6f722013_Kids__Idaho_Public_Television___FACT
[MYTH] The number of rattles on a rattlesnake tells the age in years. [FACT] 
A rattlesnake can shed its skin several times per year, so although this does create a new rattle with each shedding, it is not representative of a year's time period. Older rattlesnakes can lose rattles in battle or while hunting food, as well.
Snake Facts - Dialogue for Kids (Idaho Public Television)
FACT