Sudden Changes in Dog Behavior

You thought you could read your dog like a book. Seemingly overnight, he's not the consistent canine you know and love. If he displays sudden behavioral changes -- whether aggression, fear, house soiling or other issues -- something is wrong. Getting to the bottom of it means your dog might need to see a veterinarian, canine behavioral therapist, or both.

Aggressive dog
If your once outgoing dog now wants to hide, find out what's causing the temperament change.
credit: MarcinSl1987/iStock/Getty Images

Lifestyle Changes

If your dog's sudden behavioral change corresponded with a change in lifestyle, that could be the trigger. A move to a new house, a new baby, loss or gain of a pet in the household or change in the family structure causes stress in canines. Even if no such obvious change occurred, is your dog's daily routine different in any way? Dogs like structure and familiarity. If your vet rules out any physical reasons for your dog's behavioral change, ask her to recommend a canine behavioral therapist.

Older Dogs

Aging dogs suffer from some of the same behavioral changes as aging people -- including the onset of dementia. Common behavioral changes in elderly canines include house soiling, sleep pattern disruption -- such as walking around and vocalizing at night -- sudden fears, clinginess, separation anxiety, aggression and compulsive, repetitive actions. Take your old dog to the vet for a complete physical examination, and let the vet know of any changes in the household and all incidents of strange behavior. Depending on the results of blood and other tests, your vet might prescribe medication to help alleviate any cognitive dysfunction or anxiety. If your dog is diagnosed with a medical condition and his behavior is due to pain and discomfort, your vet might prescribe drugs or other therapies to treat the underlying disease.

Adolescent Canines

Dogs hitting the adolescent stage of life -- between the ages of 6 months to 1.5 years, depending on size and breed -- are the most likely to end up in shelters because of behavioral issues. However, those "sudden" behavioral changes from adorable pup to chewing, destructive, hyperactive canine are really stages, and will pass. If you don't intend to breed your dog, this is the time to have the animal spayed or neutered, which will cut down or eliminate aggression or sexually related behavior. Take your dog to obedience school and make sure he has plenty of exercise, mental stimulation and good socialization opportunities. Once your dog is fully mature, the two of you are headed into the best part of your lives together.

Thyroid Disease

Your dog's thyroid glands, located on either side of his trachea, produce hormones that regulate his metabolism. When the thyroid glands go out of whack, all kinds of symptoms result. In dogs, hypothyroidism, or inadequate hormone production, is far more common than hyperthyroidism, or too much hormone production. Typical behavioral changes in dogs lacking sufficient thyroid hormone include fearfulness, irritability, anxiety, compulsion and mood swings. The good news is that most of these symptoms are reversible when your dog is diagnosed as hypothyroid and receives daily medication.