On 17 August 2026, a serious dog-on-dog attack occurred in the YOHO area of Yuen Long. A large dog weighing approximately 60 kg, which was off-leash and without a muzzle, caused the deaths of two small dogs weighing about 5 kg each within roughly 20 minutes. Video footage showed the large dog continuously gripping the victims by the neck and shaking them; multiple bystanders intervened but were unable to stop the attack. This article draws on existing peer-reviewed research to analyse the behavioural mechanisms that may have been involved and proposes evidence-based preventive measures.
1. The Scientific Basis of Predatory Behaviour and the “Predatory Sequence”
Dogs retain the predatory motor patterns of their ancestors. The classic sequence proposed by Coppinger and colleagues is: orient → eye/stalk → chase → grab-bite → kill-bite → dissect → consume.
In 2024, Broseghini et al. established a more objective ethogram of canine hunting behaviour based on 60 real hunting videos, organising the sequence into four functional phases: search → approach → chase → bite. The study noted that attacks by dogs on other dogs sometimes display characteristics “strongly similar to predatory behaviour.”
“Predatory drift” is a concept commonly used in clinical behaviour science. It refers to a sudden switch from social interaction (especially play) into the predatory sequence, triggered by specific signals such as the high-pitched screams, struggling, or rapid flight of a small dog. When there is a large size disparity, small dogs are more readily interpreted by large dogs as prey rather than conspecifics.
2. Research Evidence on Body Size and Aggressive Behaviour
Multiple large-scale studies show that the relationship between body size and aggressive behaviour is not simply “large dogs are more aggressive”:
- McGreevy et al. (2013), analysing C-BARQ data from 8,301 dogs, found that average breed height was significantly negatively correlated (p < 0.001) with various problem behaviours, including owner-directed aggression, dog-directed fear, and separation anxiety. Shorter height was associated with higher rates of problem behaviours. Body weight was negatively correlated with excitability.
- Duffy, Hsu & Serpell (2008), using C-BARQ surveys of more than 30 breeds, found that the most severe aggression was directed at “other dogs,” followed by strangers and family members. Small breeds such as Chihuahuas and Dachshunds frequently ranked among the highest in both human- and dog-directed aggression scores, whereas large breeds such as Golden Retrievers and Labrador Retrievers generally scored lower for aggression overall.
In other words, small dogs more frequently display aggressive behaviour, but when large dogs do attack, the disparity in size and bite force results in far more severe injury.
3. Behavioural Characteristics of This Incident
Based on publicly available information and video footage, the incident displayed the following features consistent with predatory behaviour:
- Extreme size difference (60 kg vs. approximately 5 kg) — a high-risk context for triggering predatory behaviour.
- Attack style: continuous gripping of the neck and shaking, consistent with the grab-bite / kill-shake phase rather than the brief, intimidating bites typical of social aggression.
- Lack of aggression toward humans: when bystanders intervened at close range, the large dog did not redirect its attack onto people, consistent with the “target-specific” nature of predatory behaviour.
- Sequential attacks: successive assaults on two small dogs within a short time, indicating a possible state of high arousal or predatory motivation.
Public information is currently insufficient to fully reconstruct the interaction that preceded the attack. If there was no prior play between the dogs, the incident is more likely to represent predatory behaviour triggered directly by prey signals rather than classic “play-to-predation drift.” In any case, the size disparity and the sustained neck-biting behaviour make predatory-related mechanisms a highly plausible explanation.
4. Evidence-Based Preventive Measures
Combining the above research with clinical observations, the following recommendations are made:
- Strict compliance with leash regulations Dogs weighing 20 kg or more must be securely restrained on a lead no longer than 2 metres in public places (Dangerous Dogs Regulation). Regardless of a dog’s usual temperament, large dogs should never be allowed to roam freely in areas with high pedestrian or dog traffic.
- Management of prey drive and size-difference risk If a large dog shows intense staring or chasing tendencies toward fast-moving small animals or small dogs, consider using a muzzle in public and provide professional impulse-control training. Avoid unrestricted chase-style play between large and small dogs.
- Early recognition and intervention Watch for sudden quietness, intense staring, forward body lean, or accelerated approach in a large dog. Immediately increase distance if these signals appear. Reliable “recall” and “leave it” cues are essential everyday skills.
- Social responsibility Proper control is not only a legal requirement but the most direct way to reduce tragedies. Dogs are the property of their owners, who also bear responsibility for the safety of the public and other animals.
5. Conclusion
The Yuen Long incident highlights the serious consequences that can result when large dogs lose control in public spaces. From a scientific perspective, the triggering of the predatory sequence and prey drive provides an important framework for understanding sudden fatal attacks by large dogs on small dogs. Body-size difference itself is not evidence of higher aggressive tendency (McGreevy 2013; Duffy 2008), yet once predatory behaviour is activated, the outcome is often far more severe than typical social aggression.
The core of prevention lies in responsible ownership and risk awareness: correct leashing, understanding one’s own dog’s drive characteristics, and avoiding high-risk situations. Only in this way can we enjoy harmonious coexistence between people and dogs while minimising the recurrence of similar tragedies.
