60 Minutes - 04/20/2025: Bird Flu, Demis Hassabis, Flight of the Monarchs

Episode Date: April 21, 2025

Bird flu, which has long been an emerging threat, took a significant turn in 2024 with the discovery that the virus had jumped from a wild bird to a cow. In just over a year, the pathogen has spread through dairy herds and poultry flocks across the United States. It has also infected people, resulting in 70 confirmed cases, including one fatality. Correspondent Bill Whitaker spoke with veterinarians and virologists who warn that, if unchecked, this outbreak could lead to a new pandemic. They also raise concerns about the Biden administration’s slow response in 2024 and now the Trump administration’s decision to lay off over 100 key scientists. Demis Hassabis, a pioneer in artificial intelligence, is shaping the future of humanity. As the CEO of Google DeepMind, he was first interviewed by correspondent Scott Pelley in 2023, during a time when chatbots marked the beginning of a new technological era. Since that interview, Hassabis has made headlines for his innovative work, including using an AI model to predict the structure of proteins, which earned him a Nobel Prize. Pelley returns to DeepMind’s headquarters in London to discuss what’s next for Hassabis, particularly his leadership in the effort to develop artificial general intelligence (AGI) – a type of AI that has the potential to match the versatility and creativity of the human brain.  One of the most awe-inspiring and mysterious migrations in the natural world is currently taking place, stretching from Mexico to the United States and Canada. This incredible spectacle involves millions of monarch butterflies embarking on a monumental aerial journey. Correspondent Anderson Cooper reports from the mountains of Mexico, where the monarchs spent the winter months sheltering in trees before emerging from their slumber to take flight. To learn more about listener data and our privacy practices visit: https://www.audacyinc.com/privacy-policy Learn more about your ad choices. Visit https://podcastchoices.com/adchoices

Listen closely. That's not just paint rolling on a wall. It's artistry. A master painter carefully applying Benjamin Moore Regal Select Eggshell with deftly executed strokes. The roller lightly cradled in his hands, applying just the right amount of paint. It's like hearing poetry in motion. Benjamin Moore, see the love. Step into the freedom of summer with jewelry that reflects who you are and where you're going.

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and they put a blindfold on us, and then we're sent into a gunfight, and we're losing. We are losing. It's moving incredibly fast. Few understand the speed of artificial intelligence like Demis Hassabis. He won a Nobel Prize and showed us what's coming next.

It's reasoning. Yep, definitely, yes. AI, he told us, promises a future of wonder. The end of disease? I think that's within reach. Maybe within the next decade or so. I don't see why not. It's not easy to get to, and it's not easy to see at first,

but then one of the most amazing migration stories in nature reveals itself. Towers of monarch butterflies, orange, twisting, soaring, and one of the most remarkable things we've ever seen. I'm Leslie Stahl. I'm Bill Whitaker. I'm Anderson Cooper. I'm Sharon Alfonsi. I'm John Wertheim.

I'm Cecilia Vega. I'm Scott Pelley. Those stories and more tonight on 60 Minutes. The white chocolate macadamia cream cold brew from Starbucks is made just the way you like it. Handcrafted cold foam topped with

toasted cookie crumble. It's a sweet summer twist on iced coffee. Your cold brew is ready at Starbucks. When I found out my friend got a great deal on a designer dress from Winners, I started wondering, is every fabulous item I see from Winners? Like that woman over there with the Italian leather handbag. Is that from Winners? Ooh, or that beautiful silk skirt.

Did she pay full price? Or those suede sneakers? Or that luggage? Or that trench? Those jeans? That jacket? Those heels? Is anyone paying full price for anything? Stop wondering. Start winning. Winners. Find fabulous for less. Bird flu has been circling the globe for decades. So, the discovery in 2024 that the deadly pathogen had jumped from a wild bird to a cow came as a shock to virus watchers. Now, in just over a year, the virus has ripped through America's dairy herds and poultry flocks. It has jumped to other mammals, including humans. Seventy Americans have caught the virus.

One has died. Long feared as a possible pandemic, doctors and veterinarians fighting the virus told us Biden's government was slow to act, while the Trump administration has now laid off more than a hundred key scientists, all as the virus keeps spreading. At present, we're given a stick, and they put a blindfold on us, and we're sent into a gunfight, and we're losing. We are losing. Veterinarian Dr. Kay Russo told us we are running out of time to stop bird flu. She was called in when the virus H55N1, hit this dairy herd in Colorado

last summer. It cost the farm about $400,000 to treat its sick cattle, most recovered. Some protective gear. But as an added precaution, we suited up to ensure we didn't bring anything onto the farm ourselves. There's no front or back. There's no front or back. It's high fashion. It's real high fashion. It's not clear how bird flu is spread from cow to cow, but milking equipment is a prime suspect.

The virus is thought to linger on the auto milker, waiting for the next cow. Workers here in milking parlors have also fallen sick. So what concerns you the most? The pandemic potential for a virus like this one. And, you know, that is the worst case scenario, right? And ultimately one we want to avoid. I can't say that that's going to happen, but we don't want to play with fire.

It started in Texas. In early 2024, cows were suffering from a mysterious disease. Their fevers spiked. Their milk dried up. They were coughing, drooling, lethargic. Soon, there were more sick cattle in neighboring states. Kay Russo joined a conference call of worried vets to try to figure it out. I started asking questions. What are the birds doing on the farm? And one of the veterinarians replied, well, they're all dead. So they're seeing dead birds on the farms.

Yep. You know, we started to see the cats that were demonstrating neurologic symptoms. And more alarmingly, the workers were complaining of flu-like symptoms. Tests confirmed Russo's worst fears. H5N1 had jumped to cattle for the first time. In past outbreaks, bird flu has often been deadly in people. If you look at cases worldwide of H5 influenza, the mortality rate's 50%. And so we're all kind of, you know, talking to each other, what does this mean? And that was a scary space to be in. Despite the urgency,

Russo and other vets told us the Biden administration was slow to act. It was a month before the U.S. Department of Agriculture required cows to be tested before interstate travel, and 10 months before a raw milk testing program was launched. Today, some states test weekly, some hardly at all. Do we have enough information about how this virus is spreading? I would say today, no. And that comes down to boots on the ground where you have a strike force that comes in the middle of an outbreak and just starts collecting data. Russo told us, at the moment, the virus has the upper hand.

I think it's a numbers game. And the more we let it move unchecked, the more likely we're going to have even a bigger mess on our hands. Poultry farmers have had to kill tens of millions of birds, removing them with trailers and driving egg prices sky high. Now, a new strain of bird flu has been discovered in cattle. It has led to more severe disease in some people. This is a threat that is very significant and very real. And I recognize also this is a moment

where it's easy to sound like an alarmist. What I'm here to tell you is this is a very serious threat to humanity. And the longer we let this persist, the greater the risks are going to be. Dr. Cameron Kahn is an infectious disease physician in Toronto. His company, Blue Dot, was among the first to flag the virus in China that became the COVID pandemic. Kahn told us bird flu is just as concerning. He showed us how fast the virus has spread

among dairy cattle. It seems like almost a wildfire to me. Yeah, absolutely. Now, add in poultry outbreaks. So this is virtually the whole country. Pretty much. Next, Dr. Cameron Kahn showed us a map of all the confirmed human cases of bird flu in the last five years. Most have been in Asia until now.

What you start to see around 2024 is you start to see a case in Texas, and then you start to see this sudden, rapid increase in cases across the country. All over the place. What's happening here is wild birds have infected cows, who have then infected other cows, who have then infected humans. who have then infected other cows, who have then infected humans.

And so there's this complex web of all of these different animal species now passing the virus in different directions. Is this one of those things you have never seen before? The world has never seen this kind of situation. And it's showing us that the virus is capable of adaptation, if you allow it. It will just get better and better

at infecting other mammals, including potentially humans. Most of the confirmed cases in the U.S. have been farm workers. Most had mild symptoms. The one person who died had underlying health conditions. The Centers for Disease Control and Prevention say the virus still poses a low risk to the general public. But Kahn told us many cases are going undetected. Why do you say that? So in a recent study of dairy workers, their blood was tested for antibodies to H5N1,

not looking for the virus, but looking for the immune system's memory of this virus. And it turns out that 7% of them, one out of roughly every 15 workers, actually had antibodies to H5N1. People are not generally getting very sick from this. So what's the reason for all the alarm? Yeah. Influenza is a particularly formidable virus. It is constantly changing.

And the more that we allow it to evolve and adapt by infecting people, I mean, this is kind of Darwinian evolution here, right? It can change in ways that actually make it even more deadly or more easily transmissible or even resist against some of the antiviral medications that we have. Kahn told us every new infection increases the odds bird flu could lead to severe disease, as we saw during COVID. In North America, six people now have ended up in the hospital with bird flu. More worrying, five people had no known exposure to sick animals.

One girl in Mexico died two weeks ago. We are really at risk of this virus evolving into one that has pandemic potential. And the reality is none of us know whether this is next week or next year or never. I don't think it's never. But it may be here far sooner than any of us would like. Many scientists told us vaccines could be our best defense. There is a vaccine for bird flu, but it has not been licensed by the Food and Drug Administration. Moderna has a new one,

but the Trump Administration has paused its final funding. There are vaccines for poultry, too, but they haven't been used because many of America's trading partners will not import vaccinated birds. A glimmer of hope? The USDA's milk testing program. DR. KEITH POLSON, Director, Wisconsin Veterinary Diagnostic Lab, part of the USDA's plan to test raw milk for H5N1. Pasteurization kills the virus, but raw milk can be loaded with it. Is this where you would identify the virus?

Yeah, and it can detect even just one positive cow in a group of a thousand. Forty-five states are now doing some form of testing. Paulson told us it's helped to slow the spread of the virus in some states. When you see the outbreak curve level off or start to decline, do you go like, phew, we dodged one? I don't think we go, phew, until we're deactivated our lab. We're still in outbreak response mode. And while we may have fewer detections, we know that there are still viruses circulating based on all the data from the virologists that we're talking to. And we want to make sure that we catch it fast.

The CDC is trying to ramp up its testing. But there's another problem. Almost half of farm workers are undocumented and may be reluctant to be tested. If we're not testing people, if we're not looking for people who might get it, if we're not looking for evidence of an early cluster of human-to-human transmission, then we're going to miss it. Dr. Angela Rasmussen is an American virologist working in Canada. Rasmussen told us it's not just the number of human cases that is alarming, but that the virus is jumping to more mammals. Every new spillover gives the virus another

chance to evolve and potentially spread person to person. So we are now seeing the viruses spread from birds to cattle and now to foxes, goats, pigs, rats, cats, raccoons. The fact that this virus can infect so many different types of mammals is a huge concern in terms of its ability to infect people. One of your colleagues told us that if this should spiral into a pandemic, this flu could make COVID look like a walk in the park. I agree.

You're scaring me. I'm scared about it myself. I don't sleep very much these days, Bill. Rasmussen was among the scientists given expert briefings by the Biden administration in 2024. She told us Biden's team miscalculated the threat at first. It was some gambling and some wishful thinking, thinking this isn't actually going to be that big of a deal. And it turns out it was a very big deal. Has the Trump administration gotten its arms around this problem?

No, I would say is the short answer. But the other, the longer answer is that I don't actually entirely know what is going on. Why is that? Many of the people who were working on this, at least at CDC, have been fired from the federal government. So the influenza division at CDC has been decimated. And in fact, there is a communications ban that has been put on these federal workers.

What do you think of that? I think it's insane, actually, that I have to have conversations on encrypted messaging apps with my colleagues who I would normally just send emails to. Hundreds of federal scientists and health workers who track bird flu have been laid off. Some may be rehired. The CDC declined to answer our questions, saying it continues to respond to the H5N1 bird flu outbreak. Colorado vet Kay Russo and others told us they feel stymied. The current distrust of science and vaccines is hurting their fight to try to prevent the next pandemic.

I would scorch the earth if this ends up in children deaths. And so as a mother, as a veterinarian, as a scientist, I'm just asking you trust us because I will do everything in my power and there's plenty of folks behind me that will do the same to keep this from getting to that point. The new Mitsubishi Outlander brings out another side of you.

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The PC Insider's World Elite MasterCard. The card for living unlimited. Conditions apply to all benefits. Visit PCFinancial.ca for details. When Demis Hassabis won the Nobel Prize last year, he celebrated by playing poker with a world champion of chess. Hassabis loves a game, which is how he became a pioneer of artificial intelligence. The 48-year-old British scientist is co-founder and CEO of Google's AI powerhouse called DeepMind. We met two years ago when chatbots announced a new age. Now Hassabis and others are chasing what's called artificial general intelligence, a silicon intellect as versatile as a human but with superhuman speed and knowledge. After his Nobel and a knighthood from King Charles,

we hurried back to London to see what's next from a genius who may hold the cards of our future. What's always guided me and the passion I've always had is understanding the world around us. I've always been, since I was a kid, fascinated by the biggest questions. You know, the meaning of life, the nature of consciousness, the nature of reality itself. I've loved reading about all the great scientists who worked on these problems and the philosophers, and I wanted to see if we could advance human knowledge. And for me, my expression of doing that was to build what I think is the ultimate tool for advancing human knowledge, which is AI. We sat down in this room two years ago, and I wonder if AI is moving faster today than you imagined.

It's moving incredibly fast. I think we are on some kind of exponential curve of improvement. Of course, the success of the field in the last few years has attracted even more attention, more resources, more talent. So that's adding to this exponential progress. Exponential curve, in other words, straight up. Yep, straight up and increasing speed of progress. Start. Yeah.

We saw the progress... Hello, Scott. It's nice to see you again. ...in an artificial companion that can see and hear and chat about anything. Early chatbots learned only the Internet. An app called Astra also takes in the world. Do we call her she? It's a good question. I'm not sure we all know the answer yet. Bebo Hsu is product manager for Project Astra, an app in a new generation of chatbots that interpret the world with their own eyes.

We challenged Astra with virtual paintings we chose and showed to Astra for the first time. This is July Hay by Thomas Hart Benton from 1942. How about this one? That is The Virgin of Charity by El Greco. That painting is Automat by Edward Hopper. The person in the painting, what emotion is she exhibiting? The subject in the painting appears pensive and contemplative, her expression suggesting a sense of solitude. Can you create a story around this picture?

It's a chilly evening in the city, a Tuesday perhaps. The woman, perhaps named Eleanor, sits alone in the diner. She is feeling melancholy due to the uncertainty of her future and the weight of unfulfilled dreams. The scene freezes in time, only the flow of ideas moving onward. That line, only the flow of ideas moving onward? I wish I'd written that.

And did we hear a limit to Astra's patience? What was that fictional conversation about? Ah, in the story I imagined, Eleanor and her friend talked about their shared dreams and the challenges of pursuing them. Something about the way you said ah made me wonder if you were getting bored. I apologize if my tone came across that way. My aim is always to engage thoughtfully. And she said, well, I'm sorry if you don't like my tone. Well, you see, what's happening there?

Well, that's interesting. That's, again, a challenge with these systems as they act in the moment with the context that's around them, and that may have never been tested before. He's often surprised because AI programs are sent out on the Internet to learn for themselves. They can return later with unexpected skills. So we have theories about what kinds of capabilities these systems will have. themselves. They can return later with unexpected skills.

So we have theories about what kinds of capabilities these systems will have. That's obviously what we try to build into the architectures. But at the end of the day, how it learns, what it picks up from the data is part of the training of these systems. We don't program that in. It learns like a human being would learn. So new capabilities or properties can emerge from that training situation. You understand how that would worry people. Of course. It's the duality of these types of systems, that they're able to do incredible things, go beyond the things that we're able to design ourselves or understand ourselves.

But, of course, the challenge is making sure that the knowledge databases they create, we understand what's in them. Now, DeepMind is training its AI model called Gemini to not just reveal the world, but to act in it, like booking tickets and shopping online. It's a step toward AGI, Artificial General Intelligence,

with the versatility of a human mind. On track for AGI? In the next five to ten years, I think. And in 2030, you will have what? Well, we'll have a system that really understands everything around you in very nuanced and deep ways and kind of embedded in your everyday life. Embedded like Astra in eyeglasses. What can you tell me about this building I'm looking at? This is the coal drops yard, a shopping and dining district. She

sees what I see. There's a speaker in the earpiece only I can hear. What was it originally before it became shops? The coal drops yard was originally a set of Victorian coal warehouses used to receive and distribute coal across London. Was coal ever a problem for the environment in London? Yes. Coal was a significant source of air pollution in London, particularly during the Industrial Revolution. It occurred to us that the only thing we contributed to this relationship were legs, which will also soon be engineered. I also think another big area will be robotics. I think it will have a breakthrough moment in the next couple of years where we'll have

demonstrations of maybe humanoid robots or other types of robots that can start really doing useful things. For example, researchers Alex Lee and Giulia Vizzani showed us a robot that understands what it sees and reasons its way through vague instructions. Put the blocks whose color is the combination of yellow and blue into the matching color ball. The combination of yellow and blue is green. And it figured that out.

It's reasoning. Yeah, definitely, yes. The toys of Demis Hassabis' childhood weren't blocks, but chess pieces. At 12, he was the number two champion in the world for his age. This passion led to computer chess, video games, and finally, thinking machines. He was born to a Greek Cypriot father and Singaporean mother. Cambridge, MIT, Harvard. He's a computer scientist with a PhD in neuroscience. Because, he reasoned, he had to understand the human brain first.

Are you working on a system today that would be self-aware? I don't think any of today's systems, to me, feel self-aware or conscious in any way. Obviously, everyone needs to make their own decisions by interacting with these chatbots. I think theoretically it's possible. But is self-awareness a goal of yours? Not explicitly, but it may happen implicitly. These systems might acquire some feeling of self-awareness. That is possible.

I think it's important for these systems to understand you, self, and other, and that's probably the beginning of something like self-awareness. But, he says, if a machine becomes self-aware, we may not recognize it. I think there's two reasons we regard each other as conscious. One is that you're exhibiting the behavior of a conscious being, very similar to my behavior. But the second thing is you're running on the same substrate. We're made of the same carbon matter with our squishy brains. Now, obviously, with machines, they're running on silicon. So even if they exhibit the same behaviors, and even if they

say the same things, it doesn't necessarily mean that this sensation of consciousness that we have is the same thing they all have. Has an AI engine ever asked a question that was unanticipated? Not so far that I've experienced. And I think that's getting at the idea of what's still missing from these systems. They still can't really yet go beyond asking a new novel question or a new novel conjecture or coming up with a new hypothesis that has not been thought of before. They don't have curiosity. No, they don't have curiosity, and they're probably lacking a little bit in what we would call imagination and intuition. But they will have greater imagination, he says, and soon.

I think actually in the next maybe five to ten years, I think we'll have systems that are capable of not only solving an important problem or conjecture in science, but coming up with it in the first place. Solving an important problem won Hassabis a Nobel Prize last year. He and colleague John Jumper created an AI model that deciphered the structure of proteins. Proteins are the basic building blocks of life. So everything in biology, everything in your body depends on proteins. You know, your neurons firing, your muscle fibers twitching, it's all mediated by proteins. But 3D protein structures like this are so complex, less than 1% were known. Mapping each one used to take years. DeepMind's AI model did 200 million in one year. Now,

Hassabis has AI blazing through solutions to drug development. So on average, it takes, you know, 10 years and billions of dollars to design just one drug. We could maybe reduce that down from years to maybe months or maybe even weeks, which sounds incredible today, but that's also what people used to think about protein structures. It would revolutionize human health, and I think one day maybe we can cure all disease with the help of AI. The end of disease?

I think that's within reach. Maybe within the next decade or so. I don't see why not. Demis Hassabis told us AI could lead to what he calls radical abundance, the elimination of scarcity. But he also worries about risk. There's two worries that I worry about. One is that bad actors,

human users of these systems, repurpose these systems for harmful ends. Then the second thing is the AI systems themselves, as they become more autonomous and more powerful, can we make sure that we can keep control of the systems, that they're aligned with our values, they're doing what we want, that benefits

society, and they stay on guardrails. Guardrails are safety limits built into the system. And I wonder if the race for AI dominance is a race to the bottom for safety. So that's one of my big worries, actually, is that, of course, all of this energy and racing and resources is great for progress,

but it might incentivize certain actors in that to cut corners. And one of the corners that can be shortcut would be safety and responsibility. So the question is, is how can we coordinate more, you know, as leading players, but also nation states even. I think this is an international thing. AI is going to affect every country, everybody in the world.

So I think it's really important that the world and the international community has a say in this. Can you teach an AI agent morality? I think you can. They learn by demonstration. They learn by teaching. And I think that's one of the things we have to do with these systems is to give them a value system and a guidance and some guardrails around that, much in the way that you would teach a child.

Google DeepMind is in a race with dozens of others striving for artificial general intelligence, so human that you can't tell the difference. Which made us think about Demis Hassaba signing the Nobel Book of Laureates. When does a machine sign for the first time? And after that, will humans ever sign it again? I think in the next steps, it's going to be these amazing tools that enhance our almost every endeavor we do as humans. And then beyond that, when AGI arrives, you know, I think it's going to change pretty much everything about the way we do things. And it's almost, you know,

I think we need new great philosophers to come about, hopefully in the next five, 10 years, to understand the implications of this. Meet Tim's new Oreo Mocha Ice ice caps with Oreo in every sip. Perfect for listening to the A side or B side or bull side. Order yours on the Tim's app today at participating restaurants in Canada for a limited time. When does fast grocery delivery through Instacart matter most? When your famous grainy mustard potato salad isn't so famous without the grainy mustard.

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right now from Mexico to the United States. Tens of millions of monarch butterflies are on an epic aerial journey home. They've spent the winter hanging out in trees in a forest on a remote mountain in Mexico, resting up after flying all the way from Canada in the northern U.S. where they were born. It's believed monarchs have been making this journey for thousands of years, but there's a lot fewer of them than there used to be. The population in Mexico has declined 70 percent in the last 30 years. We arrived there in February, just in time to watch the monarchs emerge from their slumber and begin to take flight. The monarchs come to these mountains in Michoacan in central Mexico, starting in late October.

Do you still get excited going up to see them? Every time. There's no substitute. One of our guides, Jorge Rickards, is the director of the non-profit Rural Wildlife Fund in Mexico. We're going to leave the horses, walk a little bit, very, very carefully and very quietly so we won't disturb the butterflies. The monarchs roost in patches of fir and pine trees 11,000 feet up.

There are some 66 million of them here, but it's hard to see them at first. There are what appear to be clumps of dead leaves hanging from sagging branches. But those are butterflies, tens of thousands of them clustered together in trees all around. There's so many of them on the branches of the trees that the branches are all pointing toward the ground.

Imagine, imagine the likeness of a butterfly, and there are so many of them here that they actually bend the trees. And they like the firs because they have so many little leaves or spicules. So there's lots of surface to cling on to. The monarchs earn a kind of hibernation. On the way here, they've fattened up on nectar, which helps them survive and rest through the long winter months. The climate on this mountain is ideal.

The canopy of trees protects the butterflies from storms, and though the air is cool, it's relatively humid, so they stay hydrated. The clusters are so drab when you're looking at them because they have their wings closed. In many butterflies, the underside is drab or less lightly colored, and that happens in nature a lot. So it's not very inviting. It wouldn't be inviting to a predator. Why are we whispering?

They are very sensitive to sound. They are also sensitive to CO2. So the less we talk, the better. They relate that with a predator. As other mammals might be. So they can sense like a mouse breathing. Or a bird. A bird breathing.

That is right. On the forest floor all around us, monarchs litter the ground. But most are not dead. They've just fallen from trees during the night, and their muscles are too cold for them to fly. Cup them in your hands. You can revive them with your breath. The muscles are too cold for them to fly. Cup them in your hands, you can revive them with your breath. So they need a certain temperature

to get their wing muscles back. They are very, very vulnerable when they're on the floor. And the birds know that, and the mice know that. That's almost ready. There you go. Come on, little buddy. Maybe a little more. There you go. There, he likes you.

Wow. When the sun begins to hit the trees, flashes of orange appear. The monarchs are warming and slowly opening their wings. Really as the day warms up, we're going to see more activity. Court Whalen has been bringing tour groups here and photographing monarchs for more than 20 years. He shows us a spot where some butterflies have taken flight. Then, after a few minutes, suddenly, the air is filled with them.

This is extraordinary. This is it. This is what it's all about. This is, uh, nature knows when to put on a show, huh? And how to put on a show. Why have they all now just suddenly taken off? So it's a warm day. We're getting a lot of sunlight.

So we're just ramping up, ramping up. I mean, what's insane is it's not just over here, it's over there, it's over there. I mean. It's extraordinary. But yeah, it's all the heat and it's all the sun. You can actually hear the sound of butterfly wings. Yeah.

Let's just be quiet for a second. Look at that, look at that up there. Oh my gosh. Whoa. This is about as good as it possibly gets. It's like a snow globe of monarchs. You got a butterfly on you. Oh, there we go. It's still something of a mystery how these monarchs manage to get here.

Most only live about a month. They spend their short lives eating and mating, and females lay eggs. But in late summer and early fall, what's called a supergeneration of monarchs appear. Hatched as caterpillars, they transform into chrysalises. And then, after a week or two, emerge as butterflies. And that's when they do something extraordinary. With winter coming, they sense the shorter days and changing temperatures and suppress

a key reproductive hormone, a process called diapause, which helps them conserve their energy and live up to nine months, nine times longer than most monarchs. It's crazy that there's this super generation of monarchs that can make it all the way and then the rest die off after a month. What is amazing is how they detonate this process of not developing sexual organs, but using that energy for the flight. Monarchs born west of the Rockies stay there and migrate shorter distances. It's this super generation, born in Canada and east of

the Rockies in the northern United States, that flies to Mexico. Hundreds of millions of them join up on a journey of some 3,000 miles, which can take them three months or longer. To help them find their way, monarchs have circadian clocks in their antennae and navigate using internal compasses that respond to the position of the sun and the earth's magnetic field. Why are they coming here? Well, that's a big mystery. Maybe it's a prehistoric route. Maybe it was determined by geographical conditions in terms of topography. Maybe it had to do with climate.

You're talking about multiple generations who all have this exact same instinct and know where to go and all go to the exact same spot. That's one of the most magical things that can happen in the natural world. How do they know? The monarchs were discovered by researchers on this mountain range in 1975,

and the Mexican government declared the area a Federal Reserve 11 years later. But for decades, illegal logging threatened the butterflies' roosting spots, which once covered as much as 45 acres. It's now down to four and a half. World Wildlife Fund has spent years trying to combat the destruction, assessing the health of the forest, measuring the size of butterfly colonies, and planting trees. They've also worked with local communities and indigenous groups to protect the land and help them profit from tourism.

The good news is the forest is rebounding. Because it's just so unusual to see this. from tourism. The good news is the forest is rebounding. Because it's just so unusual to see this. It's like almost an optical illusion, because everything's beating at this weird frequency. It's like the whole world is kind of pulsing. So what are they doing here? Yeah, so this is kind of a classic mud puddling

of monarch butterflies. Mud puddling? Yeah, mud puddling. It's a real scientific term. So they're mainly after hydration, but butterflies are known to need some trace elements like salts and whatnot. And it doesn't look like much, but just this little bit of water in this mud puddle is enough for them to get some water. And then what will happen is they'll return to the roost before evening. After about four months in Mexico, this super generation of monarchs are near the end of their long life cycle. They're finally ready to mate and migrate north to lay their eggs. They'll die

before they can make it back to where they were born, and their offspring might not live long enough to get there either, but future generations will. And there's an army of people trying to help them. In Kansas, volunteers come out to catch and tag monarchs so scientists can track their migration. Good job, babe. They're recruited by Chip Taylor, an 87-year-old ecologist who's been fascinated by monarchs since he was a child. There's over 100,000 species of butterflies and moths, but pretty much the only one people know are monarchs. What is it about monarch butterflies?

Well, monarchs have got charisma. Wait a minute. Monarch butterflies have charisma? Well, yeah, they have charisma because they are accessible, they're large, they're beautiful, they're slow. You can catch them. It involves Canada, it involves Mexico. Taylor founded a non-profit called Monarch Watch at the University of Kansas 30 years ago.

Nice. And so far, it's helped tag more than 2 million of them. How do you tag a butterfly that's so delicate? This is a rough butterfly, and it has to go thousands of miles. So it's a pretty tough butterfly. It's resilient. Yeah, it's resilient. But that resilience is being tested.

Monarchs returning to the U.S. need milkweed plants to lay their eggs on. It's the only source of food their newly born caterpillars will eat. But milkweed is now hard to find. It's been virtually eradicated on agricultural land because of genetically modified corn and soybean crops that allow for mass spraying of herbicides. Monarch Watch encourages people to plant milkweed in their gardens and on public land,

creating what they call monarch way stations. 50,000 of them have been planted so far. In Mexico, those efforts have gotten noticed. They are taking water. Eduardo Rendon, head of World Wildlife Fund's Monarch Butterfly Program, showed us a tag he recently found. So this is one of the tags from Monarch Watch from Chip Taylor. Exactly. I find maybe 12 meters from over here.

Yeah, I was measuring the colony and then I see the ground and I find this tag. But it's the only way that we can prove that monarchs from the United States and Canada come here to overwinter. Less than 20% of the monarchs that head out on this miraculous migration actually make it to the mountains of Michoacán. Scientists say worsening storms and rising temperatures kill off many, though this past year the number of monarchs that survived the trip nearly doubled. It was particularly welcome news in Mexico, where the butterflies' arrival in late October coincides with a deeply spiritual celebration, what's known as the Day of the Dead. That's when many here believe the souls of family and friends who died returned to visit their loved ones.

And so that's why the butterflies are returning as well. Local people believe that the monarchs are the returning spirits of... That is correct. ...of the dead. That is correct, yes. So who knows, maybe we are actually, you are reviving, you're helping someone's ancestor fly back. Yes, indeed. So it's very magical.

Now, the last minute of 60 Minutes. Today in Paris, Easter Sunday Mass was celebrated in the Cathedral of Notre Dame for the first time in six years. It was just five days before Easter, 2019, that a devastating fire swept through the great church. French President Emmanuel Macron pledged the next day to have Notre Dame restored and reopened within five years. And when we got a sneak peek inside last November, just days before Macron kept that promise, we witnessed a true resurrection. In the first month after Notre Dame's bells began to ring again, 800,000 visitors came through, and they keep coming to see this modern miracle. An average of 29,000 people are visiting every day. That's about 5,000 more than came before the fire. I'm Bill Whitaker. We'll be back next week with another edition of 60 Minutes.

Happy Easter and Passover.