Guarding is where a dog will possessively guard either food or toys, to the point where it is dangerous for anybody to approach them. You can see how this would be a desired behaviour for an animal’s survival in the wild, but also that it is less wanted with a domesticated animal.
Dog guarding is a common issue encountered by many pet owners. It is, however, important to remember that this isn’t necessarily your fault; guarding is both a learned and instinctual behaviour.
The easiest way of avoiding your dog learning this behaviour is through early training. You need to show them that losing the guarded item isn’t the worst thing in the world, and that it often leads to something better. If it is an existing problem with an adult dog, you do the same thing, only much more cautiously. Start off with something they don’t care that much about, and try to entice them away with treats. Move progressively closer until you can take the toy / food away from them before you give them the treat.
