Wow, that's interesting. I think they are drawn to animals (and children), or sometimes they just like to get in the picture and since you take a lot of pics of the dogs that's where they seem to show up more often than not... ? Hard to say. Try taking some snaps of the house, in the rooms, etc. too.
Maybe the orbs are trying to comfort Sookie? She looks kind of sad in these lastest pis - with good reason. ='(
Kell