You just simply were the victim of the event spawn as others have noted due to the "You are being Hunted message". Event was active at that time.

However for future reference:

1. You can also have rare situations of creatures from one biome wandering into that of another biome when chasing its denizens. This is easier to see in the past with draugr from swamps chasing deer in the meadows or slimes doing similar. However it can happen with other creatures cross biome'n too.

2. You can also opt to double check. You map seed on this site: https://valheim-map.world As there are rare instances of maps having different small pixels of biomes embedded in that of other biomes. I've a map seed I use that has that issue with forest denizens in a large meadow area where just one small set of pixels that can spawn randomly trolls and dwarves upon it.

3. If you dislike dealing with events as a whole, you can always move between map seeds and always keeping the event to be the first one with boars and necks instead.

I have for example seeds for each boss fight goals for such a consideration and a main no bosses killed seed for similar and just look at seed map traveling as portaling if you will.