Oye! I have actually seen people do this to cars at shows when they see open stacks. The Devil never sleeps. Serious consideration should be given to a method of vermin elimination to ensure that they can never reproduce and spread their curriculum with personal seed. I think instant vaporization should be considered as appropriate and in order?
You have to cover the tops of the stacks for your own good to protect from that kind of a malignancy.
Back in the day I saw the Formula 1 cars with tennis balls in the stacks when parked in the pits.
Even the GT40's had a cookie tray mounted over the top of the Webers. You can decide what you think the reason was but I suggest that there was more then just one reason.
Both of these are stack drop ins and are stainless steel so if you don't like them you can use to strain the pulp out of your morning orange juice. That's what I told "wifey" what they were for anyway.