I have gleaned the following from the internet – and other sources:
Mice can jump an average of 12 inches vertically and four (4) FEET horizontally!
Exceptional mice can jump 18 inches vertically.
They are known to gnaw on wood spars and rib stitching. I have seen some really messy results...potentially life threating when the aircraft is aloft.
It takes an exceptionally SMOOTH surface to prevent them climbing vertically.
Their urine is not nice -can lead to corrosion, as well as infection.
Their scat (droppings) can be dangerous. Collected in a fuselage, scat can be a gathering place for moisture -hence corrosion. It also is dangerous as a source of infection.
They carry many dangerous diseases…including the formidable Hantavirus.
They can pass through holes as small as 1/4 inches. They can flatten their bodies to enter incredibly small spaces. Even small bats (We should call them flying mice?) can get into incredibly small holes.
If you want to keep mice out of your aircraft...I think the following might work. It might prove satisfactory to use a very smooth galvanized metal ring (collar) around the main gear and the third wheel should have a ring around it. If you have a taildragger the ring on the tail wheel might be quite large in diameter in order to clear the lower rear fuselage and any tail brace wires and the rudder. The height of the metal rings should be (safely) 19 inches although 13 to 14 inches might be enough for the average mouse...but not enough for competitors on Mouse Olympic teams.
Properly designed rings should easily encircle the wheels and then clip together to form a complete circle. Where they clip together the joint should be very smooth and run vertically.
Keep the aircraft at least four (4) feet away from walls, boxes, other aircraft etc. -to prevent mice from jumping from one place to another.
Consider putting baited and simple mouse traps inside the rings...as a secondary precaution.
It is possibly very unlikely that chemicals or electronic mice "discouragers" will actually work. Mice can get used to electronic outputs -and often just walk on by chemical "discouragers".
Chemically poisoned mice can die ANYWHERE -even inside your aeroplane, your toolbox, a carton, or on the hangar floor. Handle with care. Wash your hands afterwards.
I know of some insulated hangars where the mice live in the wall insulation -also the ceiling insulation. In the ceiling they mimic bombers and sprayers…
Climbing walls, they can be very adept -acrobatic even- although I have not yet observed any vertical rolls. Lomcovaks and rolls on descent but no climbing vertical rolls. Not yet! (Perhaps with time...?)
If the aircraft is parked outside and there is a heavy snowfall, all bets are off! The rings will be covered/filled with snow!
Rings used outside should perhaps be staked down when installed because in heavy winds they might bounce around and cause damage. Needless to say the aircraft should be well staked lest it bounce against the rings. (The main target of what I write here is the hangared aircraft.)
Try to smooth off the upper edges of the rings –possibly by using rubber channeling in order to prevent injury to visitors…with resulting litigation.
Perhaps others will be willing to share information/suggestions on this topic…
A simpler and better solution would be pleasing indeed.
The photos here show devices made up by Dan Hieronimous for his
Marquart MA-5 Charger homebuilt biplane. They encircle the gear and clip together to form a mouse barrier.