Why do they kill

SPEARFISH - Perhaps the Alien is designed specifically to "wipe the slate clean"? It could be that its sole function is to erradicate life. :)

@spear that perfect organism killing machine is from alien movie cannon or franchise.

Good point from a cannon perspective.  It just flys in the face of "perfect".  Perfect includes durability. 

So, maybe the beast has a short lifespan, that is something the movies should have explained.   If so, the beast is a short term assassine.  That is a different film/plot.

SPEARFISH - It could very well be that the Alien is hardwired to kill wantonly - without reasoning behind its actions.

@Something Real:. It seems you are correct.  But I would argue with Ash the the beast is perfect.  It's not durable.

SPEARFISH - I understand and wholeheartedly respect your stance. Perhaps being a "Perfect Predator" can also mean being able to kill time and time again swiftly and without detection - thus eliminating the need for high durability? Somewhat like a military assassin?

Fair enough.  If it has no sense of self then we can conclude once it has an advantagous relationship with it's environment it goes towards reproduction vs killing.  Is it to much to ask for a book/movie  to explain this???

Dr. Curt Connors

Forgiveness has and will always be an important, key and vital element of Native Culture.
TY for what you said, I appreciate it, but that was the past and these days we try to look toward the future.

That said, and getting back to Xenological Nutrition Choices... :D

I've been pestering hubby, and a friend of mine who has relevant Degrees, in how (pseudo-realistically) anything can grow so insanely fast.
Well, to grow, they all need to eat. Energy and material/structural requirements cannot be met by breathing. :D
That's hard physics, universe-wide.

They would have to possess nearly 100% efficient digestive systems, and extremely efficient metabolisms as well.
Their appetites would be constant, and would explain their extremely high levels of aggression.
Ever seen how ferocious a hungry weasel is? Same idea, just bigger, and with more drool. :)

They would have quite little emitted body heat as such a creature wouldn't be able to afford to waste so much energy, so they'd be room-temperature on average owing from the super-efficient metabolism.

@Blackwinter-witch    You're welcome

DR. CURT CONNORS - The brush with which you paint leaves a very large stroke.

@Something Real    Thank you

DR. CURT CONNORS - May statement was a negative observation, not a statement of praise.

Oh well thanks, I don't like to paint so. You believe what you want to believe, I'll believe what I believe. You think what you think is right, I think what I think is right. You have your opinion, I have mine. That's what this site is about, people's opinions. Some you're gonna like, some you're not. The world is far from perfect, it's actually pretty awful, full of a lot of awful people. Shit I got a long way to go but I see the world through my eyes and through the people I love's eyes. And nothing is gonna change the way I see it, when I think something isn't right or I don't agree with something I am allowed to say what I think. So watch out for my large brush stroke I guess. I stayed off this site for over 2 months just came back on last night after I saw one of the most disappointing movies I have seen in a long time and am here to voice my displeasure. Stayed away cause a lot of people on here just can't take a different opinion than someone else and it turns into a dumb argument. I'll probably be gone from here soon for a long time so don't worry you won't have to put up with me for that long.

Hey guys and gals, didn't Dan O' Bannon's original script hint that the Big Chap had been plundering food from the ship's galley? Also, there was supposed to be a scene where the character named Faust sees the beast knawing on a bone from a fresh kill. I realize that this never made it into the finished film, but I could've sworn I'd read that. I remember the script stating somewhere that when the beast was "hidden" on the Narcissus, that it had stowed into the background machinery to die peacefully, but this was removed from the script so as not to make the beast appear weak. 

Wasn't the original idea that it only had around a 72-hour lifespan? If so, this would explain it's need to secure hosts for egg morphing (Brett in the deleted cocoon scene) and to have a viable host ready for the newly formed facehugger (Dallas in the same scene). 

I do recall the quadrupedal Alien from Alien 3 doing what looked a lot like eating/biting on one of it's fresh kills during the leadworks scene. Maybe it's eating habits/needs depend on what type of creature the host was? 

Specifically going from alien cannon and the prequels never got an answer but...

in alien as someone pointed out Dallas and the other guy were not stowed for food. They never showed the alien eat anything. It didn't live that long anyway.

in Prometheus there were no aliens save the deacon and whatever that was like ten seconds of screen time.

in covenant the neomorphs ate or at least it looked like it was eating the woman. The other alien never lived long enough to find out.

Thats what we know. Basically it could eat glue at this point or paint chips...

Outside of ideas discussed during filming or in the original script, the answer to the OP's question is in the first movie:

Ash: You still don't understand what you're dealing with, do you? The perfect organism. Its structural perfection is matched only by its hostility.

Lambert: You admire it.

Ash: I admire its purity. A survivor...unclouded by conscience, remorse, or delusions of morality.

Pretty sure this is why Ripley and others in the series use weapons on the species instead of picking up a guitar and singing Cumbiya to the xenomorphs in the hopes they all will live in perfect harmony and buy each other a Coke.

This is seriously the weirdest thread on this forum...which is really saying something for this place LOL!

BZ 

I always presumed that as predators, the Xenos killed anything they perceived to be a threat. The face hugger and chestburster are both extraordinarily aggressive in their pursuit of survival and completing their instinctual goals of implantation and growth, so it stands to reason that the mature Xeno would be equally, if not more aggro... kind of like someone on steroids.