Behavior
Behavior concerns are common in both dogs and cats. Veterinarians see pets with everything from thunderstorm anxiety to tail chasing.
Dogs can act in ways that can appear aggressive but the root cause for the behavior is fear. This is the most common cause for aggressive behavior but it is not the only one.
Some dogs will also guard different resources in the home and this can become a problem if the dog acts out towards other pets or people in the home. Resources can be anything from food to toys, even you!
Cats can also exhibit behavior concerns. The most common is inappropriate urination or urine marking. Urine marking is most common in intact 'Tom' cats when marking their territory. All cats can spray, however, including females. In neutered males or female cats, spraying is often caused by anxiety.
Sometimes, medical reasons can cause behavior changes and this can be overlooked. Endocrine diseases such as hyperthyroidism (cats) or hypothyroidism (dogs) can cause behavioral concerns as can pain. Urinary issues in cats are commonly caused by stress and a condition called interstitial cystitis and rarely an infection.
If your pet is suffering from behavioral trouble, it is wise to rule-out health concerns first with an exam and basic lab work. If all seems normal, further consultation with a veterinarian, a veterinary behaviorist, and a trainer will be advised.
Behavior consults are typically quite involved and will examine a pet's history, interactions with other pets as well as humans, diet and feeding routine, home life and possible changes, owner's routines and more.
The American College of Veterinary Behaviorists has some useful resources for owners with further questions.