OH DEER!! lol
Maybe the deer just wanted to borrow a cup of sugar?

Don't know much about deer do you True.
It is not sugar the deer want but SALT.
Little known internet fact I learned, The herders in Finnland of Raindeer use their urine to draw in and tame the deer. The deer are attracted to the salt in Urine and are tamed very easily.
Only way I can see for a deer to nose a doorbell is if it it coated with salt-----, sort of like the hunters that camp out around a field with a salt lick for the cattle knowing it will also draw the deer.
The Indians found this out and passed it on to the hunter trappers French Canadians.
MY Pep'ere knew this and days before open season would go out alone, find the deer falls and piss on the area tree trunks and brush.
This has to be a scam of some sort, the deer had to be trained to butt the bell with their nose.