Some people might argue that the dog was better off tied up. Perhaps. But I don't think so. And no lame comments about it getting hit by a car.....it seems a bit smarter than that.
Heck black dogs are the preferred colour of dogs for the locals to eat. So it's possible someone tied him up so they could come back later to eat him. Who knows. I went with my gut on this one....and it's usually right.