This music. Them feels of isolation and walking around at night with very little food. God-tier ost. Why haven't you played Tokyo Jungle?
Survival is like that but there is a story mode. You do have to collect a few marked items between levels in survival though. It's actually quite good the story...particularly on the last few levels.
Survival is the best mode though. Just feels good trying to survive and going to all the different areas that have food (and you get more intimidating enemies as the years go on so you're always on edge).
If I remember correctly you just have to complete objectives in survival with a specific animal to unlock another. I didn't unlock them all though. Just got a bit consuming and difficult with some of the weaker animals.
Yeah a bit of a pain because it you die, it takes you back to the room before and you have to fight those sub bosses. Felt so good though beating the game but even more so going past 100 years and getting that 'king of the jungle' trophy (without that robot dog thing).
>enemies past 100 years
Yeah you would have to try and use medicine. There's usually lots to store. Or use sewers and make sure to open up the entrance where you start off near. Would be good if you could set a few custom options like no toxicity.