It's probably safe to say a good many of your dog's behaviors straddle the line between normal and weird. And while you can ignore some behaviors, like his need to shove himself under your bed to sleep or drop his toys in his food bowl, unusual behaviors that suddenly appear or cause your pup harm are more troublesome.
If your pup has taken to eating paper towels, grass, dirt, toilet paper, wood chips, cat litter or even his own feces, that's unusual behavior that needs to be nipped in the bud right away. In the case of grass and dirt consumption, he might have a nutrient deficiency. Extreme boredom may cause him to hunt down toilet paper and eat pieces of your furniture. On the flip side, he may stay away from nonedible items but instead scarf down his food way too fast, eat too much dog chow or refuse to eat altogether. Appetite issues sometimes act as a harbinger of medical problems, and in other cases they're more behavior-related.
In a lot of cases, aggression is a long-term problem associated with a lack of socialization, poor genes or a bad past experience. But if your pup has turned from a relaxed and caring canine into a fierce barker and snapper in recent weeks and days, he may not be feeling well. Lots of medical problems can cause a sudden onset of aggression. Certain medications, such as corticosteroids, can also cause aggression problems. A change in your pup's daily life, through the introduction of a new animal or person or a shift in his routine, can upset him and trigger aggression.
With no bills to pay, no children to parent and no responsibilities of any kind, dogs have little that tires them out and keeps them down. They're usually running around and wanting to play games every day. When your pup's lethargic, he'll lie around most of the day and seem to have little motivation to engage in fun doggy activities. A bout of lethargy is almost always indicative of a medical problem or a side effect from medicine, from something as minor as an upset stomach to a serious bladder infection.
Sometimes canines seem to engage in odd behaviors compulsively, such as spinning, snapping -- also known as catching flies -- and excessive licking. One minute your little guy will be sitting on the floor tending to his stuffed monkey toy, and 20 minutes later he'll lick or bite at his stomach. Behaviors such as spinning and tail chasing aren't usually harmful to your dog unless they interrupt his daily life. But behaviors like licking and biting can bring about painful lesions, bumps and even cause infections. Certain events, especially stressful ones, like a scary thunderstorm or the evil vacuum cleaner, can trigger compulsive behaviors. But sometimes there's no known cause.
There's a reason plenty of pictures exist of couch cushions ripped open and stuffing lying next to the canine culprit: Dogs and especially puppies can be destructive. That in itself isn't unusual behavior. It often indicates your pup is bored. But if your pup's destructive tendencies just appeared out of the blue, or he's being extremely destructive and destroying his crate, ripping up your carpet or even hurting himself while he devastates your house, that's not usually the norm. Boredom can definitely be a factor, but so, too, can panic attacks, stress and separation anxiety.
Because medications and medical conditions cause so many unusual behaviors, always have a chat with your vet before doing anything else. If an illness or medication isn't the problem, it's probably a behavioral issue. In most cases, counterconditioning solves behavior problems. Counterconditioning involves determining the trigger of your pup's behavior and then slowly associating that trigger with something positive. You want your pup to think of the trigger as something that causes awesome things to happen so that he doesn't bark, charge the window, lick his paw or whatever doggy thing he does. Your vet or a qualified trainer can help you with counterconditioning. Do not try to countercondition an aggressive dog on your own.