Animals and Gargoyles (and stuff) on Churches: The Mycology of Faith ?

I am not sure we understand the purpose of the gargoyles that so famously adorne the wonderful churches of Europe. One imagines that they have some (spiritually) protective function but that may just be a collective intuitive assumption.
St. Vitus in Prague certainly has its gargoyles:

Even more of a mystery to me is the presence of all the other animals of God’s creation :

That this can extend from zoology to botany or even mycology is also of interest. I was intrigued to find a clump of mushrooms high in the corner of a door !