My niece has a 6 month old Dashund. She's had her 3 weeks now. When my niece is on the floor wrestling with her 2yr & 4yr daughter, the puppy joins in & tries to bite the 4 yr old. My
Niece tried to prevent it & she was bitten. The puppy never bothers the 2 yr old, but is
Always playing with the 4 yr old. This is the first time she's done this.
Why? Thanks

I THINK FROM MY EXPERIENCE quit often when a dog is playing they get carried away just like kids that are rough housing get carried away.
Maybe the 4 yr old is more aggressive
Maybe the dog is more protective of the 2 yr old and instinctively knows to be more gentle.

I agree. I think all puppies do. There teeth are also sharper. To dome extent grown dogs do to. You can get the "play bite" to the "growl and bite". The growl and bite isn't an aggressive growl. That used to happen when I played with a rag or a "braided nylon stocking".

You play a game called "chase the rag".

This is a bad situation that the adults need to take control of. Keep in mind that dogs see people as other dogs. It sounds to me that the puppy is acting like the kids are other puppies and asserting her rank over them (because that's part of what puppies do in playing... they use it to figure out who's going to give way to whom, and the puppy's teeth are almost guaranteed to make the two kids give way.) This is going to result in the puppy thinking he outranks the kids, and then the family is going to have to work to undo that.

So, while this is natural, the parents really need to put a stop to it now, before it becomes an established problem. And the reason that the dog does it to the older child and not the younger is most likely because the older one is more rambunctious and doing things that the puppy considers as contesting for dominance (keeping hold of something the puppy wants, for example.)

If the dog is that young it is probably teething, not to mention it's a puppy. Im 18 and I'll be playing with my *2 year old* Lab Annie, and she will bite my arm, toes, hands, etc, as play she doesn't want to harm though..

Make sure there are plenty of chew toys, I would deffinately say this is probably not an Aggression issue.

Try more excersize for the puppy

Remember that dogs have to learn how to interact with humans. They don't understand english and they don't automatically understand how we want them to act. Biting is natural in a dog pack, they don't have hands and their mouths are used to explore and play. Obviously this behavior is unacceptable to us, but to a dog it is perfectly normal. You must teach him that this will not be accepted through reward and praise and possibly crating when he bites, it will take a while, but if you are consistent then this behavior will stop. Good luck.

When one puppy bites another in play, but gets too rough, the bitten puppy squeals and backs off. This usually startles the biting puppy and makes him stop. Any time puppy teeth touch human skin with any degree of force, a shrill yelp from the human will serve the same purpose. The 4 year old should be able to learn to yelp (not scream), turn her back for a few seconds, then immediately offer a toy to the puppy. (It's possible that the 2-year old has already been doing this instinctively--her voice is probably more high-pitched-- and the pup has learned to be more careful with her)