1) Wagging tail equals happy dog
Of course, dogs do wag tail when they are happy or excited. But it is not always the case. It can also be sign of alertness, anxiety, fear or nervousness. If your dogs wagging its tail while running and jumping around, it is most likely happy. If its body is almost motionless and it only shakes its tail, it's likely that the animal is nervous or fearful.
2) Shaving longhaired dogs
Shaving longhaired or doublecoated dogs in hot weather might sound like a good idea, but it is really really not. It will not help the dog to cool down, quite the opposite. Shaving a double-coated dog can actually make it harder for him to cool off, because the dense doublecoat has the ability to insulate cold, but also hot temperatures. Instead of shaving, you should focus on regularly brushing your dog during hot days, which will remove all the unnecessary loose and dead hair and which will be actually beneficial to help your dog to cool down.
3) Hypoallergenic dogs
Speaking of coats, lets mention one more myth about it and that is, that there are truly 100% hypoallergenic dogs. That is not true, all dogs produce dander or saliva which are triggering the allergies. But it is definitely true, that non-shedding dogs, like Poodles, will have much much lower chance to triger the allergies than for example Labrador Retrievers. So yes, low shedding dogs are better for allergy sufferers, but it is not guaranteed.
4) One dog year is seven human years
Assuming one dog year is seven human years is extreme generalization. There are a large numbers of very different dog breeds, some have lifepan around 8 years, some will have average lifespan around 16 years, which is mostly based on the dogs size. In general larger dogs have shorter lifespan than small dogs. And dogs mature much much quicker than humans, so for example the first dogs year can be equivalent of, for example, humans 14 years.
5) Every dog should have a litter before being spayed
Allowing a female dog to go through heat prior to being spayed does not make her healthier. Today, it is recommended to spay your dog prior to the first heat cycle, which will reduce the likelihood of mammary cancer in adulthood. There are no proven health benefits of letting a female dog having a litter before spaying.
6) Pitbulls are agressive
Pitbulls, but also Rottweilers, all kinds of Mastiffs or Dobermans. These are the dogs that are generally viewed as agressive. Of course, owning such a dog is bigger responsibility for the owner, as they are potentionally much more dangerous than Chihuahua, but Pitbulls are definitely not naturally people agressive. As with all dogs, it is all about the training and socialization.
7) Good dog will not bite
On the other hand, even trained and well socialized dog can bite. You do not see into dogs head. Even if your dog have never bitten anyone before it's impossible to say that a dog would never bite. Dogs bite for many reasons. For example, when they are injured, they might feel more frustrated and fearful and they might act differently than usual. Again dogs might bite for many reasons, such as feeling fearful or frustrated, being defensive, guarding others or intimidation. But of course, well trained and well socialized dog will most likely never bite, but again, it is nothing guaranteed.
8) Teaching old dogs new tricks
This popular saying is partially true, as younger dogs will have more energy into the training and they will probably enjoy it little bit more. But that does not mean that old dogs can not learn new tricks, especially with the right motivation, like favourite treats. Dogs are continually learning and can continue to learn new tricks up until their last days and it is adviced to continuously train your dog something new to keep its mind sharp!
9) When dogs eat grass it means they are sick
It is true, that eating grass can be a sign of some health issue in dog, such as nausea. But, dogs can eat grass from boredom, some dogs will find it fun, some will find it refreshing in hot days and some will just like the taste of it. And as long as the grass is not treated by some pesticides, there is no reason to stop your dog from eating it.
10) Dogs are colorblind
It is true that dogs see the world and colors differently than humans, but many people assume, that dogs see only black, white and shades of grey. That is definitely not true. The color vision of dog can be more likely compared to the color vision of color blind person, which can see variety of colors, but they have problems with some color shades.