it usualy is a case of i want the food u have
with snakes the food someone else has is "better"
usualy they eat each other while feeding or shortly after.
u sure u didnt feed them?
because when 1 snake starts with eating on side of the meal
and the other 1 starts on the other side
one wil be eaten unless u take them appart
cant think of anything else
cause none of the thamnophis family have cannibalism in their nature as far as i know
grtz richard