Apply gravity to bones?

Hi,

I have a sphere and I have an object which is similar to a snake laying on top of the sphere.

The snake has a blender armature, but I'm not sure how I can make this work so that the tail of the snake will stay flush to the surface of the sphere as the snake moves around. I'm guessing that I want to somehow have gravity applied to each bone? I did add a rigidbody to the last bone to test this, but this just gave some strange results (the tail shot down through the spheres collider as it it wasn't there.

If Anyone can give me any tips on how I can have each bone part of the model respond to gravity I'd really appreciate it!

Thanks.