Continuity mistake: The film opens with a girl writing on a notepad. The first shot from above shows that she's writing on the middle of the pad. Cut to a close-up of her hand and she's writing on the left side of the pad, very close to the edge. (00:01:00)
Continuity mistake: The private who was being injected with the blood substitute explodes, splattering red goo all over the glass panel. The amount increases in shots from outside the room, covering the entire panel. (00:14:45)
Continuity mistake: At 1:02:38, you see that the front door is closed. The scene after, when Lionel goes out of the water tank where they were hiding, the same door is now wide open. Then a bat scares him, and you see that the door magically closed back. (01:02:35)
Answer: Just like the humans, he had a fear of becoming extinct.