One of the most heart-rending experiences I ever had with dogs was about 8 years ago I had a male St. Bernard ("Zorba") and a smaller female terrier mix ("Baby"). Both were adopted through the local shelter. Zorba was left there because his original family was a military family being shipped overseas, and they couldn't take him along. I was on the shelter's list of people to call if a large dog was left because they are harder to adopt out and plus I have always loved St. Bernards too. They told me his name was "Buddy" but he ignored me if I called him that. Normally I try to keep their names (Baby responded to the name I was told she had). Anyway, I decided to give him a new name, and since he was so full of life I called him "Zorba" and his ears perked up as if that had been his name all along.
He and Baby soon became inseparable, and Baby at 30 lbs. was without any doubt the one in charge of Zorba, who was just shy of 180 lbs. They especially loved going for walks around my pond, and we would go several times a day. Well, one day I asked them if they wanted to "go out" and they did their usual dance of joy, and so I let them both out the back door and they bounded out where they would run around and past my Suburban to wait for me to catch up. I saw then disappear behind the truck, and only baby emerged on the other side. I thought that was odd, so I went around to the other side, and Zorba was on the ground convulsing. Within just a couple of minutes he was gone. He was no more than 4 years old and healthy as a horse, or so I had thought. I buried him in my pet cemetery.
Now, Baby was just beside herself for quite a while...she kept looking for her partner in crime almost every waking moment, and always sitting at the door wanting to go out to look for him. But what really tore at my heart was that Baby and Zorba each had their own array of toys each bought for a dog of their size, and Baby gathered every single one of Zorba's huge toys into a pile in the middle of the living room and would sit by the pile waiting for him to come play. She would bark, calling for her pal to come play, but he never came.