So my pem Einstein has had a recent obsession with barking at the dogs on the other side of the backyard fence. This started about a month ago, and he is about a year old. He has a very friendly personality and has no problem with other dogs, cats(and even our guinea pig). But as soon as we let him out into the backyard to use the potty he runs to the back fence and starts barking, growling, and scratching at the back fence, his tail wagging the whole time and his ears upright! Other times I will try to play fetch with him outside but as soon as he nears the back of the yard he starts antagonizing the other dogs. As soon as I call him he leaves them alone, but why is he so suddenly obsessed with bothering the neighbor's dogs?