- Each year, gray whales make what is often considered the longest migration of any mammal on earth.

They swim from the Arctic to Baja, California Mexico, where thousands congregate to breed, give birth, and nourish new calves, and they can be shockingly friendly, even curious to tourists.

So in 2019, when hundreds started washing up dead people took notice and scientists called it an unusual mortality event, a classification, demanding immediate response.

- Another gray whale was found dead, which marks five reported strandings just this month.

- They went from being heavily depleted, almost near extinction, from commercial wailing to making this amazing recovery just up, up, up to the point where they were removed from the Endangered Species Act.

And then right around when that happens, suddenly you have hundreds of whales dying, washing up dead on the beaches.

And there was this big question of, you know, is there just a a cap for how many whales the Arctic can support?

And suddenly they've hit carrying capacity.

- And it's not only scientists and tourists that took notice when whale populations decrease, they're also an intimate part of many native cultures.

- There's a void there.

You know, there's a void in, in our culture, in our spiritual practices, and that has an impact on the health of our people.

- Gray whales don't eat during their 10,000 mile round trip migration until they get back to the Arctic.

So you'd think melting sea ice would be the culprit.

But low sea ice years have historically been good for great whale birth rates because it opens up feeding areas earlier.

- We as a community felt like we kind of had a pretty good sense of what was driving the birth rates in the population until we didn't.

All of a sudden, you know, that starts falling apart.

And so we felt like, hey, there's probably something else going on.

- The Arctic is warming four times faster than the global average with significant impacts on sea ice.

Over the last four decades, 2023 hit a record, low maximum extent, but until now, these changes haven't seemed to impact.

Gray whales.

- Gray whales make this extraordinary migration from the breeding areas in Baja, California, Mexico to get up to the Bering Sea.

And there is this really extraordinarily productive shallow basin that kind of straddles the Bering Straits and the Southern Chukchi Sea.

And that is where they go, and they just gorge themselves for four or five months.

- They won't eat again until they make the whole round trip journey back to the Arctic.

So changes there can have an impact on the population.

- For almost 20 years, there was this really tight relationship between sea ice and birth rates and gray whales, and it was a negative relationship, so it was more sea ice means fewer calves in the short term.

Less ice can be good for whales because it gets them onto their feeding ground sooner.

It gives them more time to feed.

- But there were clear signs that the problem wasn't simply vessel strikes or entanglement, and maybe not even an increase in marine heatwaves.

- During these mortality events, we saw really, really skinny whales.

All signs are pointing to, it's probably something about their food and their food is in the arctic, - But studies had already shown that the abundance of prey in the Chirikov Basin hadn't decreased.

So what was going on?

Other baleen whales like humpbacks or rights feed on plankton, krill or small fish in the water column, gray whales are also baleen whales.

But their favorite food is a high fat content amphipod that lives on the bottom of the sea floor or in the benthic zone.

- So they're actually going down to the sediment, they're sucking in a bunch of sediment, and they bring in all these amphipods, and then they spit out all the sediment and water.

- And this whole food web is dependent on sea ice.

We - zoom in on the, on the benthic amphipods, right?

The ones that gray whales like the most, the fattiest, the best prey.

They live in the sediment.

And the way that that sediment is essentially fertilized is you get algae growing on the underside of the sea ice, and that algae dies and it sinks to the bottom and it, you know, decomposes along the way.

And you get this huge influx of nutrients down into the benthic sea floor system.

And then you get these like ultra productive blooms of these little critters in the sediment.

And that's what gray whales and all these other species that migrate seasonally to the Arctic, that's what they're coming - For.

And these extra fatty amphipods just might hold the clue as to what's causing this gray wheel die off.

- The really interesting sort of shift in our thinking happened when we stopped looking at abundance of prey and started looking at biomass of prey.

- Size of these amphipods have gotten smaller, and that means you gets less bang for the buck so that you, your whale goes down and now instead of getting, you know, a bite of thousand of these big guys, they're getting a thousand of littler.

And that means you're getting less calories per - Bite.

That is when suddenly we see this amazing signal that lines up almost perfectly with births in the population, deaths in the population, and stranding rates and body condition.

And it has led to a complete revolution in our understanding of how the Arctic ecosystem is being impacted by climate change.

- In the old days, back in the seventies and eighties, we had a lot of ice.

We even had multi-year ice, and that's ice that's grown one year, and then it freezes and it grows the second year or third year, and that's not happening.

Now.

- Normally the algae that grows on the bottom of the sea ice falls to the sea floor and feeds the anthrop pods.

But with sea ice melting earlier in the spring, the stability of the water column is disrupted and the algae doesn't make it to the sea floor to feed the anthrop pods.

- These animals, they, they build tubes.

They're not floating like the plankton.

They don't go with the water.

They live in the sediments, which means they get whatever comes down from the overlying water column.

And what's happening in this gray whale area in the coff is there's just not as much food going down to the bottom.

- As you have less sea ice, you have these blooms of algae in the, you know, in the ocean, but it's not the productivity on the sea floor.

- And less sea ice also means that currents in the cheer called basin have sped up, which sweep away the fine sediments that big fatty amphipods need to build their tubes.

These - Really high quality prey items for gray whales can't hang with those conditions.

They - Need food.

And so they either are gonna get it from the bottom in a traditional area, and there's not as much there.

So they're heading further north.

And now when you're further going further north, they're not alone.

They've got humpback whales that are feeding, they're feeding in the water column.

You have bow heads that are feeding in the water column.

And so if they're gonna switch to water column feeding on krill, they have competitors.

- But gray whales can be flexible.

Scientists have been studying a unique subgroup of gray whales that don't migrate to the Arctic, but instead congregate along the Pacific coast from Northern California to British Columbia.

- This is a really unusual group of about 200 to 300 animals that have evolved this different, basically lifestyle to feed in this unusual area with different feeding tactics.

They feed in these reefs habitats where it's super complex with kelp all over, and they do headstands, which literally is what it sounds like with the head down and the fluke up.

And then we also see them do these upside down swimming where they're kind of jaw snapping as they go along.

So, so it's very different than the typical gray whale benthic.

Feeding - Scientists still have a lot of questions about why this Pacific Coast Feeding Group formed, and recently Leigh's team made a new discovery.

- We've documented that these PCFG whales are up to meter smaller than those animals that go up to the Arctic.

You know, there's two sides to that coin.

One is that there's smaller, because they can't get enough energy to grow as big, but they could be smaller because it's, you know, the super shallow habitat with all this reef.

So being smaller is advantageous to be able to access that prey.

So at this point, we don't know which it is.

It's something I think about all the time almost.

- And it seems this subgroup of gray whales has not been impacted by the unusual mortality event.

So what does all of this mean for the future of great whales?

- The species as a whole has lived through dramatic changes from ice ages, which, you know, locked them out of their habitat up in the Arctic as well to periods of global warming.

So we know that they're adaptable and they're probably not gonna go extinct as a result of, you know, climate change in the near term.

But that doesn't mean that their populations aren't gonna be significantly altered.

So yeah, the long-term outlook for gray whales is not so great with less sea ice and dramatically declining sea ice.

- And these changes have real impacts on the Makah Nation who have been trying to reinstate their reserved treaty right to hunt whales for decades.

They've been waiting on a decision for the past couple years, but the unusual mortality event seems to have set back the timeline.

- You know, we don't call ourselves Makah, you know, we're qwidiččaʔa·tx̌, which, you know, loosely translated means the people that live among the rocks and the seagulls.

For us, whaling was the pinnacle, I guess, of, of our society.

You know, people call it a hunt.

It's often referred to as a hunt.

And images or thoughts that come to people's minds is, oh, it's just a big game hunt.

You know, it's like some safari trip where you're, you know, hunting these other large creatures.

And it's nothing like that at all.

To us, it's more than just subsistence.

It's more than just the cultural practices that developed around those resources for us.

You know, there's true spiritual connection to the ocean and what it provides for us.

When we stopped whaling in the 1920s, we did that on our own accord because, because of what we saw, you know, our, our hunts were, we were having to travel a lot further and, and they take a lot longer.

And, you know, so we moved away from our traditional activity well before, you know, the rest of the world did anything.

The number of whales that we're proposing over the course of, of time is, is not something that's gonna make or break that stock.

There are much bigger issues that should be addressed by both the US and the international community to make sure that that stock is healthy, that would make a more significant impact to the health of that stock than, than keeping the Makah from, from exercising its wailing rights under its treaty.

- And of course, these changes in sea ice aren't just affecting gray whales.

The Arctic may seem like a distant place for most of us, but changes there have real implications on the rest of the globe.

Gray whales might just be a warning for how out of balance our systems have gotten.

All right, guys.

I know this background is a little different.

We are actually out in California filming a scaled version of Weathered, which is really exciting.

So keep your eyes peeled for that.

But I do have some more information.

The Makah tribe just made huge progress in getting their whaling rights reinstated.

We're gonna link to that article, but we also wanna know what you think in the comments below as well.