student preds eat whatever students they can find when they are hungry, some alpha preds can eat the others but have certain conditions needed to eat each other
the common requirements are: the pred being eaten must not be chasing you, stunned, or digesting something and the pred eating them must bump into the other one while chasing you and it is a chance, not a guarantee, in the 30%ish area
other conditions that I have gathered from testing:
Tulpy is so small all preds can eat her even when she has a student in her, easiest way to get rid of her is have her eat a student and piss off another pred and camp behind her like any other student
Bella can eat Satie so long as both are empty and Satie has no weight gain (weight gain adds some mass to the target and slows them down while increasing escape chance as far as I can see, there is also a margin of error here as I've gotten Bella to eat Satie while Satie only has a crazy apple in her)
Satie has never eaten non-Tulpy alpha preds under any condition as many ways as I've tried, because her capacity seems to be 3 or 4 while the other 2 large alphas are at mass 5 (Bella) and 7 (Ligeska)
Ligeska can eat both bella when both are empty and Satie so long the total capacity is less than or equal to 1 student