If you are entangled by an Amazonian green anaconda, can a sharp dagger help you escape?

If you’re in the Amazon rainforest and a 7-meter-long, over 200-kilogram green anaconda has you wrapped up, and you just happen to have a sharp dagger in your hand—can you actually survive? This isn’t a movie plot. In 2014, American environmentalist Paul Rosolie did exactly such a “self-destructive experiment.”

He covered his body in pig blood, wore a custom carbon-fiber protective suit worth a million dollars, and lay in a muddy patch, waiting for a 7.6-meter-long, 230-kilogram green anaconda to coil around him. The protective suit could withstand 300 pounds per square inch of pressure, and in theory it could hold up to a constrictor’s squeezing.

What he didn’t expect was that the instant the anaconda tightened around him, Paul heard a snap as his ribs fractured. Fifteen seconds later, his heart rate surged to 180, and he sent out a distress signal before suffocating. Staff risked their lives to pull him out; the experiment ended—Paul had broken three ribs.

From the moment of constriction to the moment of rescue, the whole process took under a minute. If it weren’t for the fast actions of the experiment personnel nearby, it wouldn’t have been just broken ribs—his life would have ended there. So, if you have a sharp dagger in hand, in this kind of situation, could you complete a self-rescue? Let’s talk about this interesting question.

The green anaconda, whose scientific name is Eunectes murinus, is the heaviest snake that currently exists in the world. Its size statistics—at least online—are “blown way out of proportion,” but in reality, all those “10 meters, 40 meters” rumors you see online are false.

In 1978, herpetologist Williams LaMarr recorded a female green anaconda in Colombia measuring 7.5 meters long, weighing about 136–181 kilograms. This is already the largest individual with reliable documentation. Previously, there was even a reward of $50k for capturing a green anaconda longer than 9.1 meters, but to this day, no one has claimed the prize.

A new 2024 study confirms that the northern green anaconda is one of the largest snake species currently living, with a documented maximum individual measuring 7.5 meters long and weighing about 180 kilograms. Of course, there’s still debate over this weight figure, but one thing is certain: adult green anacondas are at least 100 kilograms—to humans, they’re basically tiny.

So how strong is a green anaconda’s combat power, exactly?

First, it’s powerful. A green anaconda’s constriction force reaches 130+ pounds per square inch, which is like placing a 10-ton boulder on an object. Once it coils, a person’s ribs can be crushed within seconds, puncturing the heart and lungs and causing instant suffocation.

Second, once it bites, it doesn’t let go. The anaconda’s mouth is full of inward-curving teeth. When it bites prey, it hooks on like a fishhook— the more you struggle, the deeper it bites. Once it has you in its jaws, getting free is basically impossible.

Third, in water it’s “in its element.” Most of the time, green anacondas stay in water. Their swimming speed can reach 30 kilometers per hour, while humans can’t even match a small fraction of that in water.

Fourth, it’s a “cold-blooded killer.” It will sense your heartbeat first. During constriction, it keeps tightening until your heartbeat stops, and only then does it begin to swallow. You want to wait for it to loosen? You’d have to wait until it confirms you’re already dead.

Let’s break it into two scenarios.

Scenario 1: You’re already being constricted.

This is Paul’s experience. The anaconda’s coiling speed is extremely fast—from bite to full tightness, it may take only a few seconds. Once your body is wrapped, your arms get pinned to the sides. You can’t even breathe properly, let alone swing a blade.

Even if you somehow manage to pull your arm free, where are you going to stab? Green anacondas are covered in scales, and their Mohs hardness is comparable to copper products. Under the scales is 10 centimeters of fat and muscle. If you stab down, you may not even get through the muscle layer, and you might actually enrage it, causing it to tighten even more.

There’s been a case in Pennsylvania like this: in 2022, a man named Senman was wrapped around the neck by his own 5.5-meter red-tailed boa. After police arrived, they shot and blew up the snake’s head to save him, but he still died four days later from hypoxic brain damage. And this was only a neck constriction—not full-body coiling.

So, after being constricted, a knife basically has no chance. Paul broke three ribs even while wearing a protective suit. How long could you last in a T-shirt?

Scenario 2: You haven’t been constricted yet—you’ve only been bitten.

This is the only possible chance for self-rescue.

When boas and pythons attack people, they generally bite first and then start to coil. While it has you bitten, it hasn’t begun constricting yet, so your arms can still move. At this time, you’re very close to the snake’s head, and not that far from its heart—the snake’s “seven-inch,” meaning the heart area, is roughly one-quarter to one-third of its body length from the head.

What you need to do then is: use all the strength you have and stab toward the snake’s heart area, or stab its eyes or its cloaca (the large scale patch under the tail).

Snakes have two vital points: the eyes and the cloaca. These areas have no scale protection and are extremely vulnerable. Jab hard at these spots, and the snake will loosen its grip due to intense pain. In 2019, there was a report of an American man who was constricted by a python and managed to escape by biting the snake’s tail (actually, he hit its cloaca).

But completing a self-rescue depends on two prerequisites:

First, you must finish the attack before it begins to coil you. Once it coils, you lose your chance.

Second, you have to get the position right. A green anaconda’s heart is hidden under thick muscle. If your blade isn’t long enough or sharp enough, you may not be able to reach the vital spot at all. So, if you can accurately stab the eyes or find the cloaca and strike, your chances of self-rescue become very high.

So, if you’re holding a dagger and a green anaconda coils around you, it’s most likely a matter of survival against overwhelming odds—you’re almost certainly not getting out alive.

To be honest, you probably won’t encounter this. Green anacondas mainly live in the Amazon River basin in South America, not in China. And they’re generally afraid of people and usually won’t attack proactively. But if you truly do run into one, it’s not the end of the world. You just need four moves:

First, maintain distance. Don’t approach. Don’t provoke. Give it a way to escape, and it will choose to run. If you’re facing off, back away slowly while keeping it in front of you, and once you’re outside its warning zone or territory, you’re safe.

Second, if it has already bitten you, never yank it hard. Its teeth curve inward. The more you pull, the deeper it bites. What you should do is, while searching for its vital points, also shout for help.

Third, never play dead. Snakes don’t mind eating dead prey, and feigning death actually makes it easier for them to take a bite.

Fourth, if it has already started to coil you, your only chance is to get your hand between your neck and the snake’s body before it tightens fully, giving yourself a little breathing room, while urgently calling for help. If one person is constricted, they basically can’t self-rescue—they need someone else.

Even though a dagger is a powerful edged weapon, in the face of a green anaconda’s absolute strength, it may not even count as self-defense.

Paul spent $100k and wore the top-tier protective suit, and he only lasted for a dozen or so seconds. If you’re wearing a T-shirt and jeans and holding a kitchen fruit knife, don’t overthink it. That said, nothing is absolute. If you know the snake’s weak spots and use all your strength to hit it before you’re fully wrapped, you will most likely be able to self-rescue. And in the wild, no matter what snake you encounter, keeping your distance works better than any weapon you might carry.