whaling. And so that is probably what triggered these events. And sort of our subsequent work that we've been doing is showing that actually once you get to carrying capacity and you've run out of food and you're competing furiously with all of your, well, they used to be your friends, but now they're your competitors, you're much more sensitive to those fluctuations in the environment. So if there's enough food for 25,000 whales and sometimes there's enough food for only 18,000 whales, if there are only 2,000 of you, you don't care. There's plenty of food up there, but once you're at that level, then those fluctuations start to matter. And so we only see these big booms and busts so far in these populations that have recovered up to those levels where they're really competing with each other for limited resources.

[Regina Barber]

So if this is a natural cycle, should humans do anything about this when they start seeing whales just dying?

[Joshua Stewart]

I know, it's a good question. So the deeply unsatisfying part is that there's really probably nothing that we can do about the, you know, these natural cycles. So once we find that, hey, this is driven by prey availability in the environment, there's not much more that we can do about that. Now that doesn't mean that when hundreds of whales wash up dead, we should just say, ah, no big deal, you know, it's probably natural. We still.

[Regina Barber]

They'll come back.

[Joshua Stewart]

Yeah, they'll come back. They came back before. We definitely still want to confirm, you know, what is driving that die off. Because there are many other things that could be driving it. We as humans are increasing our footprint in the oceans. We fish more, we ship more things, we have tons.

[Regina Barber]

Well, and that plankton cycle may be affected by climate change.

[Joshua Stewart]

Yeah, huh. That's a huge potential disruption. You know, we're moving out of a natural range of sort of variability and prey availability into this sort of new altered world where one of the biggest changes that we expect is just an overall reduction in the amount of plankton that's available on average. And so certainly we're seeing, I think that's what's happening in this most recent gray whale decline. It's much longer than previous boom.

[Regina Barber]

How long is it?

[Joshua Stewart]

So this one has been going on pretty much non stop since 2019 and the mortality rates have dropped off a little bit. Fewer whales are dying, but their birth rates have remained like rock bottom. So the population is not recovering the way that it did in previous years, and we're pretty sure that that is being driven by climate impacts to their Arctic feeding areas.

[Regina Barber]

So what are the larger lessons you think people should take away from this, like, whale mystery that you had a part in solving?

[Joshua Stewart]

Yeah, so there's. It's sort of a paradox, which is that there are these populations that are doing extremely well, and so they've made these amazing recoveries and we sort of thought we don't have to worry about them anymore. But those are exactly the populations, because they've reached this point where they're competing with each other, that we're going to see these big responses to changes in the environment, natural variability in the environment, but especially climate impacts, those are all going to show up first in these populations that we didn't think we needed to worry about anymore. And the sort of, like we said, the unsatisfying thing is that there's not necessarily something we can do about that, except stop climate change. That would be great, but we haven't been very good at doing that yet. So it's going to be really hard, I think, for the public, for managers, for scientists to deal with this when we've been saying for years, look at these amazing, successful recoveries. And then it's those populations where it's like, well, what the heck? Why are hundreds of these whales washing up dead? And how do you say to the public at that point, oh, don't worry about it, there's nothing we can do. It's going to be tough.

[Regina Barber]

But they're kind of like the canary in the coal mine for climate change.

[Joshua Stewart]

Yeah, absolutely. I mean, I think that what we're seeing right now with gray whales is a climate alarm bell because they're integrating what's happening in those ecosystems. It's easier for us to study what's going on with the gray whale population as they all migrate past us in California. It's much harder to have sort of a holistic assessment of what's happening in those really far flung Arctic ecosystems. But, yeah, we're getting that signal from gray whales that things are fundamentally changing, they're changing fast and they're really being disrupted by these climate impacts.

[Regina Barber]

Josh, thank you so much for coming on shortwave to talk to us about whales.

[Joshua Stewart]

My pleasure. I love whales.

[Regina Barber]

If you like this episode, please share it with a friend. It really helps our show. To hear more ocean science, check out our Sea Camp series. And it's a company newsletter equipped with ocean critter pics, deep dives into research and puzzles. We'll add links to our show notes. This episode was Produced by Burley McCoy, edited by our showrunner Rebecca Ramirez, and fact check checked by Tyler Jones. The audio engineer was Jimmy Keeley. I'm Regina Barber. Thank you for listening to Short Wave from npr.

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