the swimming pool scene, the alien just "toungue bites" one of the dead bodies several times.
Ok i want to get away from all of you's obcession that the alien is not a living being but just a weapon. Firstly there is no canon to say whether or not the alien is a weapon its just Weyland-Yutani's idea that it could be used as a weapon. Secondly in Alien the scene where Dallas is cocooned to the ship was originally to say that the Alien was going to eat him.
The Alien is a living organism and so will need sustinence, this whole idea of recharging batteries is a load of BS. Anything living needs energy to survive. You guys will proberly turn around and say that the Alien is photosynthetic next time.