Scandinavia and the World

Comments #9872981:

Bio Alarm 7 5, 10:54pm

I don't claim any expertise beyond "have shared a house with chihuahuas and with big dogs" but the claim sounds believable. Chihuahuas have a lot of energy and a lot of noise so they'll investigate ANY noise and sound the alarm.

They normally sound the alarm even when they know they don't need to. But it wouldn't surprise me to learn that a big dog can tell the difference, since they can share subtleties of communication humans don't pick up. "Oh that's the 'roomie coming home late' bark, ignore" vs. "That's the 'new person' bark, better check it out."