Picture it (I'm sure you can)- You are a dog. You have your house, your people, your bed, your toys, your bones. When you want something, there it is. Whoever comes to your house wants to cuddle you. If your humans want to play, they play with you. You're on top of the world!
Then, something changes. Suddenly, there is another you. They chew your toys, sleep on your couch, and get treats from the humans. Your humans. Only they aren't just yours anymore, you have to share them. You have to share everything, and it's just not fair!
I don't like to share. My mom calls it 'jealousy.' I call it logic. I used to have 100% of everything I wanted. Now I have 50% at best. Sometimes, I have even less.
Now, some less intelligent dogs don't mind this. Some love it. But those of us with half a brain realize that this subtle takeover must be stopped. Of course, we can't do anything too drastic- we have to ensure that the humans still adore us in the end.
My general game plan is as follows:
Hoard the best toys and bones in my man cave.
Ensure that any attention to the invader is blocked and redirected to me.
Make it abundantly clear that the invader is in hostile territory. Again, subtlety is key. Practice your stink eye in the mirror, and perfect the "drive-by"- a slow walk, freeze (insert stink eye) and move on before the humans notice.
Hopefully your invader is clever enough to put the pieces together. Unfortunately, we can't all be that lucky.
Of course, if your humans notice that you are resisting the new addition, the gig is up. They'll use their training magic to convince you that you do, in fact, enjoy the presence of the other dog and then you're doomed. Tomorrow I'll share with you how my Mom convinced me that sharing is caring. I don't always buy it, but she keeps working with me and sometimes I forget that these other dogs are invaders at all. Weird, huh?