funny behaviour

holly is bo's mum.
at first when bo was a pup and i opened the back door she would run out and wait for holly, when holly went out bo would play with her.
but lately its gettnig a bit bad. bo is really being aggressive with holly, and of course holly being alpha female is really fighting back
ive tried puting holly out first then allowing bo to follow after a few mins but she seeks her out and attacks

hmmm tough one. Maybe let them out one at a time for awhile. Sorry its a tough one.

it is, i dont know why bo is doing it. they are so good together on walks and in the house, but its just when they get out the back

My best advice would be to apply to Creature Teacher Emma . . .

It sounds to me as though you may have a barrier issue. Some dogs when going out or coming in something will become very aggressive. I would suggest keeping Bo on leash when you first let Holly out, maybe walk outside with him on the leash for a bit and then let him off. By that time he may have forgotten to go after Holly because he is intriqued with being outside. What happens when people knock on your door? Do your dogs respond by running to the door and barking? This is another situation in which barrier issues will present themselves.
I hope someone can give you some more ideas on what it is and how to train Bo out of it. How old is Bo? Is he hitting "puberty" now? That is when most barrier issues start.

The leash sounds like it might be a good try, Adrienne. I've got to ask though, "barrier issues" or "Terrier issues"

hi, bo is holly's child. she is a girly, and she's 2.
she doesnt do it with darcy and people coming to the door is usually just a short bark from their beds. i tried taking them out together on leads, seperately and l;etting holly run while bo was on a lead, all resulting in the same thing, the second they were together again bo started. bo doesnt do a thing in the house to holly and on walks and at feed time