Killer Bunnies no longer spawn naturally within Minecraft.

To reproduce this bug load up any minecraft world and observe that no Killer Bunnies spawn.

There was a 1/2500 chance to have a Killer Bunny spawn in 14w33c which can be seen in this code provided by redstonehelper:

r(paramaqo.s.nextInt(6));
if ((paramaqo.s.nextInt(2500) == 0) && (paramaqo.aa() != vs.a)) {
  r(99);
  a("entity.KillerBunny.name");
}

However, in 14w34a and all subsequent versions the code is very different. In the 14w34a changelog this change was not mentioned so it may be unintentional.

This is a difficult bug to test without referencing the game code directly. Still, I did try to test this myself by spawning in rabbits via command block for 3 hours with a detection system for Killer Bunnies. In that time I spawned in ~30000 rabbits but not one was a Killer Bunny. It is worth noting that this method of testing may be flawed due to the spawning not being totally natural but the lack of Killer Bunny sightings online and via my own experience confirms that Killer Bunnies no longer spawn naturally.

You will find more information about this on the Mojira subbreddit as I have been discussing this with several of the mods there about if this is intended behavior or not.

Mojira Subreddit discussion: http://www.reddit.com/r/Mojira/comments/2znn4z/a_potential_bug_that_im_unsure_how_to_report/