How Does an Anaconda Snake Kill Its Prey? Science of Constrictors Explained

In recent years, it has been discovered that boa constrictors, anacondas, and other nonvenomous constrictor snakes kill their prey by inducing cardiac arrest rather than suffocation. This means that the constriction process is quicker and more efficient than previously thought. When these snakes wrap their coils around their prey, they apply pressure that essentially stops the blood flow and oxygen supply, causing the prey’s heart to stop beating within seconds.

When it comes to constricting snakes like anacondas and pythons, the common belief has been that their victims die due to asphyxiation caused by the pressure exerted by the snake’s coils. However, recent scientific research has challenged this long-held assumption, suggesting that the cause of death may be something entirely different.

In this blog post, we will delve into the fascinating world of constrictors and explore the latest theories regarding their lethal grip. Join us as we unravel the truth behind these deadly encounters.

The Traditional Theory of Asphyxiation

For many years, scientists and experts believed that constricting snakes strangle their victims to death by preventing them from breathing. The idea was that the pressure exerted by the snake’s coils around the chest would inhibit the expansion of the lungs, leading to asphyxiation. This theory seemed logical, given the immense force constrictors can generate.

However, recent observations and studies have cast doubt on this traditional theory, prompting researchers to reevaluate the cause of death in constrictor attacks.

A Lack of Struggle

One of the significant factors that have challenged the traditional theory is the absence of evidence of struggle in incidents involving constrictor attacks. Victims show no signs of attempting to free themselves from the tightening grip of the snake. This raises questions about whether asphyxiation is truly the primary cause of death in these cases.

The Cardiac Arrest Hypothesis

A new theory has emerged to explain the absence of struggle observed in constrictor attacks. According to this hypothesis, the pressure exerted by constrictors on their victims’ chests is so intense that it prevents the heart from expanding during diastole.

As a result, immediate cardiac arrest occurs, leading to rapid death. In essence, it is as if the snake squeezes the life out of its victim by compressing the heart and preventing blood from circulating effectively.

Anaconda Prey and Hunting Technique

As a constrictor snake, the anaconda uses its powerful muscles to subdue and kill its prey. Anacondas rely on their rib muscles to expand and contract their ribs, enabling them to wrap around their prey and squeeze them to death.

In the wild, anacondas are opportunistic hunters, preying on a variety of animals that inhabit their surrounding environment. Their diet can consist of small turtles, diving birds, fish, and even mammals such as capybaras, deer, and caiman. Anacondas have been known to occasionally target larger prey, but smaller animals make up the majority of their diet.

Anacondas’ hunting techniques are efficient and stealthy. They often use their natural camouflage to blend in with their surroundings, remaining hidden from their prey until the opportune moment arrives. By staying in or near water, anacondas take advantage of their excellent swimming abilities and utilize the water’s buoyancy to support their massive bodies.

Once their prey is within striking distance, anacondas move with impressive speed and precision. They lunge forward, sinking their sharp, backward-pointing teeth into the prey to secure a firm grip. Afterward, they quickly wrap their powerful, muscular bodies around the victim, constricting it until it dies.

It is worth noting that green anacondas in the wild are not particularly aggressive and will generally avoid unnecessary confrontation. However, when threatened or harassed, they can defend themselves quite effectively, employing their size, strength, and powerful bite.

After successfully killing their prey, anacondas swallow the victim whole. Digesting a meal can take several days, depending on the size of the prey. During this time, the anaconda may remain inactive, allowing its body to focus on breaking down and absorbing the nutrients from its meal. This allows the snake to go for extended periods without needing to hunt again.

Documented Cases of Humans being Killed by Anacondas

There have been several documented cases of human deaths caused by anacondas.

One of the most well-known cases occurred in 2014 in the Amazon rainforest of Brazil. A 25-year-old man named Paulo Roberto da Silva was attacked and killed by an anaconda while he was fishing in a remote part of the river. According to reports, the snake was over 23 feet long and weighed more than 300 pounds. It wrapped itself around da Silva and suffocated him before dragging him underwater.

Another case occurred in 2017 in Indonesia, where a 25-year-old man named Akbar was attacked and killed by an anaconda while he was harvesting palm oil. According to reports, the snake was over 23 feet long and weighed more than 500 pounds. It is believed that the snake attacked Akbar after he accidentally disturbed it while working in the plantation.

These cases serve as a reminder of the danger posed by these large and powerful snakes, and the importance of respecting their habitats and behaviors.

In many areas, anacondas may be killed in retaliation for livestock consumption and perceived risk to humans. Their fat is widely used for its supposed curative properties. Anaconda leather has commercial value, which also contributes to human-animal conflicts.

Overview of Constriction

Latest Science shows Constrictors kill by inducing cardiac arrest

Constriction begins when the snake strikes at its prey and holds on, pulling the prey into its coils. Once the prey is secured within the coils, the snake applies pressure by tightening its muscles. This pressure causes circulatory distress in the prey, leading to a rapid drop in blood pressure and cardiac arrest.

Snakes are equipped with specialized muscles that allow them to apply and maintain a constant force on their prey without tiring. Furthermore, constrictor snakes can sense the heartbeat of their prey and will continue to apply pressure until they no longer feel the prey’s pulse.


The strength of a constrictor snake is truly remarkable. For example, anacondas, which are among the largest and most powerful constrictors in the world, can exert a force of up to 90 pounds per square inch (psi) when constricting their prey.

To put that into perspective, that’s about the same amount of pressure as a strong water jet hitting your body at full pressure. The strength of the constriction is also dependent on the size and species of the snake, as well as the condition and size of the prey.

Here are some estimates of the constrictive forces exerted by different snake species:

  • Green Anaconda (Eunectes murinus): 90 psi
  • Burmese Python (Python bivittatus): 80 psi
  • Boa Constrictor (Boa constrictor): 60 psi


The duration of constriction varies depending on the species of snake, the size and type of prey, and the snake’s overall strength. In general, constriction can last anywhere from a few seconds to several minutes.

It is important to note that constriction is an energy-intensive process for the snake. Consequently, snakes will try to balance the energy expended on constriction with the energy they will gain from consuming their prey. This means that, in some cases, the duration of constriction may be shortened if the snake determines that it would require too much energy to continue the process.

In summary, constriction is a highly effective method employed by a variety of snake species to subdue and kill their prey. The latest research indicates that snakes induce cardiac arrest in their prey through this mechanism, as opposed to causing suffocation as was previously believed. The strength and duration of constriction can vary based on factors such as snake species, prey size, and the snake’s overall strength and energy levels.

Constrictor Snakes besides Anaconda

In addition to anacondas, there are other types of constrictor snakes, such as pythons and boas, that share similar methods of subduing and killing their prey. These powerful and fascinating creatures use their muscular bodies to coil tightly around their victims, applying pressure and cutting off blood flow to ultimately cause their demise.


Pythons, like anacondas, are non-venomous snakes that rely on constriction to take down their prey. With remarkable patience and stealth, they lie in wait for the opportune moment to strike, grabbing their victim with their sharp teeth before coiling around them.

You may find pythons in various habitats, such as grasslands, jungles, and swamps, spread across Africa, Asia, and Australia. There are numerous species of pythons, with some being quite small, while others, like the reticulated python, can grow up to a staggering length of 20-30 feet. These incredible reptiles are known for their ability to swallow prey much larger than their own body size, thanks to their expandable jaws.

While pythons are efficient predators, they do not pose a significant threat to humans unless provoked or under threat. Moreover, larger species of pythons, such as the Burmese python, are known to have an impact on native ecosystems when introduced as invasive species.


Boa constrictors are another group of non-venomous constrictor snakes that share similar hunting strategies with pythons and anacondas. They are typically found in the Americas, from North to South, inhabiting diverse environments like forests, deserts, and grasslands. Boa constrictors display a remarkable range in size, with some species like the Sand Boa reaching lengths of only 2 to 3 feet, while others, such as the Emerald Tree Boa, may grow up to 8 feet long.

Boas are known for their exceptional camouflage capabilities and their use of ambush tactics to catch their prey. They typically hold onto branches with their prehensile tails and patiently wait for an unsuspecting meal to come within reach. Once the prey is within striking distance, the boa quickly grasps it with its teeth and wraps its muscular coils around the victim, compressing until the prey succumbs to the pressure.

An interesting fact about boas is that they give birth to live young, instead of laying eggs like pythons and many other snake species. Their unique reproductive capabilities, combined with their strong predatory skills, make them a captivating group of constrictor snakes.

Effects on Prey

Immediate Impact: Suffocation or Cardiac Arrest?

As you observe an anaconda or another constrictor snake attacking its prey, you might wonder whether the victim dies from suffocation or cardiac arrest. It turns out that the common belief that these snakes suffocate their prey is incorrect. Recent research has shown that constrictor snakes kill primarily by cutting off blood circulation to their prey’s vital organs, rather than depriving them of air (The Atlantic, March 24, 2022).

Yellow anaconda coiled on forest floor in Peru
Yellow anaconda coiled on forest floor in Peru

When a snake such as a boa constrictor or an anaconda attacks its prey, it uses its powerful muscular body to throw two or three loops around the victim’s torso, similar to a straitjacket (The Wire Science). With each breath the prey takes, the snake tightens its coils further, preventing the prey from inhaling fully. This decreases the blood flow to vital organs, resulting in blood vessels being compressed, leading to circulatory failure and eventually cardiac arrest (National Geographic, July 22, 2015).

Consequences when a constrictor attacks

While it is clear that constrictor snakes can effectively kill their prey, there are additional consequences for the prey:

  • Inability to escape or fight back: Anacondas, constrictors, and other nonvenomous snakes rely on their ability to immobilize their prey by constriction, rendering the victim unable to move or resist capture. Once entwined, the prey has little to no chance of escaping or fighting back against their attacker.

  • Energy expenditure and exhaustion: The struggle between constrictor snakes and their prey can be a long, drawn-out process, as the snakes work to tighten their grip and the prey attempts to free itself. During this intense struggle, prey often depletes their energy reserves, further reducing their chances of survival.

Constriction Efficiency and Success Rate

The constriction process starts when the snake strikes its prey and immediately wraps its body around it. Utilizing their strong muscles and the tactile receptors on their skin, constrictors can sense their target’s heartbeat and adjust the force of their squeeze accordingly. It is important to note that the snake will not waste energy by squeezing harder than necessary but will instead maintain an optimal pressure to ensure the prey’s timely death.

Several factors contribute to the efficiency of constriction, including:

  • Size and strength: Larger and stronger snakes like anacondas can exert greater force on their prey, making it difficult for the prey to escape and causing their rapid death.
  • Sensory systems: Constrictor snakes have specialized sensory organs that aid in detecting their prey’s movement, heartbeat, and even breathing. This allows them to adjust their constriction force accordingly and maintain a constant pressure on the target.
  • Ambush hunting: Many constrictor snakes are ambush predators that rely on stealth rather than speed. By striking quickly and decisively, they can subdue their prey before they have a chance to react, ensuring a successful kill.

Aside from their ability to effectively immobilize and kill their prey, the constriction method has another advantage: minimal risk of injury. When you compare constrictors to venomous snakes or other predators that rely on claws or teeth, their method carries a lower risk of getting injured during the hunt. By squeezing their prey instead of biting, constrictors can maintain a safe distance from the target’s dangerous defenses.

In terms of success rate, constrictor snakes are generally adept at securing their meals. While precise success rates vary between species, habitat, and the prey type, their powerful constriction ability and highly adapted sensory systems contribute to their overall hunting prowess. However, it is important to remember that variables such as the availability of prey or competition with other predators might also impact their success in hunting.

Latest Research on Constrictor Adaptations

This new understanding of constrictor killing techniques has also provided valuable insight into their physiological adaptations. For instance, boa constrictors have developed a unique ability to inflate only parts of their lungs while constricting their prey, allowing them to maintain respiration even as they apply immense pressure to their victim’s body.

When faced with large and potentially dangerous prey, constrictor snakes must carefully balance the use of force with their own safety. If they apply too much pressure, they risk injury from their struggling prey. Conversely, if they apply too little pressure, the prey may escape or cause harm to the snake.

To calculate the appropriate force, constrictor snakes utilize sensory organs called mechanoreceptors, which are located in their skin, muscles, and other tissues. These mechanoreceptors help them detect changes in pressure and respond accordingly. This enables the snake to continually adjust the force of constriction, ensuring that they use the minimum necessary pressure to subdue their prey efficiently without causing self-harm.

Myths and Misconceptions

In the world of constrictor snakes, such as anacondas and pythons, there are several myths and misconceptions that you might come across. This section will help you to debunk some common misconceptions and to understand these fascinating creatures better.

Myth 1: Constrictor snakes suffocate their prey

The most common myth about constrictor snakes is that they kill their prey by suffocation. However, recent studies have shown that this is not true. Instead of suffocating their prey, these predators actually cut off their victims’ blood supply, causing a rapid drop in blood pressure and leading to unconsciousness and death. This method allows constrictor snakes to subdue their prey more quickly than previously believed.

Myth 2: Anacondas and pythons measure their prey before eating it

Another misconception is that anacondas and pythons measure their prey before deciding to eat it. This idea is based on the false assumption that these snakes have some sort of built-in tape measure to assess whether the prey will fit into their mouths. In reality, constrictor snakes do not have such an ability and do not measure their prey before eating it. Instead, they rely on their flexible jaws and the elasticity of their skin to accommodate various sizes of prey.

Myth 3: Anacondas have a taste for humans

A popular myth in South American folklore is that anacondas, particularly the green anaconda, have a taste for humans and actively hunt for them. However, this is far from the truth. While anacondas are indeed capable of eating a human, such occurrences are extremely rare. These snakes are opportunistic predators and prefer to feed on more easily accessible prey, such as rodents, birds, and other smaller mammals.

Myth 4: Constrictor snakes are slow and sluggish

Contrary to popular belief, constrictor snakes are not slow or sluggish creatures. Although they are not as fast as some other types of snakes, they are more than capable of ambushing their prey with surprising speed when necessary. In fact, the anaconda’s ability to remain almost completely submerged in water allows it to stealthily approach and ambush its prey.

To better understand these amazing creatures, it’s important to dispel these myths and misconceptions about their behavior and hunting methods. Now that you’re aware of the truth behind these misunderstandings, you can appreciate the unique abilities and characteristics that make constrictor snakes such impressive and fascinating predators.

Human Interaction and Safety

Anacondas are infamous for their striking physical presence and powerful hunting techniques. However, it is essential for you to understand their actual behavior and the risks they pose to humans. This way, you can ensure the safety of both humans and these fascinating creatures.

Now, let’s discuss human-anaconda conflicts. While there have been a few instances of anacondas attacking humans, it is relatively rare. In most cases, the snake perceives a human as a threat and reacts defensively. It is essential for you to maintain a safe distance, avoid interfering with the snake, and never corner or provoke it. If an anaconda feels threatened, it may attack in self-defense or attempt to flee.

Stay Aware in Anaconda Country

We don’t tend to think of ourselves as potential prey or menu items, but when you are in anaconda country you need to consider what anacondas are capable of.

When visiting areas inhabited by anacondas, here are a few vital safety tips to keep in mind:

  • Stay informed and aware: Understand the local ecosystem and risks involved. Consult local authorities and experts for guidance.
  • Maintain distance: Avoid provoking or interacting directly with snakes. If you spot an anaconda, observe from a safe distance.
  • Travel in groups: Larger groups of people deter predators more effectively than lone individuals.
  • Avoid feeding wildlife: Offering food to any wild animal can encourage unwanted behavior, making them more likely to approach humans.

Finally, take into account the ecological significance of anacondas and other constrictor snakes. They play an essential role in controlling the populations of their prey, maintaining a balanced ecosystem.

Frequently Asked Questions

How do constrictors immobilize their prey?

Constrictors, like anacondas, immobilize their prey by wrapping their muscular bodies around the prey and applying pressure. As the prey exhales, the snake tightens its grip, preventing the prey from taking in another breath. This process continues until the prey is successfully immobilized or dies from lack of oxygen.

Do Anacondas have venom? Do any constrictors use venom?

Anacondas and other constrictor snakes do not possess venom. They rely solely on their powerful constriction ability to subdue and kill their prey. Venomous snakes typically have hollow, needle-like fangs through which they inject venom into their prey, while constrictors have curved, non-venomous teeth designed for grasping and holding prey.

What mechanism allows constrictors to kill their prey?

Constrictors kill their prey by applying immense pressure around the prey’s body. This pressure can either cut off the blood flow to vital organs, like the heart and lungs, or significantly restrict the prey’s ability to breathe. As a result, the prey ultimately succumbs to organ failure or suffocation.

Are constrictor jaws unhinged to swallow prey whole?

Constrictor snakes have highly flexible jaws that enable them to swallow their prey whole. While their jaws are not completely unhinged, the ligaments and muscles connecting the two halves of the lower jaw can stretch significantly. This allows the snake to consume prey much larger than its head diameter.

How do pythons and boas differ in their hunting techniques?

Both pythons and boas are constrictor snakes, but they demonstrate some differences in hunting techniques. Pythons tend to be more ambush predators, relying on stealth and camouflage to surprise their prey. Boas, on the other hand, actively chase and corner their prey before constricting and killing them.

What is the strongest constriction force recorded in snakes?

The strongest constriction force recorded in snakes was observed in the green anaconda, which can exert a pressure of around 90 pounds per square inch (PSI). To put this into perspective, this is equivalent to having 65 gallons of water sitting on a dime-sized area of your body.

How do constrictors sense when their prey is dead?

Constrictor snakes are sensitive to the heartbeat and movements of their prey. As the prey’s heartbeat weakens or stops, and its movements cease, the snake gradually releases its grip. Once the snake is confident that its prey is no longer alive, it will begin the process of swallowing it whole.

Can constrictor snakes pose a threat to humans?

Although constrictor snakes are not typically aggressive toward humans, they can pose a threat if they feel threatened or cornered. Most constrictors are not large enough to kill an adult human; however, larger species like green anacondas and reticulated pythons have been known to cause injury and, in extremely rare cases, fatalities. It is always best to give these animals the space and respect they deserve to avoid potential conflicts.