Sudden Changes in Dog Behavior

A grumbling stomach could have your energized dog sleeping all day.
i Sleeping Dog image by StylezInk from

From tucking his tail between his legs to greeting strangers with a showing of teeth, abnormal behavior in your canine friend may stem from a growling stomach or a jarring experience with other dogs. If medicine won't help, a guiding hand usually will, unless your pup is passing through puppyhood into adulthood.

Medical Problems

Whether your dog is a food-lover or child-lover, a chaser of cats or a chaser of his own tail, an undiagnosed medical problem can make him seem like he's not the same pup you've always known. If sick, some dogs eat less while others lay around all day like their lazy cat counterparts. The problem could stem from a simple cold or upset stomach. But because dogs can suffer from a slew of harmful medical issues, such as Lyme disease, it's impossible and harmful to diagnose a dog's condition on your own. If your barking friend seems to have less energy, but is otherwise acting normally, it's fine to wait a week to see if he improves. If he's not eating, has suddenly turned aggressive or has difficulty moving around, a trip to your vet as soon as possible will help get him back on his feet.

Traumatic Experience

Your dog might consider thunderstorms traumatic experiences, but a bit of noise won't result in a sudden behavior change aside from a quick run to find shelter. Traumatic experiences that involve another person or dog inflicting harm on your dog or vice versa can cause mild to severe short term or long term behavior changes. Most of the time, such changes result in a calm, tail-wagging dog displaying never-before-seen aggressive behavior, or a confident dog appearing fearful when strangers or dogs approach him. If your dog was only involved in a minor altercation, he'll often revert back to normal behavior after a week or two. If there was an all-out teeth-clashing fight, he may be out of whack for a while. Reestablishing your dog's confidence, through basic obedience, and using positive reinforcement so you don't promote fearful behavior, can help return the dog you've always known. If the behavior change is severe, professional trainers can work with your dog and help him.

Puppy to Adult

If your once naïve puppy has taken his first few steps into becoming an adult dog, his behaviors will change. The world around him and what he's been exposed to can prompt the change just as much as his breed's characteristics. If you've socialized him well and showed him that everything strange isn't big and scary, his environment won't cause a sudden behavior change. If socialization doesn't occur between your dog's first 4 and 14 weeks of life, your dog will likely appear scared of new dogs and people, possibly demonstrating fear-aggressive behavior, Purdue University College of Veterinary Medicine explains. Breeds that are more alert and aloof than others also demonstrate a change as they grow out of their puppy stage. German shepherds, for example, begin appearing cool and distant to strangers.

Introducing a New Pet

Many dogs can't believe you would have the gall to bring in a new furry friend. They often react atypically, lashing out at the intruder when they would never display that type of behavior before. A lot of the times, your dog is simply saying he was in the house first and the other animal will respect him. Your dog may also clamor more for your attention and appear extremely jealous when you talk to or touch the new pet. Separating the two animals when you leave, until they coexist with one another peacefully the majority of the time, prevents a potentially dangerous scuffle when you're not there.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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