@seburoc-26 I see this as game like setting. Author also mentioned at the beginning that there more monsters during spring and as time progress these number drops, and during fall remaining one hibernate (most of them). Some couple of chapters before, it was mentioned that they get closer to monster dens

牛さんに毎回狩られてるけど、
蟻のように、どこからもなく湧いて出てくるのだろうか