I would like the corpses to rot → decay into piles of bones. And some monsters/wildlife to eat carrion/bones.
For now, no fixes as we are in feature freeze. But later, I think all solutions to this problem are not trivial :). So better to look for a good solution.
(I see multiple problems, 1, animals die from acid rain, 2 corpses stick around 3 bones stick around).
I like this solution, but there should be less corpses to begin with… animals would be extinct by now with current death ratio. Most animals should be smart / lucky enough to hide as others already suggested.
I like this solution, but there should be less corpses to begin with… animals would be extinct by now with current death ratio. Most animals should be smart / lucky enough to hide as others already suggested.[/quote]
Four problems! 
(my way of saying, good point).
Bumping… because I am selfishly thinking this one deserves more attention. 
I suggest a threefold approach
Scavengers: Creatures that seek out and consume items. I simply say ‘items’ instead of specifically ‘rotten food’ or ‘meat’ because there’s all sorts of alternative appetites to consider in these dark days, some of these alien beings may have a taste bizzare materials like metals, explosives, leather, cotton (mothman) or wood.
Acid damage is applied to more items, bones in particular should be VERY sensitive to any acid given that you can denature and destroy them using common vinegar. I’ll note here that acid isn’t actually ‘that’ effective at melting flesh or wood (in labs hydroxides are instead usually used to reduce medical and experimental biotic waste to liquid slurry), acid being much more effective against metals (calcium technically being an especially soft and reactive metal.)
Ai is taught to seek shelter appropriately. Likely the most difficult as ties into funny things like the AI being aware of what is classified as ‘shelter’. This may easily change dependent on the 3d rewrite and likely ties into AI overhaul in general. Pathing to a ‘roofed’ area of which trees, houses, caves, wrecks, (or even bushes assuming the creature is small enough) is the most apparent option for bad weather.
Why not leave the whole process up to natural selection?
The effect of acid rain changes depending on the amount of time spent in the game.
Early on animals will be killed very quickly by acid rain
After a season or two they will be killed more slowly
After a year or so they should be completely immune.
It also works well as a way of gradually having the difficulty increase.