What is the rattle of a rattlesnake made of?
Rattlesnake
Rattlesnake skin has  a set of overlapping scales which cover the entire body, providing protection from a variety of threats including dehydration and physical trauma.[43] The typical rattlesnake, genus Crotalus, has the top of its head covered with small scales, except, with a few species, a few crowded plates directly over the snout.[44]  The skin of snakes is highly sensitive to contact, tension, and pressure; they are capable of feeling pain.[45]