I trust my sleeping dog (yellow lab) with my life - honestly. If he wakes up in the middle of the night to a noise he doesn't appreciate, he will let me know with a low growl and his hair on end. I appreciate the growl at night versus a bark as it gives me the element of surprise if someone is in the house. He will not bark if the kids get home late but if one of their friends is first through the door or someone new is in the house, he lets me know.
A few nights ago, he sat up promptly on the end of the bed and let a growl loose. It was 2:30 AM, or thereabouts. I vaugley remember hearing a bump in my sleep and before I had barely woken up but he was already on alert. I grabbed the shotgun, let him out the door, and followed him to investigate.
Finally, after about 5 minutes of searching, I figured out what he'd heard. A string of X-mas lights had slid off a a railing and tapped the floor. As soon as I saw it I knew it's what I'd heard in my sleep but it wasn't a noise he's ever heard.
2 years ago he let me know someone was outside in the cul-de-sac that shouldn't be. We live in a nice neighborhood so for him to be upset with something outside is RARE. I looked outside and I found my neighbors car being broken into. A 911 call and 10 minutes later 4 punks were lined up on the curb in handcuffs. I have no idea how he knew, but he did.
I sleep well knowing that if anyone were to sneak up stairs I'd know before they ever opened the door, and that's plenty of time to arm myself.
--Duck911