Bergcube: I could be mistaken but I don't believe that'll work, at least not efficiently. You could disable recording videos by motion detection and (I think) set time lapse to record all the time, but you'd waste resources because motion always works to detect motion.
Thank you for your reply, genius3000. Resources isn't really an issue in this case, I have a laptop doing only this with one USB camera. I want a way to shoot continuously now and then, at times I know there will be activity. I could use Cheese but that generates files that are a lot larger.