This was a question someone asked Mr. Google, who subsequently directed them to this Scottish Terrier site. Alas, Mr. Google was uncharacteristically unhelpful in this particular case as we don’t have the answer. But our readers are a knowledgeable bunch so maybe one of them knows. And of course, it’s a good question for Inauguration Day.
P.S. Apparently Barney and Miss Beazley left Washington early to stay with relatives in Texas, which is why there were no shots of them getting on to the helicopter.
Update: The more I think about this the more I am convinced Barney was neutered as his male parts were never exposed in any of those many videos and photos.