The stomach acids in a snake can digest bones and teeth but not fur or hair.
Snakes do not crunch or break up bones before eating. Instead, they swallow prey whole. As the food works through a snake's digestive system, the bones slowly begin to dissolve.
If the snake is venomous, this poison assists the process. When a snake bites prey, it will chew, releasing more and more venom. This starts to dissolve the prey from the outside in, making it easier to digest. A nonvenomous snake will typically asphyxiate its prey. This may shatter bones and make them easier to process.
Whatever the breed of snake, the food eventually reaches their stomach if not regurgitated. This enables various acids and enzymes to break down the food over days.
Snakes are very lethargic during this process, as undigested food applies pressure to their internal organs. Once the bones have completely dissolved, they will be assimilated into a snake's stomach. After several days, the leftovers will be excreted as waste.
No breed of snake is capable of digesting fur. The same also applies to feathers. No amount of venom or stomach acid will break down animal fur for a snake. This is why frozen rodents sold as food for captive snakes are hairless.
A pet snake that has spent its entire life in captivity may struggle to process fur. These reptiles will be used to crunching through smooth and hairless prey. If your snake tries to adapt to furry prey, they may struggle with their digestion.