Harder Wildlife is an alteration to the Minecraft world at large. Animals and trees automatically repopulate and die off leaving behind rotting wood, seasons change, snow falls, accumulates, and melts. Crop growth is slowed and takes into account biome attributes. It takes more wheat (seeds, etc) to make animals go into "love mode," but they drop more meat and leather so it is no longer painfully scarce. Killing a sheep gives more wool than sheering, and finally goats and Monitor Lizards are added to the mesa biomes, to provide additional access to leather, wool, and food for biomes where it is otherwise scarce.
Part of the Reasonable Realism collection.