Ah. Got it. If you can't pull them out to weigh them I'm not sure how you'd pull them out to feed them honestly. So, I'll have to defer to those smarter than me. I've always weighed my babies (I used the towel covering for my one feral mom so I could get in there) as that's the only way I know to figure out whose gaining and who isn't. I know people who don't and just let nature take its course though!