Both predator and prey through gaining calories up to a certain level, ascend higher in rank.
The three ranks are:
Upon selection of a animal and starting the survival game mode or procreating and gaining control of a member of your offspring, you are automatically at rookie rank, which can only mate with low quality mates.
Once the central animal has gained enough calories to progress up the ranks he or she is promoted to veteran. At this rank s/he gains the ability to mate medium quality fe/males, better known as Average mates.
If they gain another rank through the gathering of calories they will progress even further up to Boss rank, which allows you to choose the best mate depending on whether they have the needed territory to establish a nest.
Every time you rank up two your stats (life and energy) will restore to it's full amount, which offers tactical moves.
Note that if you rank up, a short unskippable animation is shown. The yearcounter does not stop during this but you are not allowed to walk or attack when it is still showing. You will get hit from normal attacks, but critical strike evade time events can occur during this. The attacker will not be allowed to strike the player, and you can dodge after the animation ends.