There are no vitamins or nutrients in rabbit feces, but there are many nutrients in their cecotropes, and when rabbits eat their cecotropes, it does look like they're eating their feces. See the related question below for more details.
They eat wildflowers and greens. they also eat their own feces. I know it's gross, but that's how they get some extra vitamins and minerals. (P.S. Rabbits don't always live in burrows!)
Rabbits actually excrete two types of "poop", partially digested cecals (aka "night feces") and fully digested feces. True feces are firmer and smaller, having been fully processed by the rabbit; while the feces isn't entirely odourless, it does have very little smell. Cecals are formed in the large intestines and are reingested by the rabbit in order to absorb certain vitamins and minerals; they are a little larger and moister than true feces and may have slightly more aroma. The lack of noticeable smell in either form is most likely due to the nature of a healthy rabbit's diet. Rabbits are true herbivores (plant eaters) and the high fibre content of their diet produces drier feces with little waste remaining.
No. There is no reason why rabbit feces should be radioactive, unless of course they ate something radioactive or they are under medical care using radioactive isotopes. It might be possible that if the soil is radioactive, and the plants become radioactive, that a rabbit might excrete radioactive feces from eating the plants.
Yes, rabbits do indeed eat their own feces. Rabbits are vegans, and like most vegan animals, their digestive tract is not long enough to fully extract the nutrients from what they eat. So they will eat it again. Deer tend to like to eat rabbit feces too, so if you find a pile of rabbit feces, there may be deer nearby.
Clean him up. You are his caretaker.
same reason as dogs they are lacking vitamins
If your rabbit has diarrhea or mushy or runny feces, this means your rabbit is sick and requires veterinary care. If your rabbit is a baby, diarrhea is an emergency situation and your bunny requires immediate medical care. If your rabbit is an adult, mushy or runny feces is a serious problem and your bunny should be seen by a vet as soon as possible. Please see the related questions below for details and helpful links.
Human flesh and on the rare occasion they nibble on rabbit feces.
If the "stuff" on the rabbit's bottom is feces, then your rabbit is sick. See the related link "Rabbit Butt Bath" below for more information, and bring your rabbit to a vet as soon as possible.
Although you could just put it in the trash, rabbit waste is very beneficial for your garden, like your own fertilizer.
Doesn't sound like it is droppings, sounds like worms.
Carbon dioxide from your breath, urea from urine, and excess vitamins from feces.