Pets may poop on your bed for a variety of reasons, none of which involve what we humans call "spite."

A sudden change in a pet's behavior is often the first sign of a health problem. If the pet checks out as healthy at the veterinarian's, then consider any possible new source of stress.

Both cats and dogs may use urine and feces to mark territory when they are feeling threatened or stressed by changes in the environment or household routines.

Punishing your pet only adds more stress and continues a vicious cycle. Instead, look for ways to reduce your pet's stress by meeting more of your pet's needs. Establish a predictable daily routine for feeding, exercise and companionship. (Animal behavior experts Susan and Dr. Rolan Tripp are the authors of "On Good Behavior." For more information, visit their Web site at AnimalBehavior.net.)

Animal behavior experts Susan and Rolan Tripp are the authors of "On Good Behavior." For more information, visit their Web site at AnimalBehavior.net.