Yes, I've seen that around the edge of the swamp the swamp critters regularly kill the prey animals for me, but don't 'eat' them so leaving for me a ready supply of happy meals.

It would be great, and quite an accomplishment, if Valheim would function outside of the player view and the player simply be a part of that system.

things dont grow while you are away , they grow faster when you have been away and show up , but if you were not there they would not grow at all ,,,,,,,

Tamed wolfs in the open meadows do multiply on their own (as long as the area is loaded).
https://steamcommunity.com/sharedfiles/filedetails/?id=2928442479

Yes, to a pretty negligible degree, Valheim works independently of the player -- fires consume wood, rain makes wooden floors rot, plants grow, and, yes, if the player is in range, warring factions will have a go at one another. Players with poor aim, parry or dodge skills can lure a hard-to-kill creature to its enemy and just observe the fight from afar. Players can then finish off the weakened creature more easily.

Creature types are grouped by "factions". Creatures that are the same faction won't attack each other but creatures that belong to different factions will. This is why wild boars and tame boars won't attack each other and wild wolves won't attack tame wolves.

Leeches are living creatures but they are classed as undead in game so that skeletons and draugr won't attack them and vice versa.