Do xenomorphs need to eat to survive?

The Dogalien was also seen eating in Alien 3, though I don't know if that was a deleted scene or not.

Nope it wasn't a deleted scene. I saw it on HBO(or something I don't even remember what channel it was, only that the cussing wasn't bleeped out) a while back. Like a year or two ago.

The whole eating question riddles me too. Everything that lives needs energy in one form or another as far as i know, but we have no clue whatsoever the xenos actually consume. And considering their fast rate of growth, and all that slimey stuff they produce for their hives (assuming they actually do produce that stuff in their bodies), their demands must be humongous. The xeno in Alien grew extremly fast after it's birth, but yet there were no living things he ate to satisfy all his bodies need for energy (assuming there wasn't a giant fruit orchard hidden somewhere on the Nostromo we haven't seen). Maybe it feasted a bit on the crews supplies, but it's hard to imagine all he needed were some dry instant noodles or whatever (i guess on a cargo ship which is en route for a very long period, and where the crew is mostly in cryosleep, there aren't that many diverse supplies of fresh food). He didn't even ate poor Brett after killing him.

Call me silly, but considering how different from us the xeno is, i always imaginated the xeno could consume things we wouldn't call "consumable" at all. Maybe his extremly acid metabolism isn't just a defense mechanism, acid which can dissolve matter on a molecular level can be pretty handy i guess. Maybe the xeno can dissolve things like, well ore, or metal, split up their moleculesand , his metabolism can use some of that elemental stuff or whatever as fuel. If it would be able to do something like that, it would have an almost infinitive stock of "food" on almost every location, from planets to ships. That thought always fitted for me well with all this "perfect organism" stuff.

Or maybe the beast is some sort of living perpetuum mobile and it doesn't need to eat at all, who knows.

One theory on how they thrive on so much "infinite" energy without consuming anything is that they're basically living batteries, which also explains the acidic blood. I'll have to look it up since I can't even be bothered to paraphrase this into terms that don't sound like I pulled it out of my ass.

Edit: Actually, your theory about them dissolving anything with their blood (which can explain why they can cough it up) to eat it was another thing I read somewhere, and that's completely rational thinking, considering this is Aliens we're talking about.

On the theory that they are basically living batteries, would that mean their mouths have no function besides their use as weapons? Their teeth suggest a carnivorous diet, if they were capable of eating rocks for nourishment, wouldn't they have thick, blunt teeth to actually crush the rocks for consumption? Or do you think they'd swallow it whole?

I don't recall them needing to consume anything if we're going by the battery theory, but I just don't remember for sure. I DO know that it came from a comic or book. Where the hell is DD when you need him?

I know they don't get the energy from electricity or anything, since science dictates that to be impossible (holy shit, I can't remember any specifics right now, but take my word for this), though again, these are Xenomorphs we're talking about.

Not really they only eat to eat they r not hungry

Never thought about this battery idea before, but it sounds interesting, especially if you belong to those people who like to see the xenos more as biomechanical hybrids than pure biological lifeforms. As for the science matter, i generally enjoy science-fiction where the first word of the genre name is actually really kept in mind, but i tend to be a bit clement in that department in the alien franchise - after all, they're completely alien, and it's a nice thought they might be something we can't really comprehend, or function in a way our current scientific knowledge would actually call impossible. After all, science is something which reinvents itself regularly.

@Firehunter
I don't think they would actually eat stones, but maybe they can excrete some acid in some way to dissolve matter outside of their body. Sadly, my chemistry knowledge is quite limited. I do not really know very much about acids, bases, how they work and that stuff. But something i believe to vaguely remember from chemistry class for example is that if you dissolve certain metals with acid, you actually produce some friable mineral salts in the process. Don't pin me down on that, because i actually never liked it in school, and it was way back anyway. But after all, nothing in nature really disappears, the stuff just transforms into something else. So my main thought was that the xeno would use it's acid to dissolve some massive matter outside of it's body and consume the remains.

As for the xenos beeing true carnivores, wouldn't that be a major problem for them? They need living hosts to reproduce, if they also base their diet mainly on animals and the like, they would have to split their prey. Considering they're meant to be an almost perfect species, that sounds somehow not very effective. Maybe they could be carrion eaters and eat the hosts after they're dead.
I think for the sake of effectiveness it would be more likely they're omnivores with a great variety of possible diets. Adaptability and a broad field of possible diets increases a species chances of survival, just think of those damn rats and cockroaches.

That's what interests me. That if they eat to eat or eat to live. Sci-fi u did it again that's why u r my favorite genre of books and movies. But mostly the second mouth does the work on eating it goes for the head sometimes. But what puzzles me is the movie aliens 3 why should the little girl neut and hicks die sometimes sci fi has some sick ideas. Love them:D

what about the cross species? when they hatch from preds and or other animals they have some sort of distinguished look about them. like AVp2 the alien pred

wouldnt that on a molecular level mean they have traits from their hosts? would diet also be associated with desires to eat what they came from?

i agree about the aliens acid reflex, it could be used to break down minerals but it also used as a building tool, melting and pasting things into place maybe. it uses it to probably grind up rocks but i dont think it would eat ore, anything going into the aliens mouth would have to turn into liquid, probably that way absorbed into the aliens blood stream. it would have to hack up something too solid, they are small and thin, cant really drag themselves against wall with a belly being in away. or weighing them down. i think they can just as easily eat animals by liquifying them.

needing to eat to survive? they can be like insects living for their purpose which is only a period of time and then just dying off if its just that simple.

You might be right. The reason they take traits from their host is to have a better chance at surviving whatever environment they're born in, so the fact that it was the Dogalien that was first seen eating might not be a coincidence. I'm not sure what sort of advantage hunger gives, though. That seems like a major flaw of the "trait taking" ability.