while normal difficulties swarm the area with animals of all kinds, insane has almost no animals at all and the few that do spawn are very soon caught and eaten by the Zombies on higher speeds (mainly nightmare)
it might be necessary to increase animal spawns on high speed settings to somewhat counter act the Zombie hunting
with that i would recommend doubling the spawn-rates so that they replenish faster rather than increasing amounts that would flood the area for a short time
