Definition, victims and facilitating factors of severe dog on dog aggression (research article summary)

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Schilder, van der Borg, Vinke – 2019 – Intraspecific killing in dogs: Predation behavior or aggression? A study of aggressors, victims, possible causes, and motivations (link to partial view here) – Jnl Vet Beh Vol. 34 Nov-Dec 2019, pp. 52-59 

The University of Utrecht’s team of dog behaviour specialists has had another noteworthy article published. You can find our summary below. For copyright reasons, we are limiting our summary to information that is freely available in the article’s abstract. 


They analysed incidents for 151 dogs referred to the Veterinary Behaviour Clinic team for killing or seriously wounding another dog in the Netherlands. They also analysed data from 128 seized dogs, involved in serious dog-on-dog attacks. The analysis data was obtained from diagnostic interviews, behaviour tests and police reports. 

Important concepts

  • “Normal” dogs (i.e. behaviourally sound) are conciliatory creatures. They resolve conflicts ritualistically (body language and superficial bites), rather than causing actual injury. In other words: dogs tend to be all bark and no teeth. 
  • The team studied “dog-killing aggression”, meaning, in contrast with ‘normal’ dog conflicts:
    • Vigorous (as in: relentless, intense, uninhibited) attack
    • Fast attack (as in: lacking in the usual escalation in tension)
    • Without warning 
    • (Note: It does not necessarily result in the death of the victim, despite the name. “Dog-killing” is just the diagnosic terminology)

Aim of the study

Identify types of aggressors, types of victims, and possible underlying factors including motivations. 


  • Aggressors:
    • No single breed was prominent.
    • In the subcategory of seized dogs (not all dogs were seized by the police. Some of the dogs were simply referred to the clinic), 56% of the dog-killing dogs were of AmStaff/PitBull type. It would be hasty to conclude a genetic predisposition as this may also lie with owner traits. 
  • Victims: 83% were small-sized dogs 
  • Motivational factors and influences: Do take this with a pinch of salt, as, for the large majority of seized dogs, no information was available about the dogs’ past. 
    • About 1/4 aggressors had previously been seriously attacked by a dog themselves. 
    • Insufficient socialisation to other dogs only came out with 14% of analysed aggressors
    • Particularly strong predatory tendencies (not necessarily to dogs) only came out with 6% of analysed aggressors  
  • Specialists and generalists:
    • Specialists: Aggressors who only attack the type of dog with whom they had a negative experience.
    • Generalists: No pattern can be distinguished in these dogs’ victims. You could say they are “equal opportunity” attackers

Take-home points

(OhMyDog’s take, not necessarily the authors’ take) 

  • Be wary of any tense body language between playing dogs, particularly if one dog is much larger than the other
  • The (preventive) influence of a careful dog-on-dog socialisation as a puppy on this problem is unclear. Do not assume your dog is ‘immune’ to developing a severe dog-on-dog aggression problem because he was socialised to dogs as a pup. 
  • These attacks may not be predatory in nature, as was previously thought. Many may be facilitated by a past trauma from another dog.
  • As a dog behaviour specialist, obtain detailed and complete information about past incidents, follow validated testing protocols, and diagnose rigorously – without jumping to conclusions. Based on facts.   
  • And, for all owners: DO NOT LET THE DOGS SORT IT OUT! Your dog might fall victim to a serious attack, or might later become an aggressor.  

Dog on dog play: cheat sheet

To help you intervene early (recognize early signs of tension and inappropriate play) and appropriately (teach your dog an excellent recall by following an obedience course), OhMyDog has created a hand-out showing you when to intervene. Print it and take it with you to the dog park: 

  1. In Dutch
  2. In English


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