All dogs in the household must be nice to one another.

Whenever my sister describes the antics of my two nephews, I often exclaim, "Oh, my God—my dogs act exactly the same way!" Luckily, she doesn't get offended. The similarities between doggie sibling rivalries and young boy sibling rivalries can really be striking. I guess it stands to reason because we all, humans and dogs alike, want the same things—attention, praise, affection, tasty food … and we all get a little out of sorts when we don't get those things or when someone else is getting more than their fair share.

I used to think that it was OK to let dogs "sort things out" among themselves with regard to their hierarchy. Perhaps it's OK when the dogs are pretty mellow anyway or there isn't a very strong rivalry among them, but things can get out of hand with high-strung, competitive dogs who never quite got the hang of bite inhibition. I remember receiving a message and some photos from an acquaintance who said that her two dogs had had a "playing accident." It turned out that one of her dogs had attacked the other, leaving a long deep gash, and she still thought that it hadn't really been intentional and that they were going to work out their differences eventually. I told her they might die trying. Did she want that? And if not, it might be wise to engage a dog trainer or behaviorist right away.

When I was writing a column for PETA's in-house newspaper, I received this question:

[My female dog] stalks and hunts [my male dog] in the back yard and has for years, but it was done in a more 'playful' manner, though Rufus (not his real name) never appreciated it. Greta (not her real name) also has always demanded everyone's attention over Rufus', and if left alone in the house, she will not allow him to have any toys or chew bones. … Just recently, Greta has been attacking Rufus and will not allow him on the back porch at all.

I answered her like this:

I think that what’s happening with Greta and Rufus is a very natural progression. Pushy dogs tend to keep on pushing until they attain leadership, and Greta is doing just that, but she’s gone too far. You need to take matters into your own hands and not allow her to treat Rufus this way. If you see her threatening him when he wants to go onto the porch or play with a toy, step in, looking as tall and imposing as you can, and [make a sound that will catch her attention] while staring her down to register your strong disapproval ("No" just doesn’t cut it with dogs―speak to them in their own language). Make her back down. Make her realize that you are the one who decides who gets to play with toys and who gets to go on the porch, not she. You'll have to do this consistently, but she'll get the message, and she won’t be offended. I'm sure she’s a quick study, as most dogs are. You will find that Rufus becomes a much happier camper. I actually saw this same scenario played out by my own dogs, Sunny and Dexter. Sunny used to enjoy stalking Dexter and knocking him down. Then one day at the beach, a woman who was jogging past me and saw Sunny doing this shouted, "Don't let her do that! Stop it!" and a lightbulb went off in my head. "Hey! I don't HAVE TO let her do that to him!" And ever since then, I've stopped her from doing it, and Dexter is much more carefree now. So is Sunny, truth be told. She no longer has to keep Dexter in line because someone else (yours truly) is doing it for her, although not by knocking him down.

I do believe that we should intervene in any doggie exchange that is likely to cause even minor injury or anxiety to one of the parties. Even when it seems funny or cute to us, such as when a small dog wants to terrorize a larger dog. I've had to deal with this issue with my foster Chihuahuas—they had a bit of a Napoleon complex, and my big dogs were starting to feel pretty uncomfortable. So I stepped in and made it clear that the little girls were out of line.

Cesar Millan of the Dog Whisperer TV show tells people that the hierarchy in a household with dogs should consist of only two levels: the leaders (the humans) and the followers (the dogs). That means that all dogs in the household are equal—even visiting dogs and foster dogs. Although I don't agree with him on everything, I do agree with him on this point for the most part. I think that it's an excellent way to keep the peace. No one should be allowed to get away with being pushy or snappy. All dogs in the household must be nice to or at least tolerant and respectful of one another. And if one of the dogs has a serious aggression problem, then it's time to call in the professionals.