Whoaaaa! Freaky! My psycho dog Kobie does this too! Her "job" is to watch for glints of light and shadows, and to pounce on them when she sees them moving on the ground. She does this with birds, butterflies, and dragonflies that fly over the backyard (she never looks up to see the actual critter--only its shadow!), as well as with glints off of wristwatches, glass, mirrors, or anything shiny. She can occupy herself for hours doing this, if we'd let her. We don't, though, because we already think she's got a screw loose...why let her drive herself completely insane?

BTW, she's an ACD/Husky mix (we think) with a huge prey drive and a serious compulsion to guard the house. But she's a sweetie. You need to post a picture of your roommate's dog ASAP!

And finally, welcome to PetTalk! I grew up in beautiful San Diego (Poway, actually) and miss it sooooo much! Jackie with the Schnauzers (she'll probably be along soon) lives there too.