i have given red apples, just cuz they tend to be sweeter... but i leave the skin on... they eat the entire inside and leave the skin, which means more work for me when cleaning, so i guess it would be up to u
Leave the skin. Most of the vitamins are right under the skin, and the gliders will eat all of the apple up to that point. A little more cleanup, but you've already got a mess, right?
I always peel the skin but VERY close. I don't CHOP it off.... just gently peel a thin piece.. most of the time you can even see some of the red from the skin on the 'meat' of the apple.. that's how close I peel it.