The rattle of the #rattlesnake is made up of a protein called keratin, the same protein that your hair and fingernails are made of. A new segment is added each time a rattlesnake sheds, but they can shed at different rates. A rattlesnake can move its rattle back and forth 60+ times per second. #reptilesrule #staringcontest #sandiegozoo (📷: Paul Manaig)