On April 26, 1986, the Soviet Union’s Chornobyl Power Complex nuclear reactor 4 exploded, releasing a massive amount of highly radioactive material. People living near the power plant were forced to evacuate, and the area was deemed uninhabitable. But today, many animals — some the descendants of pets left behind — have made this region their home. In this episode, we chat with researchers who have spent a lot of time in the Chornobyl Exclusion Zone studying the animals that live there, trying to understand how constant low levels of radiation impact their health. What they’re learning could inform plans to repopulate areas that suffered past nuclear disasters, including Fukushima, and help with the development of methods that protect astronauts from radioactivity in space.
Transcript of this Episode
Sam: On April 26, 1986, the Soviet Union’s Chornobyl Power Complex nuclear reactor 4 exploded. Ironically enough, they were doing a safety test on that particular reactor, checking to see if they could keep the safety systems running during a power loss until the backup generator kicked in. The test was of course not successful.
Deboki: The explosion released a massive amount of highly radioactive material that affected a large part of Eastern Europe and probably spread even further. People living near the power plant were forced to evacuate, and the area was deemed uninhabitable. But today, many animals have made or continue to make this region their home.
Welcome to Tiny Matters, a science podcast about the little things that have a big impact on our society, past and present. I’m Deboki Chakravarti and I’m joined by my co-host Sam Jones. In today’s episode, Sam and I are going to hear from people who’ve spent a lot of time in the Chornobyl Exclusion Zone working with and studying the wildlife that appears to be thriving there.
Jennifer Betz: You cannot fly into Ukraine anymore, so you have to fly to Poland, take an 18 hour train ride with all of our supplies, get to Kyiv, then get picked up in Kyiv and transported to Chornobyl. So it's quite the ordeal to get there and get back.
Sam: That’s Jennifer Betz, the Veterinary Medical Director of the Clean Futures Fund.
Jennifer Betz: When you get to Dytiatky, there's a huge checkpoint there, and it's governed by military and radiation control. They search your car, you get out, they check your paperwork before you're allowed into this area. Once you get into this area, then you drive another mile of just woods and then you'll come to another checkpoint. You have to cross through that checkpoint. And then you'll get into Chornobyl Town.
Sam: Jennifer has been visiting Chornobyl in northern Ukraine a couple times a year since 2018.
Jennifer Betz: And then you leave that area and you drive more wooded areas to get to the nuclear power plant. You'll pass through what they call the Red Forest. The Red Forest is the area after the disaster where a lot of the fallout fell and the trees’ leaves had all turned red. And so that's what they call it the Red Forest. And since then, those trees have been all cut down.
Deboki: Sam, I assume you’re kind of like me where you know about Chornobyl and that it was this huge horrifying event. But it’s easy to lose track of some of the specifics of just what that looked like. After the meltdown of one of Chornobyl’s four nuclear reactors, the reactor’s core continued to burn for ten days before it could be contained, raining highly radioactive material on parts of Ukraine, Belarus, and Russia. And more than 700 miles away in Stockholm, Sweden, nuclear facilities detected elevated levels of radiation in the air. The Soviet government evacuated 350,000 people living within a thirty-kilometer radius of the power plant, establishing what is now known as the Exclusion Zone.
And when I hear “exclusion zone,” my brain conjures up an empty place that doesn’t have a lot going on. But that’s not the case.
Jennifer Betz: When you come to the power plant, all of a sudden you come into this big area, you see the giant arch that's covering the blown-up reactor number four, and you see a lot of the water towers, cooling towers, a lot of security fencing, and there's just this massive huge industrial site that you see. You see dogs running around everywhere, a lot of people working, and big, huge cooling ponds with the giant wels catfish that are in there. It's a pretty remarkable place to see.
Sam: There are people working in Chornobyl, even though the reactors are no longer producing electricity.
Jennifer Betz: With nuclear reactors, you have to do something with the spent fuel, and that's something that they're going to be dealing with for years and years and years. So there's always going to be activity in this area. You can't just shut down a power plant and say, okay, see you later.
Sam: When the original residents were evacuating Chornobyl, they thought they would be gone for only a few days and they left their pets behind. Unfortunately, that turned out to not be the case. But the descendents of those dogs now live as packs of feral dogs around the area. Jennifer leads a program called Dogs of Chornobyl, working with other volunteers to care for them.
Jennifer Betz: So a lot of them are larger-breed dogs, they’re kind of a shepherd type dog, shepherd-cross have really big, huge ears. And that's one of the things that makes them unique is that they have these ginormous ears.
Sam: Obviously as a dog-lover, my first instinct would be to pet the dogs. But while most are friendly, they’re also feral and many are scared of humans. It makes sense when you remember that these dogs haven’t had much human interaction for generations. Jennifer told us that the majority of the dogs will only come within six to 10 feet of people. But some do go on to form friendships with the humans they meet.
Jennifer Betz: You get to know 'em. Some of 'em become your favorites. And I had one before the war, Beauty. And she would always come and spend the night with me in the laboratory every time we went back. But when I went back after the war, I couldn't find her.
Deboki: Although she and others have developed these nice relationships with the dogs, having them wandering around an industrial site is a challenge. For three decades, the dogs lived off food scraps and handouts from the power plant cafeteria. And they reproduced, reaching a population of over a thousand in 2017. In some cases, Jennifer told us that dogs have bitten people on the site. But this is also a dangerous place for dogs to live, and for a time, their life expectancies were very short.
Jennifer Betz: A lot of them would die from being hit by cars, from dog fights, from diseases, distemper, parvo, things like that. And so since we started going in there, we were vaccinating all of these dogs for rabies, for distemper, providing medical care. And then they started to live longer.
Deboki: Jennifer says workers on site continuously monitor the population and are in constant contact with her, giving updates on how the dogs are doing.
And the Dogs of Chornobyl volunteers have been working hard to spay or neuter every single dog living on the nuclear site. So while they can continue to live hopefully happy, healthy lives, at the same time the dog population will dwindle and fade away. It has taken several trips, and some collaboration with reactor workers who know the dogs well. But the team is approaching their goal of no new puppies being born in the area.
Jennifer Betz: And now they're down to less than 300 in the whole 30-kilometer exclusion zone. What we're doing now is more of a maintenance phase when we do have a litter pop up here and there, because you can't catch 'em all. We do have some litters that pop up, and then I will go over there with a very small crew and we'll catch those dogs and then spay and neuter and vaccinate them.
I'm sorry, can you hear the dog barking? I'm sorry. She's a puppy and she… [Sam laughs]
Sam: I’m a dog owner… I get it. I mean, how many times have my dogs interrupted a call? And by the way, the puppy in the background of our call with Jennifer was not a Chornobyl dog. We asked her if people could adopt dogs living at the Exclusion Zone because of course that’s where my brain goes, but you cannot. If you want to help, you can donate to the Clean Futures Fund or you can buy a sticker with a QR code that you can use to check for updates about specific dogs who live in the Exclusion Zone. I’ll put a link in the episode description.
But I digress. Let’s get back to Jennifer. We talked with her a week after she returned from her most recent trip to Ukraine, and she told us about some of the special challenges that come with working in what is now a war zone.
Jennifer Betz: It's not easy to get in. There's a lot of approvals we have to get. But since we've been going in there regularly, since the start of the war, we have access to get in there when a lot of people do not.
Deboki: She also told us about the daily work that her team does while there at Chornobyl. To capture the dogs, the vets usually have to tranquilize them with blow darts.
Jennifer Betz: And then they're brought back to our temporary facility that we have set up in one of the abandoned buildings. And we frisk them for radiation before we deal with them. And if they're clean, we bring them back into the surgery area. If they're not clean, we usually have to wash them or shave the fur to get the contaminants off so that we don't become contaminated or touch that because we’re touching them.
And then during that time, we would spay and neuter them. We would microchip 'em, vaccinate them, deworm them during recovery. Once they're awake, we put ear tags in there. On the ear tags, they're fitted with dosimeters to track the radiation levels that they're getting exposed to.
Deboki: I want to dive deeper on this concept of radiation. I feel like it’s a word that gets thrown around alot, but it’s not always clear what it means. Radiation is energy that travels through space, like light from the sun. Low-energy radiation, like radio waves, can pass through our bodies without having much of an effect. But types of radiation with very high energy can damage our tissues.
Sam: The smallest unit of radiation is called a photon, which you can think of as a tiny energy particle. X-ray and gamma-ray photons are so high in energy that when an electron in a molecule absorbs one of them, that electron can leave the molecule, turning the molecule into an ion. That’s why X-rays and gamma rays are classified as “ionizing radiation.” A large dose of ionizing radiation can cause burns or severe illness. It can also cause brain damage in developing fetuses.
Germán Orizaola: Ionizing radiation is the kind of radiation that is associated to radioactive substances. The kind of radiation you have in a nuclear power plant, for example, or nuclear bomb.
Sam: That’s Germán Orizaola, an associate professor in Zoology at the University of Oviedo in Spain. He studies wild animals in the Chornobyl Exclusion Zone. As he explained to us, ionizing radiation is a problem because it can physically break DNA strands. And as the DNA gets repaired, sometimes mistakes can happen, leading to mutations.
Deboki: Low levels of ionizing radiation won’t burn you or cause your organs to shut down. But if you’re exposed over a long period of time, the DNA mutations that accumulate can lead to cancer. But, to be clear, this risk is not limited to nuclear disaster zones like Chornobyl.
Germán Orizaola: We are always exposed to ionizing radiation. It's the same radiation that we get from cosmic rays that just are constantly arriving to the earth. And also from some of the materials that we have on the ground. We are always exposed to really low radiation levels.
Deboki: Certain natural materials contain radioactive atoms. These atoms are unstable, which means that every now and then, one will decay — or break apart — emitting high-energy particles. The two most common of these emitted particles are called alpha and beta particles.
Sam: And cosmic rays consist of high-energy particles that stream out of the sun. They mostly include protons, alpha particles, and beta particles. While Earth’s atmosphere and magnetic field protect us from most of these, we get an extra dose of cosmic rays anytime we travel by airplane, since there’s less of that protective layer between us and the sun.
But surely, you’d expect that someone working in the Exclusion Zone would be exposed to a lot more radiation than someone on a plane, right?
Germán Orizaola: We worked for two weeks in a row, we entered into the exclusion zone into the area, and we were there for two weeks working there, sleeping there, eating there, everything. So we accumulate as much radiation as you accumulate in two flights from U.S. to Europe, back and forth.
Sam: I kind of found that shocking. It’s a lot less than I thought.
Deboki: Yeah, I would not have expected that at all.
Sam: But, at one point, Chornobyl was an extremely dangerous place to visit. The reactor explosion and subsequent fire in 1986 released 400 times more radiation than the nuclear bomb that was dropped on Hiroshima. Twenty-eight people working at the plant or responding to the accident died by acute radiation exposure, which can involve skin burns, vomiting, and organ failure. Thousands of people living in the surrounding area developed thyroid cancer from iodine-131 contamination in the air, and 15 people died from it.
Deboki: But Germán told us that right now, only about 10% of the radiation that was released at the time of the accident is still there. And that’s because the most radioactive materials are also the quickest to decay.
Germán Orizaola: So we have, for example, iodine that is really nasty, it’s the one that is linked to thyroid cancer, for example. It disappears in weeks. The accident happened in end of April, 1986. By the summer or 1986, there were no iodine anymore in Chornobyl.
Deboki: Other isotopes, like cesium-137 and strontium-90, decay much, much more slowly, so there’s still some of them around. Which means that, even though the radiation hazards of Chornobyl are not zero, the animals that live there don’t seem to suffer any acute effects.
Jennifer Betz: None of them have three legs and three heads. And you hear all these things about Chornobyl that they're radioactive or they're glowing. None of that is true.
Sam: In fact, they don’t even seem to have higher rates of cancer than other dogs, although the team will continue to monitor their health and radiation exposure.
Jennifer’s team works with researchers in genetics and evolutionary biology who analyze blood samples taken from the dogs. They found that those living inside the Exclusion Zone are “genetically distinct” from other dog populations. All this means is that there is very little cross-breeding between dogs inside and outside the zone. The scientists plan to use this genetic information as a baseline to observe the effects of continuous radiation exposure on the dogs. But from a veterinary perspective…
Jennifer Betz: They all seem to be very, very healthy. There's not any overt signs of anything, tumors or anything like that.
Sam: What’s especially exciting is that dogs are not the only animals making the Chornobyl Exclusion Zone their home.
Jennifer Betz: I see a lot of moose, a lot of foxes, raccoon dogs. There's a lot of wildlife that has returned to the area, and mostly because of there's no hunting allowed in this region.
Sam: The wild animals are Germán’s area of research.
Germán Orizaola: Right now it’s an area with the highest density of wolves in the continent. Brown bears that were extinct in the area because they were hunted to extinction, they are back in the area. You have beavers, you have elk and deer and lynxes. Whatever species is most protected and endangered in Eastern Europe you have it there and you have it in really big numbers. So actually this area that was supposed to be a wasteland has transformed probably into the best nature preserve in Europe.
Sam: We asked about the reasons that wildlife are doing so well there.
Germán Orizaola: So big animals by definition need big spaces. And what nature often don't have, especially here in Europe, is big spaces.So what you have in Chornobyl is a really, really big area. No humans, free from predators, plenty of food for them.
Deboki: It turns out that the pro of having almost no humans around vastly outweighs the con of low-level radiation. But, Germán has found an interesting example of adaptation to that radiation in the Eastern tree frogs that he studies.
Germán Orizaola: I always remember, first night that I was in Chornobyl, I was in a pond that is really close to the damaged reactor. You could see it from the pond. It was during the night, I was hearing one of those frogs, tried to catch it and I didn't see it. The frog’s supposed to be bright green. It was impossible to see that frog until I realized it was black, completely black. And from then on, all those years that we have been working there, we realized that frogs in Chornobyl, especially in the areas that experienced the higher contamination at the time of the accident, are way darker. Not necessarily black, there are quite a few black or that are green, but they are not this kind of bright green. They are dark green.
Deboki: The frogs that are darker are producing more melanin.
Germán Orizaola: And actually you think about it, melanin even in our skin is a pigment that protects us from radiation — from sun radiation, UV radiation. Our question was, can melanin be also protecting those frogs from ionizing radiation?
Deboki: Remember, ionizing radiation is the high energy radiation found in X-rays or, in this case, a nuclear power plant. And it’s not just these frogs who adapted to have black coloring in high-radiation environments. For example, there are black fungi growing in the damaged reactor, as well as around the International Space Station. Space has intense radiation, which we’ll get to in just a minute.
Germán Orizaola: So it looks like that melanin is doing something, we still don't know exactly what it does. So that's something that we are working on now in the lab.
Sam: Germán’s research group studies frogs and beetles to see if the darker coloring protects these creatures from radiation exposure.
Germán Orizaola: It looks like it reduces both the physical damage of radiation and also the indirect damage of radiation that is through free radicals. Radiation creates free radicals in our cells. Melanin actually looks like it reduces the effects of those free radicals.
Sam: This is a clear case of evolution by natural selection. If black frogs were better-equipped to survive the intense radiation of the nuclear meltdown, they were more likely than the green ones to live long enough to reproduce and pass on their genes. But since frogs don’t move around much in their life cycles, this only applies to ones living near the reactor.
Germán Orizaola: As soon as you move out of the area and go to areas that are not contaminated, you suddenly are back to those bright green frogs.
Deboki: Germán’s team has checked several different health markers for Eastern tree frogs inside and outside of the Exclusion one: their hormone levels, their rate of aging, their lifespan, and their liver and kidney function.
Germán Orizaola: Everything looks normal. The only thing we have found that is really different is the color of those frogs.
Deboki: And it makes sense that they look normal because the radiation those frogs are experiencing now are below the levels considered dangerous for a frog.
Sam: Recently, the group has been particularly interested in a large mammal once at the brink of extinction: Przewalski’s horses.
Przewalski’s horses are known as takhi in Mongolia, where their name means “spirit.” They’re considered too wild to tame, and they don’t do well in captivity. But their numbers dwindled in the mid-twentieth century due to a variety of human pressures. All the takhi alive today are descended from twelve individuals bred at zoos in Europe. Today, their population is back up to 2,000, with many herds reintroduced to the wild.
Germán Orizaola: A few of those horses were released in Chornobyl in 1998, so 12 years after the accident. And for me they are the really key species to study there because they never experienced a really acute stage of the accident, the really, really high levels. So for me it's the same as if humans could have been out of the area for a few years, the years with really high radiation levels, and then back.
Sam: Studying these horses could help us learn about the safety of repopulating areas affected by nuclear accidents, like Chornobyl and Fukushima. But it can also teach us about the safety of sending people to the final frontier of space.
Germán Orizaola: So one of the big problems to space exploration is radiation. Radiation levels are really high. If we understand how radiation affects the body of an organism, if we understand how can we protect those bodies, for example, through melanin somehow, that could help space exploration.
Sam: Germán’s studies of the Przewalski’s horses were interrupted by the COVID-19 pandemic and then the current war. But they still have good information on the size and distribution of the herds.
Germán Orizaola: And actually they're doing pretty well. There were 30 horses released in 1998. They were kind of released in not the best way, so half died. So from 15 more or less that remain, now we are approaching 200 horses. So just by numbers, they're doing pretty well.
Deboki: Luckily for the horses, and the bears and wolves, Chornobyl is now a designated nature preserve.
Germán Orizaola: Just by moving humans out, you transform an area into a sort of paradise for wolves and bears and whatever. I think it tells a big lesson for conservation in other areas. It doesn't matter if it's in the US or it is Europe, you need to give them space.
Deboki: Germán also sees the Chornobyl site as a reminder of history — one that is important to keep alive.
Germán Orizaola: I think the key would be preserving Chornobyl as a memory place. We cannot forget what happened there. And the people who were affected.
Deboki: The accident at Chornobyl exposed major fundamental flaws in a reactor design used in Eastern Europe at the time — a design not used in other parts of the world. The explosion was caused by a combination of these design flaws along with sloppy oversight and a total disregard for protocol by some of the higher-ranking people in charge.
Sam: It had such a large impact on not just the region but the world that it is believed to have contributed to the fall of the Soviet Union five years later. Thankfully, since then, improved monitoring of nuclear facilities and global communication on acceptable standards have made a repeat disaster nearly impossible.
But as we can see from the work Jennifer and Germán are doing, the accident has continued to affect the area, and we’re really still in the early days of understanding how wildlife has been impacted.
Deboki: I know, I wonder if we did this episode again in 20 years, what it would be like. What will the dog population look like? What will the frogs look like? How about the horses? But I guess those are questions for future scientists and science podcasters to answer.
Sam: Let's hop into the tiny show-and-tells. I can't remember, but I'll just go.
Deboki: No, go for it.
Sam: So, Deboki, I want to tell you about how a Mastodon jaw was found in the backyard of a house in New York.
Deboki: Fun.
Sam: Very fun. And actually a piece of toe bone and a rib fragment were also found.
Deboki: Also from the mastodon, right? Not like a piece-
Sam: Yes.
Deboki: It's like a mastodon and a person.
Sam: Oh my gosh. My understanding is that it's from a mastodon. This could get a lot darker. So they roamed the earth from around 4 million years ago to 11,000 years ago.
Deboki: That's a pretty long time span.
Sam: They were here for a while. And so they died off about 7,000 years before the woolly mammoths did.
So woolly mammoth, more recent. So mastodons, they're distant relatives of today's elephants about the same size as most species today, eight to 10 feet tall, around six tons weight-wise. But they had flatter skulls. It's so funny. I was sort of looking at a side-by-side comparison, and elephants have these pretty pointy heads, and the mastodon, it really looks like you just kind of smooshed the head down. It's very interesting. And in the case of the mastodon, a mix of climate change and overhunting by early humans is probably what led to their extinction, which is a common trend.
So back to 2024, New York. Jaw, piece of toe bone, rib fragment, they're excavated by teams from the New York State Museum and the State University of New York Orange after a homeowner in Orange County, which is about 60 miles north of New York City, noticed, and this is a quote from them, "Two unusual teeth concealed by plant fronds," which is just fascinating. And these are not small teeth.
I guess this is the first time in 11 years that part of a mastodon skeleton has been found in New York. And when I read that I was, like, only 11, how often is this happening? And I guess more than 150 Mastodon fossils have been found in New York State. And apparently Orange County in New York is a hotspot for finding mastodon skeletons had no idea.
So now the jaw and bone fragments, they're being carbon dated. They're trying to do a dietary reconstruction, I guess, with the bones, which is really cool, trying to figure out what did this animal eat? And we did talk about some of this stuff in episode 72 of Tiny Matters, as it relates to woolly mammoth migration and the megalodon's diet. So there's a lot of really cool stuff you can learn, especially from teeth. And tusks also include teeth, PS.
So apparently the New York State Museum is going to showcase the jaw next year. Actually, I say next year, but this episode is coming out January 8th, so this year, 2025. And so when I was reading about this, it also made me think about what you would do if you found something like that on your property. I don't actually know what the laws are when it comes to that kind of thing, but I would imagine you'd want to donate it to a museum or something. But in the CNN article that I found about this, the resident was quoted as saying, "I'm thrilled that our property has yielded such an important find for the scientific community," which I thought was so cool. So if you find a really cool thing in your backyard, that's how to do it.
Deboki: Yeah, I would love to.. Is there a mastodon hotline or the paleontologist... Also, it must be so cool to be a paleontologist and to be like, ah, my species. Do you have to resist the urge to go knocking on doors in Orange County, New York to be like, hey, can you just double check that there's a mastodon? We just really want to know. Yeah, there must have just been a herd of mastodons out there that were just like, this is where we live.
Sam: They all must have died there. It must have been, because that's a lot of skeletons to dig up. I just thought this was just very cool, and fun, and you never know what's in your backyard.
Deboki: Yeah, that's really fun. I have a tiny show-and-tell too, because that's what we do. So mine is about how moths listen to plants.
So I don't think of plants as being particularly loud, but that's just because I'm not good at listening to them. Because just like anybody else, plants can do some whining. If life gets stressful for a plant, if they're dehydrated or something's just not right, they'll apparently let out these ultrasonic clicks, and we can't hear these clicks, but insects can. And so some researchers were curious like, huh, if the insects can hear these sounds, are they also able to use them to make choices? And so they were working with the species of moth called the Egyptian cotton leaf worm, and they wanted to see if the sounds produced by the plants affect where female leaf worms lay their eggs. And so starting off, they establish that, yes, the leaf worms do prefer to lay their eggs on a healthy plant, which makes sense because you want your larva, when they hatch, you want them to have food. And so if they're laid on a healthy plant, that food is right there and it's available.
But then they did something kind of neat. They took two hydrated tomato plants, so they were both healthy next to one of the hydrated plants. They took the sounds from an unhealthy plant and just set up a little recording there so that the moths could hear it. And they found that the moths prefer to lay their eggs on the quieter plant, which suggests that the moths prefer the plant not sending out any distress signals.
Sam: Interesting.
Deboki: Yeah. So I just thought that was really cool. It is just always fascinating realizing all of the signals that are happening around us in nature that, some of them we pick up on and we take it for granted. And then also, I think when you hear about the ones that you don't pick up on, you're like, man, There's just so much more going on than we know.
Sam: It makes me think of Ed Yong's book, An Immense World, the ways that all of the creatures and plants, and I don't remember him actually writing about plants. Maybe he did, and I'm just not remembering. I think it was more animal-focused
Deboki: But there must've been something about how animals, yeah.
Sam: Yeah. There's probably something in there that I'm just not remembering. There was so much, so much. But yeah, I think as humans, we're obviously, we're very human centric and we think about how we communicate and how we hear and all of these things. And there's so many different worlds of seeing and feeling and hearing that we just are never going to be able to tap into.
Deboki: Totally. Thanks for tuning in to this week’s episode of Tiny Matters, a podcast brought to you by the American Chemical Society and produced by Multitude. This week’s script was written by Anne Hylden and was edited by me, Michael David, and Sam Jones, who is also our exec producer. It was fact-checked by Michelle Boucher. The Tiny Matters theme and episode sound design is by Michael Simonelli and the Charts & Leisure team.
Sam: Thanks so much to Germán Orizaola and Jennifer Betz for joining us. A reminder that we have a newsletter! Sign up for updates on new Tiny Matters episodes, video clips from interviews, a sneak peek at upcoming episodes, and other science content we really think you’ll like. We’ll see ya next time.
References:
- Dogs of Chernobyl
- Chernobyl dog sticker series
- Ionizing radiation and health effects
- Chernobyl: the true scale of the accident
- Iodine-131
- The dogs of Chernobyl: Demographic insights into populations inhabiting the nuclear exclusion zone
- The Remarkable Comeback of Przewalski’s Horse
- Chernobyl Accident 1986
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