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Sharon L. Crowell-Davis,
DVM, PhD, DACVB
Department of Anatomy
and Radiology
College of Veterinary Medicine
The University of Georgia
Submissions can be sent to
Beth Thompson,VMD, via email
bthompson.vls@medimedia.com,
mailVeterinary Learning Systems
780 Township Line Road
Yardley, PA 19067,
or fax 800-556-3288.
Column Editor
Understanding Behavior
Aggressive Dogs:Assessment and
Treatment Considerations*
Sharon L. Crowell-Davis, DVM, PhD, DACVB
a
The University of Georgia
When a family presents a pet, especially a dog, for a history of aggression, an accurate
diagnosis is critical, and the potential for harm to other animals or to humans makes a
comprehensive understanding of behavioral diagnostics essential. However, diagnosis
and treatment of aggression present special challenges, and general practice veterinari-
ans need to be aware of not only the possible motivations, targets, and risk factors for
aggression but also the need to appropriately inform the client of the limitations of
treatment, the risk to household members and to others, and when to seek advice from
a behaviorist. Safety issues are a prime consideration if the family chooses to pursue
treatment rather than euthanasia.
All animals can cause harm, even as part of normal behavior. This article addresses
canine patients with a history that shows that, under certain circumstances, they will
cross the boundary of “may be aggressive” into “definitely will be.”
DIAGNOSTIC CONSIDERATIONS
A common error is to assume that dominance is the underlying motivation for
aggression. True dominance aggression directed toward humans is, in fact, very rare. It
is slightly more common toward other dogs, but interdog aggression occurs for many
reasons other than dominance issues and should not be assumed to be the underlying
cause of dog fights. Fear is a much more common cause of aggression, especially toward
humans. Dogs may also be afraid of other animals or inanimate objects, which can
cause confusion and an incorrect diagnosis in some cases. For example, if a dog is afraid
of the bathtub, it may become aggressive toward humans who put it in the bathtub,
even if it is not aggressive under other circumstances. Other possible types of canine
aggression include territorial, redirected, sexual, protective, possessive, and predatory
aggression. In all cases, it is important to identify the circumstances in which the dog is
aggressive to help diagnose the motivation for aggression. A careful history may reveal
that aggression is associated with a specific place or item (e.g., the house, a toy, food).
Animals may have more than one type of aggression. The box on page 275 provides
some resources that may help in the diagnosis of canine aggression.
As with other types of behavior problems, before any type of aggression is diagnosed,
the veterinarian should perform a thorough physical examination and conduct tests as
indicated by the dog’s age, behavior, and clinical signs (e.g., blood chemistry, complete
blood count, thyroid function tests, radiography) to rule out medical causes of aggres-
Send comments/questions via email
editor@CompendiumVet.com,
fax 800-556-3288, or web
CompendiumVet.com.
COMPENDIUM 274 May 2008
AboutThis Column
Behavior problems are a signifi-
cant cause of death (euthanasia)
in companion animals. While
most veterinary practices are
necessarily geared toward the
medical aspect of care, there
are many opportunities to bring
behavior awareness into the
clinic for the benefit of the pet,
the owner, and ourselves. This
column acknowledges the
importance of behavior as part
of veterinar y medicine and
speaks practically about using it
effectively in daily practice.
*Feline aggression toward humans and other cats was the subject of two previous columns:
“Human Feet Are Not Mice: How to Treat Human-Directed Feline Aggression” (August 2007)
and “Intercat Aggression” (September 2007). All Understanding Behavior columns are archived
at compendiumvet.com.
a
Dr. Crowell-Davis discloses that she has received financial support from CEVA Animal Health
and from Merial.
s
ive behavior, such as pain, infectious disease, occult
injury, or neurologic disease.
RISK ASSESSMENT
Over the years, I have often heard the comment that
the best thing to do with aggressive dogs is to euthanize
them—all of them. However, if this were our approach,
then most or all dogs would be euthanized. If an 11-
year-old miniature poodle with arthritis growls and
snaps without making contact with flesh, it has shown
aggression. In this particular case, treating the pain of
the arthritis and teaching the owners to manage the dog
so that they do not cause it to experience pain is a rea-
sonable approach. In my opinion, euthanasia would not
be indicated.
Lumping all aggressive dogs together is clearly too
simplistic an approach. While all dogs have the potential
to be aggressive and even to bite, some clearly present a
greater risk to public health than others. Assessment of
risk factors, therefore, plays a crucial role in deciding how
to treat an aggressive animal and whether to refer it to a
behaviorist.
Categorizing Aggression
As part of assessing risk, the veterinarian should try to
ascertain whether the dog is aggressive toward a particu-
lar group. Does it threaten only other animals? Is it
aggressive solely toward strangers? Does it snap at or bite
its owners? Does it chase children? In general, animals
that are aggressive to their owners pose a greater risk of
causing harm, as their owners may be unable to manage
them to prevent them from biting strangers. Likewise, if
a dog is aggressive toward children and there are children
in the household, the risk for harm increases.
Animal Risk Factors
Several factors relating to the dog itself affect its
potential to cause harm. Size is one. Large dogs, by
virtue of their weight, tooth size, and jaw strength, have
a greater potential to cause serious injury or death than
do small dogs.
The type of aggression is also relevant to an animal’s
potential risk for causing harm. A dog with fear aggres-
sion toward humans may present a risk for causing harm
only if someone corners it or reaches for it. While it is
incumbent on the owners of such a dog to ensure that it
is not allowed into a situation in which a naïve person or
a stranger might inadvertently trigger a bite, knowledge-
able owners may be able to maintain fear-aggressive dogs
with little chance of injury simply by avoiding behaviors
that might trigger aggression. Even if such an animal is
outside, it is likely to avoid encounters with strangers. In
contrast, a dog with territorial aggression is likely to
present a greater risk for causing harm, simply because it
may approach and initiate aggressive interactions with
strangers who enter, or attempt to enter, its perceived ter-
ritory. Confident dogs that have a history of approaching
and pursuing individuals who enter their territory proba-
bly present a greater risk for causing harm than dogs that
are both fearful and territorial. The latter are often more
likely to stand and bark at “invaders” and will bite only if
a person approaches them and initiates interaction.
The historic intensity of the aggression is also rele-
vant. Any dog may escalate its aggression, but those with
an established history of inflicting penetrating bite
wounds have demonstrated that they definitely will bite
if the right conditions are met. While it is impossible to
make exact predictions, especially given the variety of cir-
cumstances in which bites occur, a dog that has inflicted
multiple penetrating bites during aggressive interactions
is probably more likely to cause harm in a future aggres-
sive interaction than a dog that has historically exhibited
inhibited bites or snapping at the air. Likewise, a dog
with a history of biting deeply and repeatedly in a single
encounter probably represents a much greater risk for
causing serious harm than a dog with a history of taking
a single, quick nip and backing off from the situation.
The dog that has historically exhibited inhibited biting
in a given circumstance is, nevertheless, probably more
likely to cause harm if placed in that circumstance again
than is a dog that has responded in an entirely nonag-
gressive fashion (e.g., presenting a play bow).
Human Risk Factors
When the type of aggression has been diagnosed and
appropriate treatment is being recommended, special
Aggressive Dogs: Assessment and Treatment Considerations 275
May 2008 COMPENDIUM
• Horwitz D, Mills D, Heath S, eds. BSAVA Manual of
Canine and Feline Behavioural Medicine. Quedgeley,
Gloucester: British Small Animal Veterinary
Association; 2002.
• Landsberg G, Hunthausen W, Ackerman L.
Handbook of Behavior Problems of the Dog and Cat.
2nd ed. Edinburgh: Saunders; 2003.
Recent Books on Diagnostics and
Treatment of Aggression
COMPENDIUM May 2008
276 Understanding Behavior
consideration must be given to the presence of vulnera-
ble people, such as children, elderly adults, or disabled
people, in the household. If the day-to-day management
of a dog with fear aggression can be accomplished only
by healthy, competent adults, the presence of young chil-
dren or an elderly parent with Alzheimer’s disease can
be highly problematic. Young children may be incapable
of understanding that an aggressive dog must be left
alone or there will be serious consequences, while an
elderly parent may not remember that approaching the
dog may, in certain circumstances, cause it to bite.
Clients who own dogs that present a risk of aggression
to especially vulnerable people in the household are
probably best referred to a specialist.
TREATMENT CONSIDERATIONS
Permission to Treat
If, after a thorough risk assessment has been con-
ducted, the owners of an aggressive dog choose to
attempt treatment, the veterinarian must decide whether
to undertake treating the animal or to refer it to a
behaviorist. In either case, the owners must understand
that, just as it is impossible to guarantee that a patient
will survive surgery, no matter how minor or major the
procedure, it is impossible to guarantee that a dog will
not bite. It is important to make sure that owners are
aware of this and of their personal responsibility to
make sure that the animal does not have the opportu-
nity to bite or is not placed in a position in which it is
likely to bite. At The University of Georgia, before a
consultation regarding an aggressive pet is initiated,
c
lients are required to read and sign an “authorization to
treat” form (see the form on page 277) that was devel-
oped in cooperation between the university’s behavior
service and office of legal affairs. This form addresses a
number of pertinent issues.
Legal Liability
Both owners and veterinarians should also be aware
that aggressive pets raise issues of owner liability as well
as practice liability. I refer clients who have particular
questions relevant to their own liability to their attorney.
While veterinarians knowledgeable in animal behavior
can diagnose and offer advice regarding treatment of
aggression, they may not be aware of local laws regard-
ing owner responsibilities (e.g., restraint or “vicious ani-
mal” laws), especially if their clientele comes from a
wide area with varying local ordinances. It is the owner’s
responsibility to be aware of local laws regarding pets.
One issue of local and state law with which veterinari-
ans should be familiar pertains to the risks a pet presents
to children or other parties. If the pet presents a serious
danger to a child or other person and the adult owner acts
irresponsibly in supervising the pet, what responsibility, if
any, does the veterinarian have to report the situation, and
to what agency? Veterinarians should consult their own
legal counsel regarding their personal and practice’s liabil-
ity when it comes to handling aggressive animals.
Treatment Methods
A full discussion of how to treat the various types of
aggression is beyond the scope of this column. However,
I will touch on some aspects of treatment that should be
kept in mind.
An accurate diagnosis of the reason for the dog’s
aggressive behavior is critical. Attempts to treat aggres-
sion can have undesirable consequences if the motiva-
tion for the aggression is misdiagnosed. For example, if a
dog has fear aggression but dominance aggression is
diagnosed, instructions to “dominate” the animal or
“teach it who’s boss” are likely to produce two counter-
productive results. First, fear aggression is generally
exacerbated, not improved, by attempts to dominate an
animal. Thus, treatment plans designed to treat pre-
sumed dominance in a fearful dog actually cause harm
to the patient, making its behavior problem worse. Sec-
ond, confronting a fearful animal is likely to provoke a
bite. Even if the dog has true dominance aggression,
simple instructions to “teach it who’s boss” are likely to
be counterproductive. The rare, true cases of dominance
• Diagnosis and treatment of dogs with aggression
problems require a thorough behavioral and medical
e
xamination and a comprehensive understanding of
behavioral diagnostics and treatment protocols, as
errors in diagnosis or treatment can result in human
injury and injury to other animals.
• Breed, size, type and severity of aggression, and the
owners’ ability to avoid situations in which their pet
might be aggressive affect the public health risk that a
given animal represents.
• Special consideration must be given to the presence
of vulnerable individuals in the animal’s environment,
especially children, disabled persons, and elderly
persons. A dog with aggression that may be
manageable by healthy adults may present a grave
risk of harm to these individuals.
Key Points
Aggressive Dogs: Assessment and Treatment Considerations 277
May 2008 COMPENDIUM
Authorization to Treat
Name of Animal __________________________________________________________________
Case No. ________________________________________________________________________
I certify that I am the owner of the above-described animal. I have brought my pet to
__________________ [clinic name] for advice on decreasing its aggressiveness.
I understand that aggression by animals can cause injury, including fatal injury, to other animals, to
other people, and to me. I understand that treatment for aggressive behavior is an inexact science, and
it is impossible to ensure that my pet will not cause harm in the future.
I understand that the only way to ensure that my pet will not cause harm in the future is to euthanize it.
I understand that if I do not euthanize my pet, it will be my responsibility to take appropriate pre-
cautions to prevent my pet from causing harm. These precautions may include, but are not limited to,
informing persons near my pet of its aggressive behavior, keeping it on a leash and muzzled or with a
head collar, and/or keeping it restrained behind doors, gates, or fencing. I also understand that it is my
responsibility to be aware of and to comply with all state and local ordinances concerning aggressive
animals.
Finally, I understand that should I choose not to euthanize my pet and it causes harm in the future, I
may be held liable for such harm.
I hereby certify that I have read and understood the above and that I am signing this authorization
with the full understanding that the treatment of my pet may not eliminate its aggressive behavior.
Signature of Owner ________________________________________________________________
Printed Name ____________________________________________________________________
Date____________________________________________________________________________
Adapted from The University of Georgia Animal Behavior Service of the College of Veterinary Medicine.
COMPENDIUM May 2008
278 Understanding Behavior
a
ggression require careful handling and a gradual shift
in the owner–dog relationship without triggering harm
to either party. They are best referred to a specialist.
Incorrect assumptions about the motivation behind
aggression may also lead to use of inappropriate treat-
ment methods, such as flooding, in which the animal is
placed in the situation it fears and forced to stay there.
In the case of the dog that becomes aggressive because it
is afraid of the bathtub, an assumption that it is trying
to control or dominate humans may lead the owners to
place the dog in the tub and physically restrain it there.
Again, this can easily lead to a bite and exacerbation of
the fear. Appropriate treatment for this dog would
include progressive desensitization to the bathtub—not
to humans—and counterconditioning, perhaps com-
bined with use of appropriate anxiolytic medication. It is
extremely rare for flooding to be a safe and effective
treatment for animal behavior problems, although there
are a few exceptions to this rule.
Even if the reason for aggression is correctly identi-
fied, owners must be warned against attempting meth-
ods that are likely to lead to their injury. If the owners of
a dog that is aggressively excited by other dogs try to
flood their pet by leading it past other dogs while
restraining it, the owners are more likely to be bitten.
Circumstances that are likely to trigger aggression
should be avoided while the underlying motivation for
the aggression is treated. If a dog becomes aggressively
excited by seeing unfamiliar dogs and bites its owner
specifically because it is restrained on its leash at such
times (e.g., on walks), confrontations with other dogs
should be avoided. Instead, progressive desensitization
and counterconditioning to the sight of other dogs
should be conducted, and the dog should be walked in
locations and at times when uncontrolled encounters
with other dogs are less probable.
Use of a basket muzzle during the early phases of
treatment may be useful. A correctly fitted basket muzzle
allows the dog to pant, drink, bark, and even eat treats
that are inserted through the mesh. However, if use of a
basket muzzle is deemed appropriate for the safety of
people or other animals, the muzzle should not be placed
on the dog only when potential targets for aggression
might be present. The dog should be gradually intro-
duced to wearing the muzzle and taught to associate it
with pleasant experiences, such as eating treats or engag-
ing in an activity it finds desirable (e.g., going for a
walk). (See “The Multispecies Household,” March 2008,
for a more detailed explanation of how to institute use of
a
basket muzzle.) Once the dog is accustomed to wear-
ing the muzzle on a regular basis, gradual introduction of
individuals the dog might be aggressive toward can be
initiated. While the owners may be tempted to flood the
dog rather than desensitize it because the muzzle will
prevent the dog from biting, desensitization is generally
a more humane treatment approach.
Medications are sometimes used effectively in the
treatment of aggressive animals. Their use should be
thoroughly studied and their potential benefits and risks
reviewed before they are administered. An in-depth
review of this topic is presented elsewhere.
1
REFERRALS
Any time clients wish to treat rather than euthanize a
dog with which a general practitioner feels unqualified
to work because the animal is refractory to treatment,
extremely complex, or simply too dangerous, referral to
a specialist is indicated. Board-certified veterinary
behaviorists are listed on the American College of Vet-
erinary Behaviorists’ Web site, www.dacvb.org. As with
other types of veterinary specialists (e.g., veterinary
oncologists), not every town has a clinic qualified to
treat these dogs, so the owner should expect to have to
travel to seek the best help available. If the nearest
board-certified veterinary behaviorist is prohibitively
far away, a second option is to contact the American
Veterinary Society of Animal Behavior. Although this
is not a certifying organization, a number of veterinar-
ian members have years of experience working with
such animals.
EUTHANASIA
Many factors affect the decision to euthanize. Ultimately,
it is up to the owner to make the decision; however, advis-
ing the owner on this difficult topic is the veterinarian’s job.
A major consideration is how much of a public health risk
the dog presents. If the aggression is severe, what is the risk
to the owners? How much risk of bodily harm does the
dog pose to the owners, to friends, and to strangers?
Before I discuss euthanasia with an owner, we have a
long, comprehensive discussion of the patient’s history,
current behavior status, and family dynamics, and once I
have formed an opinion of what potential dangers exist
if the dog is not euthanized, I explain them thoroughly.
Rather than recommend euthanasia per se, I usually
begin by pointing out the hazards of not euthanizing.
For example, I might tell the owner, “If you choose to
take your dog home and attempt to treat him, there is a
COMPENDIUM May 2008
280 Understanding Behavior
g
ood chance that he will bite you again. The next biting
incident may be more severe than the last one. Also, you
know he occasionally bolts out the door without his
leash on. If this ever happens again and he encounters
someone walking in the neighborhood, he may well
attack them and inflict multiple bite wounds.”
Some owners in such a situation are quite ready to
euthanize, even if it is difficult. However, if the owners
are strongly bonded to the dog or the dog is “nice” most
of the time and only occasionally dangerous, the
euthanasia decision may be very difficult, even if the
owners see it as inevitable. Leaving the owners alone to
discuss the situation for a little while is often helpful in
such cases. Occasionally, owners want to euthanize their
dog immediately and not risk taking it home. Others
like to take their dog home for a few days, especially if
they feel they can do so without harm and can manage
the bite risk for that time. In helping owners deal with
the closure of such a difficult decision, I recommend, if
possible, that they give their dangerous dog one last
“good day.” While making sure to avoid the opportunity
for a biting incident, they can give the dog its favorite
food, play its favorite game, and have a pleasant experi-
ence with it. Their regular veterinarian is involved in the
decision making, and, depending on what is necessary
for the case, plans are made for the euthanasia to be as
calm and untraumatic as possible for all concerned.
CONCLUSION
Animals do not bite for no reason, and any good
behaviorist can determine what provoked a specific bite.
In some cases, it may be a normal reaction to circum-
stances—if, for example, the animal is defending itself
against a real, physical attack. However, when aggressive
behavior is triggered by what humans perceive as a
friendly interaction (e.g., reaching out to pet a dog) or by
an event that humans do not perceive as direct interaction
at all (e.g., walking past a dog’s territory), it becomes criti-
cal for the veterinarian to accurately identify the motiva-
tion for the behavior and treat or refer accordingly if the
animal is to continue to be allowed to live among
humans. Veterinarians who advise owners with dogs that
have a history of aggression need to be aware of the many
types of aggression, the risk factors that must be consid-
ered before initiating treatment, the legal issues involved,
and the alternative of referring animals they cannot treat.
REFERENCE
1. Crowell-Davis SL, Murray T. Veterinary Psychopharmacology. Ames, IA:
Blackwell; 2006.
