Why Are my Two Dogs Fighting?


Two household dogs fighting can be very stressful for owners

I recently saw a very interesting case of two dogs in the household fighting with each other. The older dog is 5 years old and the owner has had him since he was 10 weeks old. The younger dog is 13 months old and has lived with the owner since he was 4 months old. According to the owner, the younger dog began to attack the older one about 4 months ago. Over a short time, the attacks increased in frequency to several times a day and were so upsetting to the owner that she explored the possibility of re-homing the younger dog. She saw our appointment as his last chance to stay in her family.

There are many reasons one dog may attack or be aggressive toward another: He may be guarding a very valuable resource (rawhide, toy, etc.) and think the other dog wants it. He may be of a breed that has been selected for dog aggression. He may have been poorly socialized to dogs. He may have had bad prior experiences with this particular dog.

But, for two dogs that live in the same house, the most common type of aggression is called “Dominance-Status Aggression” (DSA), also sometimes called “sibling rivalry.” In this setting, the dogs know each other well, and get along very well much of the time. Generally one dog is consistently the aggressor and the fights/attacks happen most commonly when the owner is present. Other possibilities for two household dogs fighting include pain/injury, illness, territorial aggression, or maternal aggression.

So, what causes DSA and what can be done about it?

Causes of DSA.

Usually, the owner is the cause. It is over-simplistic to say this; but, the reality is that the average dog owner will often completely ignore his dogs’ social hierarchy and attempt to impose what he believes to be equitable. This leads to tension between the dogs, which then leads to aggression when the owner is present.

What does it mean for dogs to develop a hierarchy? Speaking generally, dogs have a flexible but fairly strong social structure, in which one dog is the most dominant, followed by a more subordinate dog, then the next most subordinate, and so on. If you are watching a group of dogs that know each other well, you will see which one has easiest access to the best resources (toys, treats, lounging spaces, etc.); this is typically the most dominant dog in the group. The dog that most willingly gives up resources is generally the most subordinate. The others fall in line in the middle. This is a gross generalization (and some very subordinate dogs will fight for certain resources); but the principle is reliable.

Unfortunately, owners have their own sense of fairness. Usually, they give the older, more frail, or most beloved dog the best of the resources and the most attention, regardless of his status in the group. This is a perfectly human thing to do. Yet, if the owner chooses to lavish attention and resources on a less dominant dog, the more dominant dog may feel compelled to put the favored dog in its place, through growling, biting, or other aggressive act. The owner, who generally responds negatively (yelling, scolding, or other form of punishment) to the aggressor, may increase his attention on the attacked dog, thus escalating the problem.

What about two dogs that start fighting suddenly after having been “fine” with each other for months. If a younger subordinate dog is becoming socially mature or a previously-dominant dog is failing in health, there may be the opportunity for a shuffle in the dominance hierarchy. If the owner inadvertently lavishes attention on the wrong dog, there can be aggression as a result.

It should be noted that not all dominant dogs care enough to interfere with the owner’s interactions with the other dog.

Treatment of DSA.

Often, treatment is as simple as correctly identifying the dominant dog and supporting him as such. This is accomplished by giving him the most attention, providing him with better resources (nearer the owner on the bed or sofa, first access to the house or yard, etc.), and asking for less “work” (aka fewer commands) before giving him things. If the dominant dog has to sit for his dinner, the other dog must sit and shake paws before the food dish touches the ground. If a battle does break out, owners should leave the room, as their presence is typically required to fuel the conflict. Under no circumstances should either dog be punished for his actions.

If one or more of the dogs is unneutered, surgical intervention in the form of spaying or neutering can also help relieve some tension.

Owners are occasionally resistant to these changes, because they have been favoring the subordinate dog for a reason. But, when they see the difference their actions can make to the stress level in the house, they usually come around. They also get creative about spending quality time with their favored pet without the other being aware.

Challenging Cases.

Dominance within the hierarchy is determined by some combination of health, age, size, sex, and overall confidence. But, what if you have two dogs of the same sex from the same litter? You have two dogs that are likely equal in most factors that determine hierarchy. As they come to social maturity, one of three things may happen: If they are pretty mellow, they may never establish an obvious hierarchy and be perfectly willing to share the lead. If one cares more than the other, he may simply declare himself dominant without contention. Or, you may have a situation in which the two dogs spend their adulthood struggling for dominance, possibly without resolution. This is a particularly challenging situation for which there is no simple solution.

My Case

In the case I saw, the owner was amenable to making changes in the way she treated the dogs. She was not excited to reward the “upstart” in favor of her long-time companion. But she saw the merits. She also saw the tension between the two dogs melt away. One month later, the two dogs rarely scuffle and the owner is delighted.

Adventures with Osteosarcoma, Part III: The Adventure Ends

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Brick in his younger days, enjoying the great outdoors

I apologize for an extended absence from this space. Family obligations, a house purchase, and career changes are mainly to blame. In addition, on June 6, our dog Brick lost his battle with osteosarcoma. With chemotherapy, we were able to buy some extra time with him – most of it quality time.

In the end, Brick did us the honor of making it clear that it was his time to go. After all, no owner wants to waffle for long periods over the decision to euthanize. Trust me, no waffling was necessary that morning. We had been so focused on controlling his lung metastases that we were surprised when a spinal tumor (at T7) began to cause increased pain and, rapidly, the inability for Brick to stand or walk without assistance. Since he weighed nearly 100 pounds, assistance was not easy to provide, and his pain quickly became quite severe.

Brick was euthanized by his oncologist at the teaching hospital, where it is the custom for euthanized pets to be necropsied (autopsied) by veterinary students during in their pathology rotations. Having been through that service as a student – and knowing how difficult but important necropsies are for the learning process – I had no qualms about providing consent. The final pathology report was posted and I have mustered the courage to read it. By the time of his death, the osteosarcoma had reached his lungs, T7 vertebral body, thyroid glands, liver, kidney, spleen, and adrenal glands. The cancer had ravaged his body.

We are recovering, slowly, from our loss. My husband lost a best friend. I lost a wonderful companion that made me and our children rest better on those nights my husband travels. We still expect to see him at every turn, even after moving houses three weeks after he died. The kids are learning how to process such a life-altering event, while we adults realize that our grieving will take time.

On a much happier note, I soon begin a new professional chapter: next Monday (8/1), I become the newest behavior resident at UC Davis. It is a three-year program in which I will be trading flea treatments and radiographs for in-depth, probing appointments designed to help people with their unruly pets. Cases most typically involve some form of aggression, anxiety, or elimination issue. I will be treating mainly dogs and cats. While I would love to see other species, I think I may be limited to the occasional feather-picking cockatoo or cribbing horse.

I’m quite excited about this new opportunity and hope that some cool behavior cases work their way onto this blog.

Aural Hematomas in the Dog and Cat


Aural hematomas are puffy pockets of blood

I always thought that aural hematomas (blood pockets in the ear flap) were the curse of floppy-eared dogs. Then I saw one in a German Shepherd Dog. Still, I was sure that these annoying complications were limited to dogs – until I saw one in a cat. So, what causes these big, puffy blood pockets that owners despise so much?

How hematomas form: Many people are familiar with the concept of a blood blister, like the kind you get when you pinch your finger in a door or pair of pliers (or am I the only clumsy one?). Aural hematomas are very similar to these blood blisters. They form when an ear vein is damaged and leaks blood under the skin of the ear flap. The pressure of the blood against the skin causes a pocket to form, which allows more blood to leak from the vein. This vicious cycle continues, sometimes until all available space has been used, leaving the ear very puffy and heavy. At this point, pressure or trauma may cause a small opening in the ear flap, allowing blood to ooze, pour, or otherwise escape into the environment. More typically, however, the owner is able to get the pet veterinary care while the blood is contained. More

Urolithiasis: Urinary Stones

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Most bladder stones can be seen on plain x-rays.

This week, we had several discussions around the clinic about bladder stones in cats and dogs. I thought this might be a good topic, as these often take owners totally by surprise.

Urinary stones can form from many different inorganic compounds and can make trouble anywhere along the urinary tract. Common types include struvite (magnesium-ammonium-phosphate, sometimes still referred to as “triple phosphate”), calcium oxalate (“CaOx,” which come in monohydrate or dihydrate varieties), urate, and cystine. Struvite and CaOx constitute by far the majority of stones seen in cats and dogs. Each type develops based on fairly specific conditions, such as urine pH, the presence of bacteria (struvite in dogs), or a primary disease process (urate with liver disease). In addition, breed-specific mutations may permit large amounts of the precursor compounds that lead to stone formation; this is true of cystine (Newfies, Dachshunds, and English Bulldogs) and urate (Dalmatians). More

PU/PD Series: Acute and Chronic Renal Insufficiency

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The nephron, the functional unit of the kidney, can be damaged in many ways to cause renal insufficiency.

Along with all the other organs that can cause PU/PD (increased urination and drinking known as polyuria/polydipsia), the kidneys themselves are sometimes to blame. While renal disease is complex, it is important to understand some acute and chronic kidney problems that lead to PU/PD.

With acute or chronic insults to the kidneys, the ability of the kidneys to concentrate urine is lost; in most cases, the renal tubules that are responsible for drawing water back out of the urine, are damaged. The pet urinates out a higher percentage of water, thus diluting the urine and leading to possible dehydration. The pet drinks more water to counter this loss, and is officially PU/PD. More

PU/PD Series: Feline Hyperthyroidism

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Methimazole (Tapazole) is a typical first-line treatment for feline hyperthyroidism

One of the strange realities of veterinary medicine is that cats become hyperthyroid, while dogs become hypothyroid. Even stranger: some treatments for hyperthyroid cats may leave them permanently hypothyroid, which does not appear to cause health problems the way it does in dogs.

What causes it? Hyperthyroidism is caused when the thyroid gland overproduces thyroid hormones, either because it has a benign or malignant growth, or because it has undergone “adenomatous hyperplasia.” The latter is by far the most common cause and is a fancy way of saying “it got bigger and is producing lots of hormones.” The thyroid is a bi-lobed structure that sits on either side of the trachea; and the increase in size can affect one or both sides. More

PU/PD Series: Diabetes Mellitus

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Nearly all diabetic dogs and over 50% of diabetic cats rely on insulin given by their owners.

Diabetes mellitus is a fairly common cause of polyuria/polydipsia in cats and dogs. In nearly all diabetic dogs and over 50% of diabetic are dependent on insulin given by owners. In the other 30-50% of cats, the disease can be treated with diet, exercise, and oral medications. Either way, it remains a difficult disease to manage.

What causes it? Diabetes Mellitus (DM) results from a drop in the insulin levels in the body (or, in some cases, the body’s perception that insulin levels have dropped). Insulin is produced by the pancreas and, among other things, acts on the liver, muscles, and fat deposits to cause them to take glucose out of the blood and store it as glycogen or fat. If the ß cells in the pancreas stop making insulin – or receptors in tissues stop recognizing it – the glucose stays at high levels in the blood, can spill into the urine, and can create a multitude of health concerns that we associate with DM, including cataracts, glaucoma, urinary tract infections, weakness in hind legs, and life-threatening ketoacidosis. More

Marijuana Intoxication in our Pets

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Medical marijuana edibles are attractive to some pets

Although it’s not very common to see dogs suffering from marijuana intoxication, we dealt with two such cases in one day last week. I took that as a sign that it was time to discuss the topic.

In one case, a 6-pound dog had ingested two chocolate chip and pot cookies 10 hours before calling us. The other case was a 50-pound pointer that had eaten one pot cookie the night before we saw him. The owners of both pets were forthcoming with information about what their pets ingested, which was very helpful.

Clinical Signs: The active ingredient in marijuana, tetrahydrocannabinol (usually called THC), can cause loss of coordination, restlessness or sedation, dilated pupils, and slowed heart rate and breathing. Occasionally, the pet may lose bladder control. Clinical signs usually begin 30-90 minutes after ingestion. More

PU/PD: What It is and What Causes It

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Owners notice when they need to fill the water bowl more than usual

If you look at the daily schedule in a vet’s treatment room, you might see something like this next to the patient name: “K9: √ ears” (check for infection/irritation in this dog’s ears), “lag: ADR” (the owner of this bunny thinks it “ain’t doin’ right”), or “fel: Ⓥ” (this cat has been vomiting). These are all very useful shorthand notations that allow the vet to start thinking about how to approach the case before she enters the exam room.

Another very useful abbreviation is “PU/PD.” This is shorthand for a medical term: polyuria and polydipsia, which simply means urinating and drinking more than normal. There are many possible causes of PU/PD in cats and dogs; so it’s important to make a mental rule-out list that’s consistent with species, age, and other owner complaints, like vomiting or weight loss. The important thing here is to start with the “horses” (as in, “when you hear hoof beats, think horses [common diseases], not zebras [rare diseases]”). So, what are the PU/PD “horses” for cats and dogs and how do you diagnose them? More

Why is My Cat Peeing on my Bed?


Sometimes your cat turns his back on the litter box. But, why?

A cute little 7-year-old cat came into the clinic last week. She has a history of periods of inappropriate urination (she pees on beds and other furniture). The owner brought the cat to the clinic to rule out a urinary tract infection.

There are many possible reasons for a cat to urinate where it should not; some are primarily medical, some are primarily behavioral, and one is in between. The most common medical causes are urinary tract infection, bladder stones, bladder cancer, and orthopedic pain (like arthritis). Behavioral causes include territorial spraying/marking and rejection of litter box due to cleanliness, location, competition, or litter choice. One diagnosis that spans both categories is feline idiopathic cystitis (FIC; sometimes called feline interstitial cystitis). Our goal in these cases is to rule out the medical causes before we begin to explore the behavioral ones and FIC. More

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