So far playing the game, the standard zombies/biters have been slow moving, slow to react, with a generally low aggro range and a low ability to climb. However, they are in large quantities.

Playing today, their behavior changed. This was after I finished the tower mission which is early in the story. Now, they all come flocking to me from anywhere within view distance, as if my character is wearing some Zombie Attractor Spray. They move at their fastest speed for biters or maybe a bit faster than their old fastest speed. They are still slower than virals, but with large numbers coming from all directions even when you are quiet/standing still, it is a pain. They also now have gained a much better ability to climb, regularly climbing onto cars, vans, and one-story buildings. Before, that was infrequent and they usually missed, with few making the climb.

The only thing that I have changed was finishing that mission.

I've been playing entirely offline with no mods.

Is this supposed to happen? Or is something weird in my game? It has made it less enjoyable since I can't take time to do anything (even fight a zombie).

Yes, that seems normal. The game gets harder after you complete each story mission. You will more types of biters and more of them as you go through. Part of the main point about the game is pressure, you have to be fast, quick thinking and agile to survive!

Thanks for the reply. I was wondering if my game was somehow bugging. I was expecting that the already-introduced zombies would stay the same, and new types would get introduced to change things up; there are new types but apparently known zombie types also change their behavior.

Yes definitely this happens. I'm not sure if you are at this point yet, but some time early on all of a sudden you'll see all these yellow haz-mat suit wearing types all over the place too.

Others are more subtle, I believe - new variations on the same old biters. These ones look the same as the others, but move much faster. Some seem to also take many more blows to kill, I think these are the same as the faster moving types. When they are just standing around they look just like the basic biters. But you get to recognize their "walk" when you see one moving, where you can tell then if you're looking at the tougher/faster variety. Also at some point some start carrying weapons (those may have been there from the beginning though, I can't remember).

But I think plenty of the same old slower/weaker biters are still around too, they're just not as quick to cause you trouble as the new tougher/quicker variety, so they're maybe less noticeable.

I also experienced that thing where it seemed all of a sudden they had "zombie radar" and were noticing me FAR easier than they had previously. But as I kept playing, I realized there were reasons for this, and that I just had to take even more care to be quiet. Something like a very short fall to the ground may not have alerted them earlier on, but later it seems this same kind of noise would quickly draw nearby biters. Maybe the newer tougher variety has better hearing too? Anyhow, bottom line is as the difficulty ramps up you'll find you need to "pick your spots" where you're going to fight with a little more care, and double down on trying to stay totally quiet when you don't want to be detected.

Thanks, that is great info! I've been on the roofs a lot more, still having fun, just miss sometimes having fun seeing how far I can push a zombie by kicking it repeatedly (or trying to position it by kicking it repeatedly) :)

Wait until you have to retrieve some light bulbs for a quest - you will see how far you can push a zombie!

One of my favorites is kicking them off rooftops. Especially if you find one up on a 3-4 story roof., then you can look down and see how it splattered way down on the ground. Hah, I swear that one never gets old for me ;)

Of course against virals though, that becomes more of an essential survival strategy for me at this point, especially in that area just southeast of the Tower where they always seem to come in packs...

Same. I love just sitting there and kicking 2 or 3 of them off!