I'm new to posting and I think this has probably been covered but:
I went to change My 07 R56 CAF and found it thoroughly destroyed by mice. Finding the inlet behind the battery completely open to the elements, I started looking around to see if my car was missing some kind of grillwork that slips in the hole, but come to find out that's how it's designed, if that's the word to use. UNBELIEVABLE that they'd let them roll down the line that way, especially with the BMW affiliation.

I fixed it to my satisfaction and thought I'd show you how.

If someone has more info that I'm unaware of as to why they do it that way, please let me know.

I'll also see if I can figure out how to get my pics the right way next time.

 

Well actually most vehicles are open like this but also included an inverted J bend, kind of like the opposite of the water trap under a sink so that critters cant crawl in as easily. Thats how my grand cherokees is and thats how the mazda and the nissan I had before it worked. I never did investigate how it was in my former X5, maybe open like this? Im surprised no aftermarket part to cover it

 

It is cheaper that way. Lack of design foresight.

I had a folding machine from England that was made in the 70s-80's. The pulleys were turned with a cloth belt that looked like something you would make at home. The rest of the world was using either rubber belts or chain drives.

I like your fix!

 

I wonder if the same sort of mesh or even a cheap plastic along with a hot glue gun would work.

 

Check your engine bay, I had them chew on wires twice.