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Why is My Younger Dog Attacking My Older, Sick Dog?

Some dog owners may stumble upon problems with their younger dogs attacking older, sick dogs. Many times, the owners are very concerned because the older, sick dog may not be able to defend himself and this can lead to serious injuries. Often, there is a history of the dogs getting along well for many years, up until the older dog started getting sick and weak which coincides with the onset of the attacks. What is happening here? Many dog owners may assume that there's sort of "survival of the fittest" phenomenon going on or that younger dogs "attack" just because they detect signs of "weakness," but there are chances that there may be other dynamics going on that may be missed when dog behavior is categorized under such broad umbrella concepts. This article will tackle some possible causes for scuffles and fights between younger dogs and older, sick and weakened dogs.

"Leave Me Alone" Signals

dog tongue flicks whale eye

As dogs get older, they may weaken and have mobility issues which can have an impact on their relationship with the other dogs. While when they were younger they could simply move away to remove themselves from a situation they weren't comfortable with, now they may be forced to use other more impactive forms of communication such as growling or snarling.

Physical ailments in older dogs may also lower their threshold for aggression making them more likely to choose aggressive behaviors over ritualized social signals meant to avoid conflict. An older dog who never had a problem with a young dog placing his paw over a shoulder in a rude yet, playful manner may now react aggressively due to arthritic pain. While many young dogs can adapt and learn to respect more the new boundaries set by the elderly pet, some young dogs may have difficulty coping with these changes affecting what was previously a predictable relationship, explain veterinary behaviorists Debra Horwitz and Gary Landsberg in an article for VCA Animal Hospital.

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"Arthritis can stimulate pain aggression. A push on the shoulders or the rump or a small child landing on a dog with arthritis or dysplasia may cause pain and could cause pain aggression." ~Karen Overall

Failure to Properly Read Dogs

old dog

Dogs often resolve conflict through facial expressions and body postures. Problems though may start when, on top of being weak, sick or having mobility issues, older dogs start suffering from sensory decline. No longer able to see well or hear well, these dogs may fail to properly read the social signals of younger dogs. Older dogs may also develop cognitive changes associated with Canine Cognitive Dysfunction which can also cause them to be "zonedout'" whichcan sometimes put them into conflicting situations when they fail to properly read social signals from other dogs and respond to them appropriately.

"Fighting of a younger dog toward a dog that is aging or ill may be a function of the inability of the older dog to respond with appropriate postures and signaling when interacting with the younger dog. This may lead to a change in their predictable relationship." ~Debra Horwitz, DVM and Gary Landsberg

Fighting Over Resources

dog brk

In some cases, the younger dog may reach social maturity (which generally takes place between the age of 12 and 36 months) and may attempt to change the way resources are handled. In this case, scuffles arise from the younger dog becoming more and more protective over resources. Everything may go smoothly when the older dog surrenders access to resources, but problems may arise when when the older dog fails to relinquish resources. Owners may unintentionally exacerbate the conflict by intervening and supporting the dog which is more "suitable" for surrendering access to resources.

Another dynamic that may occur is that the owners may baby the older dog more and more as he requires more attention and care due to medical reasons, evoking conflicts since the owner's attention may be also perceived as a "resource" to guard. According to a study on aggression in dogs of the same household conducted by researchers Kathryn Wrubel, Alice Moon-Fanelli, Louise Maranda, and Nicholas Dodman, the actions of the owner such as paying attention to one dog rather than the other, triggered aggressive behaviors in 46 percent of the studied pairs.

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"Challenges may be active and involve food, rawhides, toys, attention or access to any of the aforementiined, or passive and involve posturing and the ability to manipulate the trajectory and behaviors of the other dog." ~ Karen Overall

Signs of Illness

dog pain goes away at the vet

In some cases, vocalizations emitted by the older dog can be a trigger for a fight. It's not unusual for an older dog to yelp in pain from an orthopedic or spinal problem or whine repeatedly due to cognitive changes. In several dogs, these distressing types of vocalizations startle them causing them to become more alert and even rush over and check on the injured dog. To some young, easy-to-arouse dogs though, such vocalizations may cause them to get anxious which can lead to an attack to the older dog. In such scenarios, it's important to separate both dogs and have the older dog checked out for better pain control and management of neurological or cognitive disorders.

A young dog suddenly attacking an older dog despite the older dog not vocalizing may also warrant a thorough veterinary visit. The younger dog may be suffering from a medical condition that can cause behavior changes that evoke aggression (an example is hypothyroidism). There are also chances that the older dog may be suffering an undetected illness of which the younger dog may have recognized subtle signs of illness. Dogs have proven over and over to us that they can detect early signs of diseases in humans so it wouldn't be surprising if they could do the same with other dogs, even though their response may seem to us inappropriate based on context.

The Onset of Seizures

Some young dogs may attack older dogs when they are having seizures. Many veterinary hospitals witness this. A dog owners bring in a dog with bite injuries delivered by another dog while the dog had a seizure. In this case, there are chances that these dogs are simply responding to something that they cannot fully understand or something they somewhat find somewhat distressing or threatening. When a dog has a seizure, it can be a very scary experience to witness for dog owners, but dog owners understand what is happening when dogs most likely do not. If your older dog is prone to seizures and you have other dogs in the house, it's best to play it safe and confine your epileptic dog away from the other dogs.

"Even if your other dogs have never been aggressive toward your epileptic dog during a seizure, you cannot predict what will happen every time you are not present. "~ WB Thomas, Dipl. ACVIM Neurology.

What to Do

There is really no remedy against aging and the best approach is to implement management strategies so to keep the younger dog and older dog safe. Keeping both dogs together is risky as aggressive behaviors are more likely to to escalate rather than get better on their own. In feasible cases where there are good chances the older dog will recover from a temporary illness, it may be helpful to enlist the services of a professional trainer/ behavior consultants who uses positive reinforcement methods and can provide guidance on how to implement management techniques and help resolve the conflict through humane behavior modification.

Disclaimer: The above are just a few examples of the dynamics that may go on in a household of older dogs and younger dogs. If your younger dog is fighting with your older, sick dog, please play it safe and implement safe management techniques and/or consult with a behavior professional.


  • VCA Animal Hospital: Why would dogs fight with a familiar dog living in the same home?,retrieved from the web on July 10th, 2016
  • Clinical Behavioral Medicine For Small Animals, 1e1st Edition, by Karen L. Overall. Mosby; 1 edition (January 15, 1997)
  • Kathryn M. Wrubel, Alice A. Moon-Fanelli, Louise S. Maranda, and Nicholas H. Dodman (2011). Interdog household aggression:38 cases (2006–2007). Journal of the American Veterinary Medical Association, 238, 731–740

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