A PARTICULAR TYPE OF BARKING

Question
LABMAN,

ONE OF MY DOGS, SOPHIE, A TERRIER MIX FOUND AS A PUPPY ON THE STREETS, HAS A HABIT OF STANDING IN THE BACKYARD AT NIGHT AND EMITTING A SINGLE BARK ABOUT EVERY 30 SECONDS. SHE WILL STOP WHEN TOLD BUT OUR JACK RUSSELLS ARE TAKING UP THE HABIT AND THEY ARE NOT SO EASILY DISSUADED. THIS ONLY HAPPENS OCCASIONALLY AND STARTED DURING A CAMPING TRIP WHEN MY GERMAN SHEPHERD(12 YRS) WANDERED OFF.  AFTER 6 HOURS OF LOOKING, WHEN WE TRIED TO GO BACK INTO THE CABIN, SOPHIE REFUSED AND SAT AT THE BOTTOM OF THE STAIRS AND GAVE OUT A SINGLE BARK EVERY 30 SECONDS.  AFTER 15 MINUTES WE COULD HEAR THE OLD BOY HOWLING IN THE DISTANCE AND EVENTUALLY HE MADE IT BACK TO CAMP. SHE SUCCEEDED WHERE WE HAD FAILED.  NOW SHE JUST DOES IT EVERY SO OFTEN AND WE WONDERED IF MAYBE SHE COULD HEAR OTHER DOGS IN THE DISTANCE?
ABOUT 6 MONTHS AGO MY SHEPHERD PASSED AWAY, SO SHE IS NOT 'BARKING' HIM HOME.  WHAT IS SHE DOING?

Answer
I think it is possible she is missing him and is trying to once again bring him back.  My usual cure for barking is to bring the dog in.  You can't have the 3 of them out there barking.  

You might talking to her and explaining he is gone.  Try to picture whatever you did with him in your mind while talking to her.  My ration side says that will be a waste of time.  Still, dogs seem to understand things sometimes in ways we don't understand.