though herpetologists (fancy for study of creepin' things-type experts) are split on the issue:
first, healthy rattlers with equipment in good working order, do not always rattle.
(early stages of change)
second, some non-rattling rattlers have genetically inheritable atrophied tail muscles and/or deformed rattle tails...
(change in progress)
which may prove beneficial to long-term survival of the species.
(thousands of years from now, change becomes the norm & why the heck did they/ we ever call them 'rattlers' in the first place???)