this is the same thing i've said multiple times in 
inner party / PM's q.q... #ignoringmylove
Tusk Romp only does 42 damage in return with 12
grievous through your defences (or it's red, i've not 
cared to test that sorry)... however now n then at 
random an animal will hit you through your 
defenses for 150 SHP and like 40 or so HHP. This is 
reduced only by armor, no weight stops it. I've been 
hit by this very reliably when fighting cows during 
taming and it seems to be linked to peace mode. 
I was chasing a boar that was peace mode, went
in for a combat discovery while it had no stances
up and got 150'ed (no armor). I was taming a cow
and after a peace mode it hit me for 137 randomly
even when i had yellow blue n green up (armor on).
Then another cow was spamming between peace
and war when i was playing with it in taming...
when another 137 popped up. same number. reduced
from 150. I had my red defense up this time. All of
my defensive weights were ignored. The only thing
i noticed that last time was a call of the wild had 
ended while it was in peace mode... but i think that
was just a coincidence. 
It's not all your SHP, it's just always 150 base, whether
or not that's enough to KO you doesn't matter so much.
Haven't pinpointed it exactly coach, sorry.
I met boar which aggroed on me, i started running, he used some kind of stealth skill, dissapeared, i kept running and boom ninja boar koed me ;<
Occasionally when an animal hits an object it will appear
as if it has stopped moving or disappeared, when it is
really chasing you the whole time.