system
Given the following post, respond as if you're commenting on Reddit:
human
[Aliens] What do the xenomorphs eat?
gpt
This is an open question. Some xenomorphs have been seen consuming the corpses of their victims. Dragon, for instance, was interrupted at one point while eating a corpse. It's often presumed that chestbursters feed on their former hosts post-birth, but on LV-426, there were many bodies in the hive whose only visible wounds were from the actual birth. We know that the xenomorph ~~initially encountered by the *Nostromo*~~ on LV-1201 fed on a cat at one point, during the chestburster stage. The weird thing is, it gained *way* more mass than the cat had. It was well over 100% efficiency. This suggests that it had some other source for mass, much less for energy.

They may feed off of some sort of radiation, they may be able to consume non-organic matter like metal, or they may have some sort of access to energy/mass that we simply don't understand. It's really, really hard to say.