OK, I finally saw what I have been hearing in my crawl space... a rat. I haven't seen any others but may be another. It has pulled off the flex duct on my return and is running around inside the duct! Any suggestions? I placed a humane trap in the crawl space with peanut butter and bread... nothing! Any suggestions for a food?

Keep the trap there. Unless he has access in and out of that duct for food then he will eventually go for it.

Rats are neophobic - afraid of new things. Put an empty trap down for a few days, then add food near it. Then bait the trap. When you place it, put it perpendicular to the wall so that it snaps toward the wall.

ok, i finally saw what i have been hearing in my crawl space...a rat. i havent seen any others but may be another. it has pulled off the flex duct on my return and is running around inside the duct!! any suggestions? i placed a humane trap in the crawl space with peanut butter and bread...nothing!! any suggestions for a food?
Mix some cement & flour together, put a dish of water close by. They won't be around long after that.