[PatrickHenry]

Do dogs see in black and white?

I had a dog who could identify Federal Express trucks, UPS trucks, and of course, mail trucks. Whenever one of them would round the corner, she'd go nuts, expecting that they'd pull into the driveway, as they sometimes did. No other trucks would set her off. I assumed it was their colors that she recognized -- at least UPS, which is somewhat distinctive.

[RightWhale]

Sound--delivery trucks use odd little motors

Odor--delivery trucks burn unusual fuel

Mind reading--dogs sense intent to deliver

[Myrddin]

I can hear the FedEx, UPS and U.S. mail trucks coming a block away. The sounds are distinctive enough that I don't enough need to look out the window to discern which one it is.

[blam]

My dogs go crazy when the meter readers arrive. I finally figured out why...they had used mace on my dogs in the past. They each walk up to the meter with a spray can in their hand.