Boars can leap over logs, not sure how.
It's one of the few unique moments in Valheim I regret so much not recording because it looked so metal. I was walking in the meadows chopping wood when I walked downhill to chop a log that rolled down. When I get close a boar I didn't see because it must've been right behind it leaps over it and attacks me.

I don't think it's a "natural" mechanic of the game though.