What are the requirements for the Onbu Monument (Our Friend and Protector achievement)

[DarwinX]

Made it to 100 days and I was trying for both the no berries and Onbu Monument in the same run.  I never let Onbu get more than 50% hungry.  I'm not sure about poison but definitely less than 50% and I never let him get hurt.  I tanked my productivity by destroying all my houses so I was less than 100%.  His tail has been wagging plenty and I never pulled out a spike.  No damaging buildings were constructed (or even researched).  The only thing that occurs to me is that I never pet him, so I'm not sure if there's a requirement for how many times you need to pet him.

I've also made sure that his hunger/poison/sleep was less then 20% right before hitting the dead Onbu.