[yencabulator]

> Imagine if they were aware of their mortality and short relative lifespans...

Having had dogs live with other dogs growing old and passing away, I think this might be a lower threshold than understanding (a subset of) human language. Surely even without humans, a pack of social animals has individuals getting sick and growing old, and that changes how they interact with each other. Elephants are known to keep visiting bones of relatives over multiple years.

I'm personally more surprised at how well my 12-year old mutt picks up new routines, and the words that are said at the start of the routine, than at the thought that she would know that everyone's getting older and will die at some point. I'm anecdotally actually quite convinced she used to live with older people before -- she comes to "take care of me" every time I cough or sneeze.