Are Zombies Real?
The short answer
For an ant, a cockroach and a cricket, yes. A fungus, a wasp and a worm each take over a living body and steer it where they need it, and scientists have caught all three in the act. For people, no. No zombie ant fungus is known to infect us, and most fungi can't grow at 37 °C, our body heat.
The film stages the three as acts in a shadow puppet show, then adds a fourth: Toxoplasma, a parasite that works from the brain. About 1 in 4 people carry it. Nobody has shown it steers a human.
How the fungus works an ant
In September 2007, biologist David Hughes and his team followed carpenter ants in a forest in southern Thailand. These ants live high in the trees. Infected ones came down, wandered and shook so hard they fell. Then, around noon, each one bit the underside of a leaf vein about 25 cm above the soil.
The fungus wastes the jaw muscles, so the bite locks shut. The ant can live up to six more hours, and her body stays on the leaf after death. The dead pile up in patches the team called graveyards. A stalk starts to show about four days after death, and the spore bodies take at least 20 days to mature.
In 2017, a Penn State team cut infected ants into very thin slices, imaged every slice and trained a computer to tell fungus from ant. Fungal cells were found throughout the body. They invaded the muscle fibers and joined into networks around them. None were inside the brain. A 2014 study found the fungus releases different chemicals next to ant brains, so it may still act on the brain from outside.
The fungus has enemies too. In Brazilian graveyards, 55.4% of 432 dead ants had other fungi growing on the zombie fungus. Only about 6.5%, roughly 1 in 15, were producing spores. Another 25.5% were simply still immature.
The roach and the cricket
The jewel wasp stings twice. The first sting goes into the chest and stops the front legs for 3 to 5 minutes. The second goes through the soft underside of the neck into the brain, guided by sense organs on the stinger. In 2003, Frederic Libersat's lab gave wasps radioactive amino acids so their venom carried a label, then found that label inside the roach's brain.
The stung roach grooms for about 30 minutes. Then it stops. It is not paralyzed, but it no longer starts walking on its own. In 2008 tests, stung roaches on their backs kicked like healthy ones, and in water they started to swim but quit fast. The wasp leads the roach by an antenna to her burrow, lays one egg on its leg and seals the door. Her larva eats the roach alive from the inside and coats its insides with spit that kills germs. A new wasp walks out about six weeks after the egg is laid.
Roaches can fight back. Kenneth Catania filmed attacks at 1,000 frames per second. Of 27 adults that defended themselves, 17 (63%) were not stung within 3 minutes. Of 28 that did not defend, 24 were stung.
The hairworm grows inside land insects but needs water to mate. Over two years, Frédéric Thomas's team watched an outdoor pool in southern France at night. They saw insects of nine species jump in, and hairworms came out of them. The insects did not seem to sense water from far away. They wandered until they were close, then jumped. In one species the worm is 3 to 4 times longer than its host. In a mountain stream in Japan, infected crickets and grasshoppers were 20 times more likely to enter the water. They supplied 60% of a rare trout population's yearly energy.
Could it happen to us?
Toxoplasma can only mate in a cat's gut, so it waits inside prey such as rats. In a 2000 Oxford study, infected rats lost their fear of cat urine, and some were drawn to it. A 2007 Stanford study found the change is narrow: learned fear, anxiety and the sense of smell all tested normal. In Yellowstone, 26 years of data, with blood tests from 229 wolves, showed infected wolves had 46 times the odds of becoming pack leaders. The authors note the confidence interval just reached zero. It is a link, not proof.
Over 40 million people in the United States carry the parasite, and a 2023 review found it in about 25% of the healthy people studied, about 1 in 4. Most never notice. Scientists still argue about small statistical links in people, and nobody has shown it steers a human.
Fungi have a harder time with us. In 2009, two scientists went through records of 4,802 fungal strains from 144 genera. Most cannot grow at mammal body heat. Each extra degree between 30 and 40 °C ruled out about 6% more, so a fever may help. No zombie ant fungus is known to infect people, and each kind is tuned to its own ant.
The yeast Candida auris was first described in 2009, in Japan, then turned up on three continents at about the same time. One hypothesis is that it adapted to warmer weather until it could survive 37 °C. It is no zombie. It mostly infects people who are already very sick in hospital.
Key numbers
| What | Number | Source |
|---|---|---|
| Height of the zombie ant's death bite | about 25 cm above the soil | Hughes 2011 |
| How long a zombie ant can live after biting | up to 6 hours | Hughes 2011 |
| Age of the fossil leaf with death bite scars, Germany | 48 million years | Smithsonian Insider, 2010 |
| Zombie fungus bodies in Brazil producing spores (of 432 dead ants) | about 6.5% (about 1 in 15); 55.4% overgrown by other fungi | Andersen 2012 |
| Adult roaches that kicked back and were not stung within 3 minutes | 17 of 27 (63%) | Catania 2018 |
| Hairworm length compared with its host (one species) | 3 to 4 times longer | Biron 2005 |
| Insect species seen jumping into the French pool | 9 | Thomas 2002 |
| Share of a rare Japanese trout population's yearly energy from infected insects | 60% | Sato 2011 |
| Odds that an infected Yellowstone wolf becomes a pack leader | 46 times those of an uninfected wolf, from 26 years of data | Meyer 2022 |
| People in the United States carrying Toxoplasma | over 40 million | CDC, About Toxoplasmosis |
| Healthy people carrying Toxoplasma in the studies reviewed | about 25% (about 1 in 4) | Health Science Reports review, 2023 |
| Fungal strains checked for heat tolerance | 4,802; most cannot grow at 37 °C, and each extra °C from 30 to 40 °C rules out about 6% more | Robert and Casadevall 2009 |
What the film simplifies
- The zombie ant fungus is drawn as the Impresario, a showman who runs the whole puppet show. The strings are cartoon: the real fungus works through the ant's muscles, and how it steers her is still being studied.
- The real scientists in the film are drawn as cartoons, not likenesses. Their spoken lines are their own published words.
- The film says each zombie ant fungus is tuned to one kind of ant. In lab tests one species killed every ant species tried, but it only changed the behavior of the ants it infects in nature.
- "46 times the odds" means odds, not 46 times as likely, and the result is borderline: its confidence interval just reached zero. It comes from one study.
- The 37 degrees in the film is Celsius, normal human body heat. The 6% per degree comes from records of strains in a fungus collection, measured between 30 and 40 °C, not from tests on people with a fever.
- "The hairworm" is really several species. The 3 to 4 times length is for one of them, and only some worms escaped the frogs and fish that ate their crickets.
At a glance
Runtime 11 minutes · Topics: Parasites, Fungi, Insects, Animal behavior · Captions on YouTube · Full script below
Test yourself
The zombie ant fungus spreads through the ant's whole body. Where does it not go, and what might it still do there?
Answer
It is not found inside the brain. It may still affect the brain with chemicals released from outside, and scientists are still checking.
A cockroach stung by the jewel wasp is not paralyzed. What evidence shows that, and what does the sting take away?
Answer
On its back it kicks as hard as a healthy roach, and in water it starts to swim. What it loses is the drive to start walking on its own, so the wasp can lead it by an antenna.
Why is the zombie ant fungus not a known danger to people?
Answer
Most fungi cannot grow at our 37 °C body heat, each zombie ant fungus is tuned to its own ants, and none is known to infect people.
The script
Read the script
Host: Are zombies real?
Host: For an ant... yes.
The Impresario: Good evening. Welcome to the oldest show on Earth.
The Impresario: Real puppet masters. Real puppets. And every act... a true story.
Rod: And I sweep up after every act.
Rod: Survived the dinosaurs, kid. Nobody pulls MY strings.
The Impresario: We'll see.
Host: And by the end of the show, he's coming for the biggest puppet in the house.
The Impresario: You.
Rod: Them? They're huge. And they run hot.
The Impresario: I adore a challenge.
The Impresario: Act one. My signature piece.
Host: Thailand. September, 2007.
Host: A biologist named David Hughes and his team are following ants.
Host: These carpenter ants live high in the trees. The infected ones come down.
Host: They wander with nowhere to go. They shake so hard they fall.
The Impresario: Rehearsal.
Host: And then they all do the same thing. Same time of day.
Host: Then, around noon...
Host: ...they bite the underside of a leaf vein.
The Impresario: Noon. I'm a professional.
Host: About 25 centimeters off the ground.
Host: The dead pile up in patches. The team called them graveyards.
The Impresario: I call it a full house.
Rod: Cheerful.
Host: The fungus wastes the jaw muscles, so the jaw locks shut. She can live up to six more hours, and she can't let go.
The Impresario: Holding the pose. It's called discipline.
Rod: And after that?
The Impresario: She hangs around.
Host: Days later, a stalk sprouts from her head. Within weeks, it rains spores on the forest floor.
The Impresario: My encore.
Rod: Every. Single. Act.
Host: In 2017, scientists sliced zombie ants into thin layers and photographed every slice under a microscope.
Host: Then they taught a computer to tell fungus from ant.
Host: The fungus was everywhere. Wrapped around the muscles. Wired together into one big network.
The Impresario: Muscle by muscle. Hand stitched.
Host: Everywhere except the brain.
The Impresario: I never touch the brain.
Rod: Why not?
The Impresario: Darling. I don't need it.
Host: The fungus seems to work the body, not the brain. Hughes compared it to a puppeteer working a marionette.
David Hughes: A fungus in ants' clothing.
Host: Careful, though. It doesn't enter the brain, but it might still send it chemical notes from outside. Scientists are checking.
The Impresario: Allegedly.
The Impresario: Opening night.
Host: A fossil leaf from Germany, 48 million years old, with the same death bite scars zombie ants leave today. Hughes called it the oldest evidence of a parasite steering its host.
The Impresario: 48 million years in show business.
Rod: Rookie.
Host: In 2006, the BBC's Planet Earth showed a fungus killing an ant. A game designer named Neil Druckmann watched it, and found a fresh way to end humanity.
Host: It gave The Last of Us its monster.
Host: He described a fungus that "burrows its way into insects' minds."
The Impresario: MINDS? I never touch the brain! And I never saw a cent.
Rod: So. People next?
The Impresario: Later.
Host: In Brazil, scientists found the zombie fungus gets parasites of its own. Other fungi grow on its stalk and shut it down.
Host: Only about 1 in 15 was spreading spores.
Rod: And they call ME a pest.
The Impresario: We don't talk about them.
Rod: Whole theatre full of puppets.
Rod: Nobody pulls MY strings.
The Impresario: Act two. A lady surgeon.
Rod: A wasp? I've stepped on bigger.
The Impresario: Oh, she's good. Watch her hands.
Host: The jewel wasp. She needs a living cockroach for her baby.
Host: Sting one goes into the chest and knocks out the front legs, so it can't stop sting two.
Host: Sting two goes up through the throat, into the brain. Her stinger can feel its way there.
The Impresario: The BRAIN? Through the THROAT? Barbaric.
The Impresario: ...Lovely technique, though.
Host: In 2003, Frederic Libersat's lab in Israel made the wasps radioactive, so their venom would show up on film. It lit up inside the brain. The first proof.
Rod: They made the wasp RADIOACTIVE?
Host: Only a little.
Rod: Oh good. Much better.
Host: The stung roach grooms itself for about half an hour.
Rod: Looking sharp, kid.
Host: Then it just stops. It isn't paralyzed. It can walk. It just won't decide to.
Rod: I get that every Monday.
Host: In 2008, Ram Gal and Libersat tested it. On its back, it kicked like a healthy roach. In water, it gave up fast.
Host: So she takes it by an antenna and walks it to her burrow. Like a dog on a leash.
The Impresario: Good boy.
Rod: That's somebody's cousin.
Rod: Nope. These stay with me.
Host: She lays one egg on its leg, walls up the door and leaves.
Host: The larva hatches, chews its way in and eats the roach from the inside. While it's still alive.
Host: And it's tidy about it. In 2013, a German team cut tiny windows into roaches and watched the larva coat the inside with spit that kills germs, so its food won't spoil.
The Impresario: A monster with manners.
Host: Weeks later, a brand new wasp walks out.
Rod: No. No no no. Nobody pulls MY...
Rod: ...STRINGS!
Host: That's real. In 2018, Kenneth Catania filmed wasp attacks in slow motion.
Host: Grown roaches that stood tall and kicked her in the head? 63% held her off.
Rod: Survived the dinosaurs. Survived HER.
The Impresario: Bravo. I hate it.
Host: Without a fight, most got stung.
The Impresario: Act three. A water show.
Host: An outdoor swimming pool in the south of France.
Host: Over two years, scientist Frédéric Thomas and his team watched it at night.
Rod: A grown man. Watching a pool. At midnight.
The Impresario: For science.
Host: Insects kept jumping in. Nine different kinds.
Rod: Can't they read? No diving.
Host: The crickets don't seem to sense water from far away. They wander until they're close. Then they jump.
The Impresario: Who's running this act?
Host: The hairworm.
Host: Three to four times longer than the cricket. All coiled up inside.
Rod: How was that IN there?
The Impresario: Packing. It's an art.
Host: The worm swims off to mate. It needed water all along. The cricket was just the ride.
Host: How does it steer? Scientists found the worm makes proteins that look like insect ones. It may be speaking cricket.
The Impresario: A forger. Respect.
Host: In 2006, the same team fed infected crickets to frogs and fish.
Host: Some worms wriggled out. Through the mouth, the gills, even the nose.
Rod: The NOSE?
The Impresario: An escape artist.
Host: And they went on to have just as many babies.
Host: In 2021, scientists in Kobe, Japan found that infected praying mantises go for light that glints the way water does.
Host: A 2024 study found asphalt glints a lot like water. Infected mantises favored it over cement.
Rod: Wrong pool, buddy.
Host: And in a mountain stream in Japan, infected crickets land in the water so often that they make up 60% of the energy a rare trout gets all year.
The Impresario: Zombies, feeding a whole river.
Rod: So they're lunch.
The Impresario: Catering, Rod.
Toxo: Hello.
The Impresario: Act four. Our smallest performer.
Rod: That's the act? It's a dot.
Toxo: Small... is how you get in.
Host: A Prague biologist named Jaroslav Flegr used to cross busy streets like the cars weren't there. He told The Atlantic...
Jaroslav Flegr: If cars honked at me, I didn't jump out of the way.
Host: He wondered what was wrong with him. Hold that thought.
Host: Toxoplasma. A tiny parasite with one goal.
Toxo: I need a cat.
Host: It can only mate inside a cat's gut.
Host: So it rides in a rat, and waits for a cat to eat the rat. Problem: rats run from cats.
Host: Oxford, 2000. Scientists built a pen for rats and scented one corner with cat pee.
Host: Healthy rats stayed away. Infected rats lost their fear. Some went looking for it.
Rod: That's not a zombie. That's a dinner reservation.
Host: In 2007, a Stanford team found it's precise. The rats lose their fear of cat smell. Other fears tested fine.
Toxo: Just the one.
The Impresario: And where do you work from, little one?
Toxo: The brain.
The Impresario: The BRAIN? There are RULES!
Toxo: Strings are... so much work.
Host: It hides in quiet cysts, in muscle and in the brain.
Host: In Yellowstone, scientists matched 26 years of wolf blood tests with how each wolf behaved.
Host: Infected wolves had 46 times the odds of leading a pack. That's a link, not proof.
Rod: Big confident wolf. Must be good at it.
Kira Cassidy: Maybe they're poor leaders.
Host: Back to Prague. In 1990, Flegr joined a faculty that studied Toxoplasma. They needed infected people to test a kit. He gave blood.
Host: He had it.
Rod: Well, that explains it!
Host: Maybe. He's spent decades testing it, and scientists still argue.
Host: Because it's in people too. Over 40 million Americans. About 1 in 4 people on Earth.
Rod: One in FOUR?
Host: Most never notice. In people, scientists find small statistical links, and they still argue about them. Nobody has shown it steers a human.
Joanne Webster: In the vast majority of people, there will be no ill effects.
Host: And to the parasite, you're a dead end. Its only way home is a cat, and cats rarely eat you.
Toxo: Wasted trip.
Rod: Lucky us.
The Impresario: And now. The biggest puppet in the house.
The Impresario: For you... I'd even touch the brain.
Rod: You said later.
The Impresario: It IS later.
Host: Could it happen to us? In 2009, two scientists checked 4,802 strains of fungi. Most can't grow at our body heat. 37 degrees.
The Impresario: Hot. Hot. HOT.
Host: And every degree of fever shuts out about 6% more.
Rod: A fever. Best bouncer in the business.
Host: No zombie ant fungus is known to infect people. Each kind is tuned to one kind of ant.
The Impresario: Ants it is.
Host: A yeast called Candida auris was first named in 2009, then turned up on three continents at about the same time.
Host: Some scientists think it got used to warmer weather until it could survive our 37 degrees. That's a hypothesis. And it's no zombie. It mostly infects people already sick in hospital.
The Impresario: Learning to take the heat. How interesting.
Rod: Don't.
Host: So, are zombies real? For an ant, a cockroach and a cricket... yes.
Rod: You, though? Nobody pulls YOUR strings.
Rod: ...Is he...?
Host: Probably just a cat person.
Sources
- Infected carpenter ants in southern Thailand (September 2007) come down from the canopy, wander and convulse, bite the underside of a leaf vein around noon about 25 cm up, die in patches called graveyards, and stay locked on after the jaw muscles waste; ants may live up to six hours after biting.Hughes 2011
- Fungal cells are found throughout the ant's body, invade the muscle fibers and join into networks around the muscles, but are not found in the brain.Fredericksen 2017
- Thin slices imaged one by one and a computer trained to tell fungus from ant; Hughes: a fungus in ants' clothing, like a puppeteer working a marionette; the brain may be chemically altered.Penn State, 2017
- The fungus secretes different chemicals next to ant brains, and its behavior control is species specific.de Bekker 2014
- A 48 million year old fossil leaf from Germany shows the same death bite scars; Hughes calls it the oldest evidence of a parasite steering its host.Smithsonian Insider, 2010
- The BBC's Planet Earth (2006) inspired the monster of The Last of Us; Druckmann describes a fungus that burrows its way into insects' minds.NPR, 2013
- In Brazil, other fungi grow on the zombie fungus: of 432 dead ants, 55.4% were hyperparasitized, 25.5% immature, and only about 6.5% producing spores; the stalk shows about 4 days after death.Andersen 2012
- Wasps given radioactive amino acids deliver labelled venom into the cockroach brain, the first direct evidence of venom injected into a prey's brain.Haspel 2003
- The first sting into the thorax stops the front legs for 3 to 5 minutes; the second goes through the neck into the brain, guided by sense organs on the stinger.Gal 2014
- Stung roaches are not paralyzed but do not start walking on their own; the wasp walks them to her nest by an antenna like a dog on a leash.Gal and Libersat 2008
- Stung roaches turned on their backs kick as hard as normal roaches, and in water they start to swim but give up quickly.National Geographic, 2008
- Through small windows in the cuticle, the larva was seen coating the roach's insides with an antimicrobial secretion; the adult wasp emerges about 6 weeks after the egg is laid.Herzner 2013
- Filmed at 1,000 frames per second: 17 of 27 adult roaches that defended themselves (63%) were not stung within 3 minutes; 24 of 28 that did not defend were stung.Catania 2018
- Over two years at an outdoor pool in southern France, insects of nine species jumped into the water and hairworms emerged; the insects show no sign of sensing water from far away.Thomas 2002
- The hairworm makes proteins that mimic insect proteins; the worm is 3 to 4 times longer than its host.Biron 2005
- Hairworms can escape from a fish or frog that ate their insect host.Ponton 2006
- Infected praying mantises are drawn to horizontally polarized light, the kind water reflects.Kobe University, 2021
- Asphalt reflects light much like water, and infected mantises walked on asphalt roads more often than on cement roads.Sawada 2024
- In a Japanese mountain stream, infected crickets and grasshoppers were 20 times more likely to enter the water and supplied 60% of an endangered trout population's annual energy intake.Sato 2011
- Flegr crossed streets in dense traffic and did not jump when cars honked; in 1990 he gave blood to test a kit and found he had the parasite; Webster: in the vast majority of people there will be no ill effects.The Atlantic, 2012
- Over 40 million people in the United States carry Toxoplasma; cats are its home host; most healthy people have no symptoms.CDC, About Toxoplasmosis
- Infected rats lose their aversion to cat odor, sometimes turning it into attraction.Berdoy 2000
- Infection removes the fear of cat odor while learned fear, anxiety and smell test normal.Vyas 2007
- 26 years of Yellowstone wolf data, 229 wolves tested: infected wolves had 46 times the odds of becoming pack leaders; the confidence interval just reached zero.Meyer 2022
- Kira Cassidy on infected pack leaders: maybe they're poor leaders.KUNC, 2022
- About 25% of healthy controls carry Toxoplasma, about 1 in 4.Health Science Reports review, 2023
- Of 4,802 fungal strains from 144 genera, most cannot grow at mammal temperatures; each 1 °C rise from 30 to 40 °C excludes another 6%.Robert and Casadevall 2009
- The zombie ant fungus presents no threat to people; the human body is too warm for it.University of Calgary, 2023
- Candida auris, first described in 2009 in Japan, emerged on three continents at about the same time, mostly in very sick hospital patients.Lockhart 2017
- Candida auris may be the first new fungal disease to emerge from a warming climate, a hypothesis with caveats.Casadevall 2019