Why Are Pigs Aggressive to People, Animals? Safety Solutions

Dealing with 650 lb of angry pig is no joke. It compromises the welfare of other pigs within the herd and endangers anyone involved in handling those animals. 

Our first boar was so aggressive that we slaughtered him as soon as he reached market weight. Before that, he bit several people, including myself. 

In contrast, our current boar is a pushover. A quick scratch behind the ears, and he rolls over like a dog looking for a belly scratch. 

What makes pigs aggressive? Pigs are naturally aggressive. They use violence to establish dominance within their social group or protect a valuable resource. A pig that’s aggressive towards people is potentially dangerous. Such behavior needs to be corrected quickly through socialization, training, and improved nutrition and pen design. 

Pigs are Naturally Aggressive 

Pigs are social animals that use aggression to establish a social hierarchy. A dominance-subordinate relationship underpins the social structure of the herd. 

Pigs become aggressive and engage in violent fights when mixing with unfamiliar animals. This type of aggression is usually short-lived, lasting between 24 to 48 hours. Once the pigs have established their social hierarchy, the fighting soon subsides. Any lack or scarcity of vital resources like space, water, or feed will aggravate the animal’s natural aggression. Situations like these lead to increased competition and fierce conflicts. 

Dominant pigs are more likely to engage in aggressive interactions than submissive pigs. Not only do they engage in more conflicts, but those fights also last longer, increasing the risk of injury.  

Age also influences a pig’s level of aggression. A study on the effects of mixing on the aggressive behavior of commercially housed pigs found that animals aged between 25 and 50-days old were more likely to engage in aggressive behaviors than older pigs of 75 days. 

Boars or male pigs are more aggressive than sows, although they take longer to engage in a conflict. 

In the wild, boars compete with one another over territory and mates. Several factors may exacerbate this natural aggression within a domestic or commercial environment. 

10 Reasons Pigs Become Aggressive

Pigs aren’t usually aggressive, but there are situations that make them more aggressive, leading to dangerous circumstances. Let’s dive into ten reasons pigs become more aggressive. 

#1 Mixing Unfamiliar Pigs Causes Aggression 

Pigs exhibit aggressive behavior when introduced to unfamiliar animals, including other pigs. They use these conflicts to establish a social hierarchy. Once that dominance-subordinate relationship is in place, the aggressive behaviors will diminish before disappearing. 

Other factors are at play if the aggression continues within a stable group. 

#2 Genetics Have an Impact on Pig Aggression

Researchers in Sweden and Denmark compared the behaviors of two distinct pig populations. Their findings showed that both aggression and bullying are moderately heritable. Some pigs are genetically predisposed to conflict, while others are naturally submissive. Studies suggest that the genes NR3C1 and AVPR1B are responsible for this aggressive trait.

Aggression is often an individual trait. Among pigs of the same breed, individual traits of aggression can be passed down. If your pigs are showing aggression and none of the other factors are applicable, you may want to bring in pigs with calmer dispositions. 

#3 Pigs Fight when Resources are Limited

Food or water scarcity causes pigs to fight over those vital resources aggressively. A pig needs dry, warm areas to rest and access to both water and feed. If any of these are in short supply, conflicts will inevitably occur. 

#4 There is a Link Between Poor Air Quality and Aggression  

Higher concentrations of ammonia in the air may increase aggression in pigs. Researchers believe this is associated with the pig’s limited ability to regulate its body temperature. As a result, sudden changes in temperature and air quality cause stress which can, in turn, result in more aggressive behaviors. 

Ideally, pigs should have different temperature zones within their enclosures. Insulation in the sleeping area ensures thermal comfort, while providing sprinklers or wallows in the foraging area will help keep them cool while active.

#5 Limited Space can Increase Fight Frequency and Severity

Pigs are social animals that benefit from positive social interactions. However, the correct stocking density is critical. Overcrowding can increase both the frequency and severity of negative social interactions. Limited space availability also makes it difficult for subordinate pigs to escape their aggressors, increasing the likelihood of harmful, violent interactions and the possibility of injury.

#6 Poor Nutrition Increases Aggression and Tail-biting

Tail-biting is a common type of aggression seen in commercial pig farms. It occurs when the aggressors chew on the tail of a subordinate animal. Once tail biting begins, it can be tough to stop. The smell of blood also attracts pigs and may cause them to continue biting until the victim requires euthanasia. 

Studies show that pigs on a low-protein diet who lack the opportunity to forage are more likely to engage in this destructive behavior. Researchers have also found a link between a low-sodium diet and tail-biting. 

Boredom and disease can also increase such aggressive tendencies.  

#7 Enriching the Environment can Reduce aggression

Pigs that are kept indoors without the ability to forage need alternative forms of stimulation. Without these, they’re more likely to practice their natural chewing behavior on each other. Providing pigs with “manipulable enrichment materials” such as balls, chains, and rubber hoses can help prevent tail-biting and other forms of aggression.

#8 Heavier Animals Fight More Frequently

A pig that weighs 300 lb or more understands that its increased bodyweight gives it an advantage in a conflict. Therefore, heavier animals tend to be more self-confident and aggressive. They are more likely to engage in violent interactions, and because of their weight, those aggressions are likely to be more intense and potentially damaging.  

#9 Gender Influences Levels of Aggression

With a natural tendency to fight over mates and territory, male pigs tend to be more aggressive than females. They may also exhibit more aggressive behavior when breeding. The proximity of a sow that’s ready to breed may exacerbate this aggression. 

#10 Mishandling can Make a Pig Aggressive

Pig owners that treat their animals as part of the family rather than as farm animals may find their pigs become aggressive. Pigs raised indoors without the opportunity to socialize with other swine may become destructive or belligerent. 

Find out more about how to correctly handle a pet pig here. 

The Impact of Aggression on Pig Welfare

Aggression within a herd of pigs can:

  • Cause stress
  • Negatively impact the growth rate
  • Suppress an animals immunity
  • Lead to injury, infection, and potentially death

Pigs that suffer sustained attacks by more than one aggressor will develop sores and lesions. These are usually the result of biting. They may also show signs of lameness and exhaustion. 

According to Dr. Simon Turner, a senior researcher in animal behavior at Scotland’s Rural College, any conflicts between pigs are stressful for both the aggressor and the victim. The injuries are also painful and prone to infection. 

An animal that’s in pain is more likely to become aggressive towards its handlers and other pigs, but that’s not the only reason pigs bite humans.

Most Aggressive Pig Breeds

Of all the domestic pig breeds, the most aggressive pig breed is the Hampshire. While Hampshire sows are generally docile and friendly, boars can be difficult to handle. Historically, Durocs have been considered aggressive, but breeders have managed to breed out much of that aggression. It is now considered one of the calmest pig breeds but it is, nevertheless, a trait to be aware of when selecting the best pig breed for your home or homestead.

Berkshire pigs are notoriously laid-back and easy going, making them ideal for first-time pig owners. Kunekune and American Yorkshire pigs are also friendly and easy to handle. 

Common Reasons an Aggressive Pig may Bite People

There are four common reasons for pigs biting humans. Pigs usually bite people out of fear, aggression, dominance, or boredom. Pigs can accidentally bite when exploring new objects, such as something in a pocket, zippers, or buttons. Additionally, pigs may bite because of feed-related behaviors such as hand-feeding or food rationing.  

Pigs Bite Out of Fear

Pigs are prey animals and, as such, are usually fearful of humans, especially while they’re still young. Pigs have few natural defenses and often turn to biting to protect themselves from a potential threat. If your piglet is biting you, ignoring it is usually an effective punishment. Turn your face away from it. Avoid hand feeding your piglets. 

Pigs Use their Mouths to Explore New Objects

Pigs in sterile enclosures that lack any environmental enrichment are liable to explore every new item with their mouths. Pigs don’t have hands to feel items so their mouths are the best way for them to understand their world. Unfortunately, this may include their handlers.

This isn’t as much of a problem with pigs that are kept in pens with entertainment, variety, or natural stimuli. Trees, bushes, even changing weather provides stimuli to pigs. 

Food-Related Aggression can Lead to Biting

This type of pig aggression is more common in house-trained potbellied pigs than in those living in commercial farming environments. Feeding your pig by hand, like you would a puppy, causes the pig to feel insecure about its food. Feeding pigs by hand may cause them to become greedy and start biting to secure more food.

It’s better to provide your pig free-choice access to food so that they can eat whenever they are hungry. This will help to prevent your pig from developing a scarcity mindset and becoming more aggressive around food. 

Pigs Bite to Establish Dominance

As pigs mature, they feel big and strong enough to establish themselves higher up the hierarchy. A house-bound pig may become territorial and attempt to establish dominance by biting other household members and visitors. The Most Aggressive Pig Breeds 

Although the wild boar can be highly aggressive, most domestic pig breeds are docile. Even domestic pigs may turn on a human in certain circumstances, however.

Examples of Aggressiveness in Lactating Sows

A few years ago, one of our Yorkshire sows gave birth to a large litter of piglets. Within their enclosure was a large tree branch which we had placed there to enrich the environment. 

Unfortunately, one of the smaller piglets became stuck in the fork between two branches. As it was squealing, I went in to help free its wriggling body. Sadly, the mother perceived my actions as aggressive and responded accordingly. 

When I slipped in the mud, the sow was instantly on top of me, her foaming mouth inches from my head. Her sharp hooves dug into my back as she trampled me. Luckily, I managed to wriggle out from underneath her, sustaining nothing more than a few bruises.

This aggression, clearly sparked by her strong maternal instinct, was highly uncharacteristic and quickly forgiven. 

I’m not the only one to experience such an ordeal; others have been less fortunate. A case study published in the journal Forensic Science, Medicine and Pathology described a situation in which a 49-year-old man was found dead in his farm’s pigsty. 

He had sustained numerous blunt force injuries and “massive upper extremities injuries” that led to such severe bleeding that he lost his life. 

Stop Pig Aggression Now

While specific individuals may be aggressive initially, the following management techniques can help you reduce the risk of violent conflicts. 

Stop pig aggression by socializing piglets to people early. Reduce your pigs’ stress levels by avoiding overcrowding. Provide pens that allow pigs to share critical resources such as food, water, or shade and to explore their surroundings. Establish your dominance early by responding to your pig firmly, but never aggression or threats. Do not scare your pig, but use a training board to create boundaries when training your pig. 

Early Socialization Reduces Violent Conflicts

Exposing piglets to early socialization with people improves their social abilities and reduces the frequency of aggressive encounters in later mixing events. 

You can also curb a pig’s aggressive instincts by minimizing changes to the social structure. Dr. Turner recommends avoiding regrouping pigs whenever possible. This stresses pigs out and changes the social hierarchy. If changes to the social structure are necessary, it’s better to do this as early as possible.  

Providing feed ad libitum during reorganization can also reduce the frequency of aggressive conflicts.

An Enriched Environment Reduces Boredom and Aggression

Pigs are natural foragers digging in the earth to uncover roots and other underground delicacies. Providing a substrate for your pigs to forage helps alleviate boredom and encourages natural behaviors. 

You can provide additional stimulation by adding enrichment materials to their enclosures. Rubber boots, hoses, balls, and chains can help keep your pigs occupied and reduce the potential for conflict.  

Overcrowding can Exacberate Pig Aggression 

Enclosed in a small space, pigs will fight over the best spots, especially in very cold, wet, or hot weather. Providing ample space and suitable shelter for your pigs will prevent stress and reduce aggression. 

Nutrition and Diet can Reduce Aggression

Studies indicate that low protein diets can increase the frequency of hostile behavior. Similarly, supplementing your pigs’ diets with tryptophan can reduce aggression in weaners. 

Increasing the protein content and frequency of food provision helps reduce unwanted behaviors and aggression. 

Access to Critical Resources Keeps Pigs Calm

Dominant pigs will attack others to protect critical resources like food, shelter, wallows, and shade. Therefore, if you provide sufficient resources for the herd, acts of aggression should decrease. 

That means ensuring pigs have access to enough food. Pigs are also calmer when allowed to choose between various feeds. 

Access to shade, water, and wallows is critical, especially in hot weather, when pigs are susceptible to heat stress. 

Building Trust will Help your Pig to Relax

Pigs use aggression to protect themselves against potential predators. If your pig perceives you as a threat, it’s more likely to be aggressive. Establishing trust reduces that aggression and creates a safer handling environment.

You can establish trust with your pig by speaking to it softly. Move slowly but purposefully and reward your pigs with treats and tidbits. 

If your pig backs away from you, give it more space. Allow your pig to approach you, encouraging it with tasty treats. 

Don’t raise your voice or move quickly, as this may startle the pig and provoke an aggressive response. 

Dominance Helps Create a Safe Handling Environment

Although you don’t want to frighten or intimidate your pig, you do want to establish yourself as a dominant member of its social hierarchy. 

Within the herd, dominant pigs use space to establish their superior status. They will step into the personal space of lower-ranking pigs, forcing them to yield and move away.

Replicating this behavior will help you establish a higher rank within the social structure. 

Move towards your pig slowly, entering its personal space. Watch his reactions to your proximity. If he moves away, he’s already subordinate to you. However, if he moves into your space, he’s crossed the line and is trying to establish himself as the dominant leader. 

Using pressure, you can teach your pig to respect your personal space. If your pig is already showing signs of aggression, you may need a livestock sorting board to protect yourself during training. 

If your pig moves toward you, apply more pressure. Move confidently towards him while giving a vocal command to back up. You can reinforce this by clapping or stomping your foot. The moment your pig shows any signs of submission or begins to move away, release the pressure and reward him.

Breeders Should Develop Low Aggression Genetic Lines

Studies show that aggressiveness in sows is a heritable trait. Breeders may select aggressive bloodlines inadvertently in the effort to create highly productive genetic lines.

However, aggression negatively impacts pigs’ welfare and productivity, especially among sows. Therefore, researchers recommend that pig breeders try to “develop low aggression genetic lines.”

This approach to breeding will facilitate group living for these social creatures without damaging productivity or profitability.


Pigs are naturally aggressive, using conflict to establish dominance within their social structures. Too much aggression is bad for their welfare and potentially dangerous for their handlers.

The tips in this article will help you provide the social and physical environments required to reduce aggressiveness and create a safe environment for both your pigs and yourself. 

Nicky Hoseck

I’ve been around horses since the age of six and, 15 years ago, leapt at the chance to leave behind my London-based career in journalism and start life on a small-holding in South Africa. Sharing my experiences with horses, goats, and other farm animals allows me to flex my writing skills and help others find their way to a happy, healthy herd.

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