Dog aggression can be defined as unrestrained or violent behavior directed towards another entity (another dog or human). Dog aggression can be accredited to numerous factors like territorial protectiveness, defensiveness, fear, and social anxiety. The canine brain physiology makes it evident that the increased release of the hormone vasopressin is associated with aggression, while high levels of the hormone oxytocin reduce aggressive behavior and result in placid temperament.

The American Temperament Test Society (ATTS) conducts a temperament test for measuring the stability, shyness, aggressiveness, and protective instincts of various dog breeds. According to their findings, dogs with high passing percentages ought to be less aggressive than those with low passing percentages; therefore, canine temperament is usually inversely proportional to aggressiveness.

Apart from considering the temperament test percentage for estimating the aggression levels of each breed, associating annual fatalities or casualties like dog bites or attacks with specific canine breeds could also help put together the most aggressive dog breeds. As per the Centers for Disease Control and Prevention, there are around 4.7 million dog-related injuries recorded in the United States every year, and every 1 in 5 people require medical attention for dog injuries.

Both nature and nurture are two pivotal elements to consider before estimating the aggression quotient of any dog breed. Some dogs are intrinsically aggressive, and when they are exposed to a threatening stimulus or environment, they tend to get more hostile. While some dogs are bred to guide sheep herds, others are bred to be aggressive and are used for dogfighting. It is also important to understand that the aggression component significantly increases when the dog is larger in size, increasing the severity of harm inflicted upon the victim.

Our Methodology

We will be using a subjective methodology for our list of the 25 most aggressive dog breeds in America, considering data from various science direct journals and national forums like ATTS (American Temperament Test Society) and C-BARQ (Canine Behavioral Assessment and Research Questionnaire). The results were also influenced by the behavioral data obtained from registered members of the American Kennel Club (AKC). We will also be considering reports of injuries and fatalities associated with dog bites before ranking the 25 most aggressive dog breeds in America.

According to C-BARQ, a different magnitude of aggression is exhibited by the same dog breed towards strangers, the owner, and other dogs. Some dog breeds show elevated aggression towards strangers while other breeds are more hostile towards others dogs, out of competitiveness or possessiveness. A mean of the aggressiveness ratios is considered before ranking the aggressive breeds.

With this context in mind, let’s now begin our list of the 25 most aggressive dog breeds in America.

25 Most Aggressive Dog Breeds in America

25. Greyhounds

Greyhounds are commonly used for coursing games and racing. Increasing cases of fear and anxiety in greyhounds have resulted in various incidents of aggression in the recent past. As per the Canine Behavioral Assessment and Research Questionnaire (C-BARQ), 1.6% of the cases involving greyhounds were related to the snaps, bites, or attempts to bite a stranger or a dog. However, no cases of aggression towards the owners were reported as per the research.

24. Labrador Retriever

The Labrador Retriever makes it to our list of the 25 most aggressive dog breeds in America. According to the C-BARQ report, the probability of a labrador retriever to snap, bite, or attempt to bite a stranger equals 2.3%. In comparison, the likelihood of a labrador retriever attacking the owner and other dogs estimate 1.7% and 4.3%, respectively. In 2011, a Labrador retriever mauled a three-year-old boy resulting in severe facial injuries. Incidents like these reflect upon the importance of appropriate training of retrievers to avoid hostility and intemperate behavior.

23. Mastiff (English)

Mastiffs are giant muscular dogs that weigh approximately 130 pounds. This breed of dog is known to become violent quickly if not trained properly. According to the C-BARQ report, the probability of an English Mastiff to snap, bite, or attempt to bite a stranger equals 2.4%. On the other hand, the likelihood of Mastiff’s attacking their owner and other dogs equals 0.8% and 6.3%, respectively. In 2014, a 13-year-old boy got attacked by a Mastiff, resulting in severe injuries. Similar cases concerning the aggressiveness of the Mastiff also surfaced in later years, leaving multiple people injured.

22. Portuguese Water Dogs

The Portuguese Water Dog is at the 22^nd position on our list of the 25 most aggressive dogs in America. Interestingly, Ex-President Barack Obama owned two of these while he served in the White House. A Portuguese water dog’s probability of attacking a stranger equals 2.7%, while the likelihood of attacking the owner and other dogs estimates 0% and 6.7%, respectively. Expensive breeds like Portuguese water dogs experience great health benefits when given fresh pet food instead of canned.

21. Havanese

According to the  C-BARQ report, the probability of a Havanese to snap, bite, or attempt to bite a stranger equals 2.7%. At the same time, the likelihood of attacking the owner and other dogs estimate 0% and 4.1%, respectively.

20. Soft Coated Wheaten Terrier

The Soft Coated Wheaten Terrier makes it to the 20^th position on our list of the 25 most aggressive dog breeds in America. According to the C-BARQ report,  the Soft Coated Wheaten Terrier’s probability of attacking a stranger equals 4.2%. In contrast, the probability of attacking the owner and other dogs equals 1.9% and 16.2 %, respectively.

19. Akita

Akita is a strong, independent, and muscular breed that weighs almost 100 pounds. Akitas are generally considered to be very affectionate and well-mannered. However, they are defensive around strangers and can get aggressive due to their territorial instincts. According to the  C-BARQ report, the probability of an Akita to snap, bite, or attempt to bite a stranger equals 3%. In comparison, the likelihood of Akita attacking the owner and other dogs is close to 1% and 29.3%, respectively. The high probability of attacking fellow dogs could be accredited to their inherited sense of dominance and territorial protectiveness. In 2014, a well-trained Akita saved its owner from a bear attack, which shows how protective and dangerous they could be at the same time.

18. Shetland Sheepdog

Shetland sheepdogs are bred as working dogs. They usually don’t exhibit any aggression if trained with care. However, poor training and fear or anxiousness towards strangers could result in aggressive attacks. The ratio of such attacks seems to be increasing with each passing year. According to the  C-BARQ report, the probability of a Shetland sheepdog attacking strangers, their owners, or other dogs is the same, i.e., 3.5%. Shetland sheepdogs are unpredictable, and the fear creeping inside them could turn into aggression quite swiftly. Sheepdogs require experienced handlers.

17. Siberian Husky

Siberian Huskies belong to the Spitz family of dogs. They are highly energetic, which makes them useful as sled dogs. However, if this energy is not utilized efficiently in physical activities, negative energy builds up and results in aggression. Siberian Huskies usually attack children rather than adults. The probability of a Siberian husky to snap, bite, or attempt to bite a stranger equals 0%, while the probability of a husky attacking the owner and other dogs is close to 1.9% and 5.6%, respectively. Siberian Huskies have strong predatory instincts, which makes them extremely dangerous for small animals.

16. Airedale Terrier

Airedale Terriers are exceptional watchdogs that are intrinsically aggressive with strong hunting instincts. They only attack another person when they consider their existence to be threatening and more often attack other small animals. The C-BARQ report indicates that the probability of an Airedale Terrier attacking a stranger equals 4.5% in comparison to a 1.5% probability of attacking the owner.

15. Cocker Spaniel

Cockier Spaniel lands the 15^th position on our list of the 25 most aggressive dog breeds in America. These dogs can turn aggressive if not socialized from an early age. They also exhibit dominance when the trainer or the owner isn’t capable of controlling the training process. According to C-BARQ, the probability of a Springer Spaniel to snap, bite, or attempt to bite a stranger equals 4.7%. Surprisingly, the probability of Spaniel attacking their owner is higher by 0.9%. Cocker Spaniel has been responsible for 59 fatal attacks in the past 25 years.

14. Saint Bernard

Saint Bernard is an intelligent and protective dog breed. They are known as service dogs that would rescue the hikers lost in the snowy mountains. Weighing between 140 to 260 pounds, Saint Bernards can be dangerous if not appropriately trained due to the weight and inherent aggression. In 2016, a Saint Bernard attacked a woman leaving her injured with 40 stitches and a dislocated knee.

13. German Shepherd

Frequently used as working dogs in the police K-9 unit, German shepherds are known for their vigilance and attentiveness. They weigh approximately 100 pounds and are very protective of their owners. Most of the fatalities caused by German shepherds were when the dog was trying to protect the owner’s family. While the probability of a German shepherd attacking a stranger is close to 4.5%, the likelihood of an attack against the owner and other dogs equals 2.1% and 16.4%, respectively. From year 2005 to 2017, 20 people died due to attacks from German Shepherds.

12. Rottweiler

Rottweilers are massive muscular dogs that are bred to be guard dogs. According to Merritt Clifton Dog Bite Statistics, Rottweilers have been involved in 535 dog attacks from 1982 to 2014. In 2015, a woman adopted a Rottweiler, and three hours into adoption, she was killed by the dog due to previous abuse suffered by the dog.

In comparison, a five-month pregnant woman was saved by her Rottweiler from a group of men with knives that broke into her house in 2015. According to C-BARQ, the probability of a Rottweiler to snap, bite, or attempt to bite a stranger equals 4.8%, and the probability to attack the owner and other dogs estimate 1.0% and 7.6%, respectively.

11. Doberman Pinscher

Doberman Pinschers are highly intelligent and are often used as guard dogs. They attack strangers whenever commanded by the owner. According to C-BARQ, the probability of a Doberman Pinscher attacking their owner and strangers equals 1.4% and 5.6%, respectively.

10. Great Dane

Great Dane makes it to our list of the 25 most aggressive dog breeds in America. They are giant dogs that can become aggressive if not trained properly. There have been many casualties associated with Great Danes, especially to children and other animals. According to C-BARQ, the probability of a Great Dane to snap, bite, or attempt to bite a stranger equals 5.7%, in contrast to a 1.9% probability of attacking the owner.

9. Boxer

Boxer is an energetic and playful breed of dog, but they are considered dangerous due to multiple injuries associated with them. Almost 48 attacks from this breed have been observed from the year 1982 to 2012. If not trained properly, boxers can inflict harm to toddlers and other dogs. The probability of a boxer attacking a stranger equals 5.7%, and that of attacking other dogs equals 15.7%.

8. Australian Shepherds

Australian Shepherds make it to the eighth position on our list of the 25 most aggressive dog breeds in America. Shepherds need to have at least 12 hours of physical exertion, or they can become destructive and aggressive. Australian Shepherds rarely attack their owners; however, the probability of a stranger being attacked by them equals 6.2%.

7. Beagle

Beagles are pack dogs that consider themselves as the leader or alpha dog of the pack or household. Beagles can get aggressive in an attempt to assert their dominance against human beings. The probability of a Beagle attacking strangers and owners stands at an alarmingly high rate of 7.9%.

6. Border Collie

Border Collie is one of the sharpest dog breeds. Though border collies are not bred to kill the prey, they turn aggressive if the herd is threatened. The probability of a border collie to snap, bite, or attempt to bite a stranger equals 8.0%, while the probability of attacking the owner and other dogs estimate 1.8% and 13.5%, respectively.

5. Jack Russell Terrier

Jack Russell Terrier is a bold and clever breed of dog bred for fox hunting. They have a powerful jaw with straight pointed teeth, which can cause severe injuries to both humans and other dogs. Studies suggest that they are most likely to attack a human when they feel threatened. According to C-BARQ, the probability of a Jack Russel Terrier to snap, bite, or attempt to bite a stranger equals 7.7%. In comparison, the probability of a Terrier attacking the owner and other dogs equals 3.8% and 21.8%, respectively.