My dog Sable, a rather largely built Shetland Sheepdog, can tell if someone is in the near vicinity of our house no matter what. He stays at moms place cuz I cant have him at my house. you could be sitting there watching TV or doing something else and if he gets up and goes to a window, and know there is someone around. he'll bark and raise holy hell till he sees the person. it's kind of handy becuase the well-pedestrian-travelled railroad tracks are right next to the house.
And a few days ago, I noticed him limping. mom tells me that the chihuauha next door ran over to him while he was tied in our yard and took a snap on him. So i took him to the vet. He says it messed up his shoulder tendon or something, but he gives him some painkillers and does some bloodwork. Come to find out it affected him badly becuase he has Lyme disease (that disease from 2 towns over)and his white blood cell count was down because of it or something. i think me and the neighbor, who is about 3 months new, are going to have a little talk about the vet bill.