Some More Observations: Today I spent a fruitful hour lurking on the roof of my local Brookshire's, mapping and studying the physical appearance of the Shopping Carts (as they are called in the common idiom.) In this particular location I noticed a great deal of reddish tinge on the bodies of these sleek creatures. My first assumption was that their chromium hides were showing signs of rust, and therefore neglect or poor feeding habits.
I couldn't, as it turns out, have been more wrong. Upon closer inspection it turns out that this 'rust' was not a physical surface feature, but was a naturally occuring colour trait of the creature's hide itself.
My exhaustive studies indicate that it is a basic trait of these creatures to have a small ability to alter the outer colour of their hides -- in this case, to the appearance of rust, much as some lizards can alter their skin colour to better blend in with their surroundings. This serves as protection, in that the 'rusty' Shopping Carts are better able to blend against rusty cars (which naturally appear in their habitat, especially in Louiaiana) as well as making themselves appear much older and perhaps damaged, so as to make themselves less likely to be chosen for shopping use. This, of course, leaves them free to roam the open herds of females to choose a potential mate.
What wiley and beautiful creatures these Carts are!