Well now we don`t even know how many preds the predalien killed, it could have simply sabotaged the ship without attaking anyone. And about the dreads, since we see how aliens don`t get the hair from humans, but they do get the dreads from preds, i think we could assume that they are actually not molded in a painful (painful?? what the hell is painful about molding hair? it should hurt like crap when you get a haircut) ritual or so, but that, as the other thoury says, they are apendiges made of meat not hair and maybe they have some use that we will never care about.
And now about the predalien. I love it. The predalien is my favourite.
AS FOR THE AVP-R PREDALIEN, i couldn`t hate anything in that movie more. It is wrongly made and it turned a significant part of the movie into crap because that crappy predalien looks like crap. I have already compared it to several things and i have also eaten those things right after comparing the predalien to them. That predalien resembles everything i could hate the most about that movie. It has wrong mandibles, wrong dreads, a wrong colour and a wrong tail. Basically, it looks nothing like any predalien before it, and i will consider it a kind of newborn, but worse, cos the newborn has a nice face in my sig. For what i care, it could even be as ridiculous as Leandros says it should be, it`s not of my interest what the hell happens to it.