If your pet isn't acting normally then it may be an indication that something is wrong. Illness, stress, fear, and other things can cause a pet to act abnormally and being able to decipher what the reason for the change in behavior might be can be helpful to both you and your pet.
Your pet may be acting abnormally because it is not feeling well. Illness can cause a pet to not want to do the things it usually enjoys like eating and playing. Lethargy is a common sign of illness along with vomiting, diarrhea, and anorexia but more subtle indications may also be observed. Sunken eyes can be a sign of dehydration, sleeping in abnormal spots to seek warmth or cold can indicate your pet has an abnormal temperature, and not wanting to pick up toys may mean your pet has dental disease. Even aggression can indicate a hormonal problem due to an illness like hypothyroidism. If you suspect your pet is not acting normal because it may be sick, seek veterinary attention.
Stress and Anxiety
A change in your pet's environment can cause it to experience some stress and anxiety. This can be an intermittent thing or chronic depending but behavior changes are often the result. Aggression, inappropriate urination and defecation, reluctance to eat, hiding, and other things may indicate your pet is stressed or anxious. If you can make a change to eliminate the stressor then that's ideal but if not, pheromones, supplements, special diets, training techniques, and medications may be helpful to your pet.
If something has scared your pet, chances are it will act abnormally. Usually this is temporary and behaviors return to normal after the initial scare fades but sometimes a very traumatic incident or ongoing fear causes a more chronic change in behavior. You should never intentionally scare your pet but sometimes things that aren't typically thought of as being scary can startle your pet. Inappropriate urination and defecation, aggression, vocalizing, avoidance of an area, item, person, or other animal, and other behaviors may be triggered if your pet is fearful. Eliminating the cause of the fear is ideal but depending on the what has scared your pet and how severe of a fright it gave it, that may be impossible. Training and desensitization techniques, pheromones, supplements, and medications may be necessary.
While hormone changes can be a result of an illness, they also occur naturally as a dog or cat becomes sexually mature or is pregnant. Just like humans, pets may act differently if they suddenly have a surge in hormones. If your pet is about six months of age and has not been desexed or there is a chance it may be pregnant or have a false pregnancy, hormones may cause behaviors you haven't seen before. Mounting, humping, aggression, nesting, panting, and other behaviors can be signs that your pet has had an increase in hormone release. These behaviors are usually temporary, unless you have an unneutered male that smells a female in heat. In that case, the behavior may persist until the female is no longer nearby or it is no longer in heat. Spaying and neutering your pets can eliminate these behaviors.
If your pet has been injured or has a painful disease, it may not act normally. Pain isn't always obvious to detect. Pets can be very good at hiding things to avoid showing weakness so just because your pet isn't limping and crying doesn't mean it doesn't hurt. Internal trauma from an injury or illness may go undetected unless a thorough physical examination and sometimes other tests are performed by your veterinarian. Pain should not be ignored so you should seek veterinary attention if you think your pet may be in pain.
As pets age, brain function may begin to deteriorate just as it can in people. Staring off into space, vocalizing for no apparent reason, sleeping more, getting lost in its own house and other behaviors may be a sign that your older pet is experienceing some cognitive dysfunction or dementia. Various diets, medications, and supplements may support your pet as it ages and can be discussed with your veterinarian.
Some pets get bored more easily than others but if a dog or cat is restless and tired of having nothing to do, it may start to act differently. Working breeds of dogs and many cats are prone to boredom and may act out if they don't have an appropriate outlet for their energy. Providing pet puzzles at meal time, hiding toys and treats to encourage mental and physical activity, and regular exercise can help prevent boredom.
If your pet is acting abnormally, think back to when the change in behavior started. Try and see if anything coincides with the change to find the potential cause. If you are unable to figure out what might be causing your pet to not act normal, a visit to your veterinarian may be warranted.