I am in need of a few tips for training an older dog. She's a beagle cross, about nine and half years old. I adopted her about a year ago and I know she had minimal socialisation throughout her life. Over the past year we've managed to get her into the the local dog park and she is quite confident now.
The problems we are seeing now is that she appears to fixate on a particular dog and will not leave it alone. She gets right in its face and barks and barks and does not stop for the whole time that she or the other dog is in the park. I've tried grabbing her collar and telling her to sit but once she sees me approaching, she'll dart to the other side of the dog and continue. She doesn't respond to my voice commands either. If I do catch her, I can get her to sit for a minute to calm down and then she's off again to harrass the poor dog. She doesn't do this with most dogs, just a select few. I believe that she is trying to get the dog to run so she can chase (which is her number one favourite activity) but she ends out confusing it until it just stands there. She can interrupt ball games like this, too. Redirecting her to the number of other dogs in the park doesn't work. She just wants *that* one.
I am not really sure how to approach this as she ignores me when she is fixated like that. I would also like her to come when called, which she usually knows how to do at home but at the park she doesn't want to so doesn't come. Does anyone have some advice? I don't really have a lot of dog training experience as she is my first dog that I have been responsible for (grown up with them though).