I have a two-year-old blue Great Dane. He was neutered at about 7 months old. He's a very sweet dog, great with our five-year-old son, and good with our other dog, a 4-year-old Shepherd mix (also male). He does play rough with our other dog and he's still very much a puppy--gets hyper and very excited when we get visitors at the house.
We really focused on socializing him as a puppy and have walked him in many crowded places, where he draws constant attention (and petting). He was a little wary of men as a puppy and isn't 100% great with other dogs. He does go to doggy day care and has never had a problem, but he fence fights with a pitbull next door and has lunged at dogs on the sidewalk while leashed and walking on two occasions. But generally he's a good boy. He's always been excellent with kids, very aware of his size.
We don't have a lot of visitors over to our house and because of his size (150 lbs.) and energy level, he often gets put away or kept in another room when we have people visit, depending upon their comfort level with big dogs.
My partner's stepmother arrived today for a visit. When they got home from the airport, she decided to take a nap. At the time the dogs were outside. We let the dogs into our den (which is gated off) while the stepmom napped. After a couple of hours she woke up. My partner and I were in the office when she came downstairs. The gate to the den is right next to the office (she had to walk past the gate to get to us). I don't recall if we said much to her when she came downstairs, which is only a short hallway from the office. Anyway, she was walking down the hallway to the office and the dogs realized she was here (likely for the first time), and they both ran to the gate and jumped up on it, freaking out with excitement. No barking, no growling...both of them wagging their tails and going nuts trying to get to her. From my vantage point in the office, all I saw was that she raised her arm (not sure if she was going to try and pet them or what), but then I heard her tell the Dane that "that's not nice" and she informed us that he'd bitten her. Indeed, she had a couple puncture marks and started to bleed.
I am completely shocked. I don't feel like he was being aggressive, necessarily, because his body language conveyed more high excitement. I do wonder if part of the problem is that she suddenly "appeared" in the house...there was no coming in through the front door, just all of a sudden here this stranger is (she visits about once a year and has met him twice before) walking down the hallway. We didn't introduce them or manage the greeting at all. Usually when we have visitors we try to have them greet the dogs one at a time, because they are just too overwhelming when they're together. The stepmother is blowing it off, saying it's not a big deal, that "he was just trying to hold onto her", though she also said he was "just trying to protect [us]".
It's not okay with me. I'm just floored, as he has never shown any signs of biting before this. He wasn't even a mouthy puppy. He has never been mouthy, even playfully. I'm not sure how to interpret this, or how to feel. Not sure if I should be worried about him, or if he was acting within his instincts, not motivated by aggression. After the bite, my partner stood in front of the gate and told him to sit/calm down, and at that point he stuck his head over the gate and the stepmom was able to pet him. No growling, tail wagging.
What do you guys think? Do I have a problem on my hands? My (elderly) parents are visiting next week and I'm pretty sure I don't want him around them at all. In the past we've limited their exposure to him just because he's big and rambunctious and they're not all that comfortable with dogs...but I don't want to see this dog as something bad if he's really not.
I'm just super confused.