Either someone else got really close or she was such a slut the dogs wore her tail off!
+1 also if born in a big litter 7 or more the weakest pup gets hammered on , the tail is the first target. After they all join in the fracas the tail can be torn off. I've seen this several times when we dug up dens in the past. I saw one female coyote shot before giving birth that had 13 pups in her all lined up perfectly in the canal, my vet dissected her and was astounded. He wants some bodies this winter to see if any coyotes are heartworm positive.It could have been born Natural Bobtail