When our collie, Buckaroo, was four months old, he began barking at his reflection in our glass patio door every evening, doing his best to alert us to this unknown, bold little pup outside. Of course, the reflected dog didn’t back away, so Buck lunged at him and scratched the door jamb—actions that did get our attention. We would pull him away, laughing, and tell him he was wrong—a dog wasn’t on our deck.
Buck studied our faces with a perplexed expression. Anyone could see the dog was still there. Why didn’t we chase it away? Sometimes, we opened the door to show him he was mistaken. Of course, as soon as we closed it, the strange dog reappeared. The reflected dog also had the irritating habit of mirroring all of Buck’s actions. In other situations with new dogs, Buck would have made a series of welcoming gestures, perhaps wagging his tail, rolling his eyes and making deep play bows. We never saw him make a single attempt to befriend this ‘Now I’m here; now I’m not’ canine. He tried only to make him go away.
At some point, when he was a few months older, Buck ceased being interested in his reflection. Undoubtedly, he still saw the dog, but finally accepted that it wasn’t going to leave. Apparently, he decided that it wasn’t going to try to come into the house either, so he didn’t need to bark and scratch. Perhaps Buck had concluded it was simply better to ignore this apparition. That’s our best guess because, of course, we don’t actually know what he thought about his mirror-twin—we can make only hunches based on his behavior.