I have an 8 year old Jack Russel.... I used to have a black Labrador and they were the best of friends, she sadly passed away this year and since then my JR has become very aggressive towards other dogs. In the parks she is fine approaching other dogs and if other dogs run to her she is fine, but as soon as I get close to the other dogs she starts growling, snapping, going in for the kill. I also have dogs from time to time staying at my home, she used to be absolutely fine and chilled and didn’t care, now she is so aggressive if any of the dogs come near her, or pay her any attention, especially if I am in the room, she will jump on my lap and snarl, growl and snap - she never actually makes contact with the other dogs so there are no injuries but she is definitely trying to intimidate them?! Does anyone know the reason? Is she just getting old and grumpy? Is she over protective? Is it something to do with my other dog passing? HELP?