The Growling's got to Stop!

From the dawn of time man has debated why dogs do the things they do. Theories abound. Countless books have been written on the subject. Now I have a dog question.

You'd think I'd understood all Chica’s behavioral quirks, being a dog myself. But not so. She's much sweeter natured than I except at bedtime. That’s when she turns into a momentary monster. When I jump up on the bed with her and my mistress, Chica growls with the ferocity of a mad dog. It’s so primal that it's scary even though I'm bigger. Once I settle in she does stop, thank goodness.

Now I’m no shrink, but my first guess is that she's jealous. But if that were the case why wouldn’t she do the same thing in the daytime when I jump up beside her and my mistress on the sofa? Could it be night blindness? Maybe, but she knows it’s me by my scent. So what is it?

I’m asking the readers of this blog, both human and canine, to help me figure this one out before I lose my cool and bite her.