The normal animals of the cataclysm (non-mutant ones) are a little neglected compared to the rest of the game (both in terms of mechanics and lore) being largely forgotten by the community as a whole. Despite that the normal animals are an important part of the game and of the world at large. So, I came up with some ideas for how they could be expended upon in the game as well as extra lore and explanation as to how animals would survive in the cataclysm.
For gameplay I came up with a few things that animals should do or what role they would play in the world at large. As well as my rational/potential lore behind it.
Many of the scavengers and omnivores before the cataclysm would most likely scavenge human garbage and food as part of their diet. So, they should continue this behavior in game by opportunistically eating the food items that the player drops or leaves lying around. So, you would have to properly store your food or have it be eaten by animals. This could also be used to set lure some animals as part of hunting.
Herbivores should be able to eat and be attracted to any crops the player has planted as they do in real live, thus incentivising the player to plant in an out of the way location where animals won’t find it or can’t get to or build obstacles to prevent animals from getting to there crops. This would serve to expand the amount of pests in the game to make farming more challenging and complex as it is in real live.
Then there is the matter of all the corpses laying around the wasteland. There would be many scavengers and omnivores that pre-cataclysm relied partially on human food and garbage to survive looking for new food sources now that those are now longer available on account of the humans being (un)dead, their food situation also would not be helped by the fact that most large corpses have only a few hour window where they can be eaten before they aren’t corpses anymore. This combined with the fact that many scavengers are highly opportunistic and adaptable in what they eat would mean that any corpses including zombie ones that are lying around should be sniffed out and devoured in a couple of days to a week leaving nothing but bones (presuming they are in a forest, swamp, field or an out of the way location that is not infested with the undead). All this could be put into the game by having corpses turn to bones as they do now only way quicker to simulate them getting eaten by scavengers. As well as seeing scavengers spawning/being attracted to corpses and eating them damaging them in the process and eventually reducing them to bones.
It would be combined with the eating of food items a nice organic way to dispose of corpses and rotten food/butchery refuse when vermin are implemented proper by just dumping it into a field or forest and letting the scavengers take care of it. It would also mean that any corpse that could revive wouldn’t necessary revive if the scavengers got to it first. That might also go for any non-pulped zombie corpses laying about in field and forests since there are animals in the game that could eat enough of a corpse that it should not be able to revive anymore.
(Can’t wait to kill a horde of zombies only to return two days later to see a horde of animals devouring the corpses and a week later nothing but bones remain).
Then there is the matter that the amount of normal animals the player sees later on in the game is supposed to be less and less as they see more and more zombified/mutant animals. I have tried to look for a lore reason for this and although I found that this part of the game doesn’t have that much lore behind it (or I couldn’t find it but my point still stands) since this part of the lore isn’t discussed very often. Usually what explanation I did find was a vague explanation about zombified animals, zombies and mutants outcompeting all the large normal animals and them being functionally extinct in a few years. However I find this explanation both from a gameplay and a realistic perspective kind of dumb because normal large animals are supposed to be in the game even after a very long time (as a non-poisonous meat source) although in reduced number but at a stable rate thus suggesting that they did find ways to survive in the post cataclysm world so there should be a explanation for why they continue to exist in the world and aren’t wiped out by the undead or mutants. The reasons I can come up with are that:
Zombies and zombified animals aren’t that dangerous to wildlife which would explain why all the deer, wolf, bears and moose aren’t all zombified
Zombies are so dangerous because they attack on sight and charge anything that moves relentlessly. But because of this they do not sneak they, do not try to hide, most zombies seem to have worse senses then when they were alive unless they have specific mutations. They are relentless killing machines but anything with a function brain can detect them long before the zombie can detect it.
A individual zombie or even group (unless a zombie master is present) does not use tactics or have much intelligence to speak of, they cannot learn anything, and seem to be slower and clumsier than when they were alive unless they have specific mutations. If it came down to it a living animal could simply run away (and most animals naturally do) and would stand a very high chance of escaping most zombie’s or zombified animals.
There would be zombies such as zombie cougars, wolf, dogs and things like feral predators that would have the problems mention above to a lesser extent and might be successful in killing some prey but most of those would still face the problem that they are try to kill anything on sight that isn’t blob. The reason this doesn’t happen in nature is because this is a terrible survival strategy. Because eventually they would run into an animal that is willing to fight them and is stronger than them. Things like a pack of wolfs, dogs or a bear would most likely win against a zombified dog, cougar or even a feral predator and the varieties of zombie such as brutes, shockers, hulks and skeletal juggernauts that could beat these animals have the same problems as described above. And that isn’t even mentioning all the mutants, giant bugs extra dimensional horrors running around.
If a zombified creature dies outside of an area with a lot of other undead than there would be a chance that it wouldn’t be able to revive since there is nothing to protect it from scavengers seeking to eat it. Or if it is killed by a wolf/dog pack or bear and they decide the body is a nice dinner than they, (wolves can eat about 10 kilos of meat in one go so a pack of five wolves eating a zombie corpse would likely be able to damage it enough to prevent revival not to mention the other scavengers that it would surly attract)
Many of extra the dimensional horrors, giant bugs and other mutants running around would be more of a problem however animals would realistically adapt to a extent by quickly learning what is dangerous and avoid said danger, adopting their behavior to these new creatures as any normal animal that fails to do so would die as a result. The most likely change in behavior that we would see is that animals become a lot more skittish as a result of the many strange and dangerous things that are now part of the ecosystem this would explain why the player encounters less and less normal animals in later in the game as wildlife gets more skittish and is seen less often but encounters more zombified animals as they do increase in numbers up to a point and do not avoid humans.
There is also no guaranty that mutants or nether creatures that we see would become invasive and royally screw over all of the existing species. What seems more likely by the implied stabilization of the animal/monster populations in the late game means that some kind of new ecosystem has been formed (anywhere that the triffids/mycus doesn’t take over) in which the new species have found their own niche and a new ecological balance has been formed. This would also explain why the be ecosystem didn’t collapse as you would expect form a mass extinction of most normal creatures and after that the mutant that prayed on them and the plants which wouldn’t be fun form a gameplay perspective.
Source wolfs: https://animals.mom.me/much-wolves-eat-average-3840.html