possessive/aggressive behavior

Question
Hi,
I adopted a 2 year old Great Dane about 6 months ago.  She bonded very strongly to me, very quickly.  She has displayed some aggressive behaviors since I got her:  ballistic barking at the door, and lunging at some dogs when she has a barrier in between (in the car, by a fence, etc)  She will bark aggressively at servers in the drive thru windows as well.She escalates when I pull her collar. She has just begun to occasionally chase people who are leaving the house-including my husband and become much more protective/aggressive with dogs at the dog park-especially around the water bowl.  I make her lay down when any of this happens, but am worried that she is escalating.  BTW I have another dog she gets along great with. We have been through obedience and I have good control of her in the house, but am worried about her behavior outside of it.  Any suggestions?

Answer
I would say she needs a lot more training. I'd find someone who works with reactive/aggression problems and stick with it. For a lot of dogs, a single session of obedience classes doesn't even start to meet their needs. While I was training, I would carefully control her environment, gradually exposing her to new stuff, at levels where she can handle it. In addition to getting professional help, I'd suggest a couple of books which should be helpful to you - "Click to Calm" by Emma Parsons and "Control Unleashed" by Leslie McDevitt. And a dog with this sort of issues should not be in an off-lead dog park. Sandy Case MEd CPDT www.positivelycanine.com