It is impossible to make more than the wildest guess at how many they kill,but they are hungry creatures,not content wit

It is impossible to make more than the wildest guess at how many they kill,but they are hungry creatures,not content with only three meals a day
我的问题是but转折后but they are hungry creatures,not content with only three meals a day
为什么hungry creatures后面直接可以跟not content with only three meals a day 这句话是什么语法成分>?,
我的理解是第2句not content with.a day 为了避免重复 省略了they are 还有一种理解就是not content with...a day 作原因状语 但是原因状语接在句子后面的很少见 不是很确定.希望高手能讲这里的语法讲给我听听
我在语法书上看到这句话是作状语.什么状语请问
not content with three meals a day,they are hungry creatures
not content with three meals a day 是否是原因状语从句>?放在后面?