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See What's Inside a Rattle Snake's Rattle

FILE - This June 5, 2000 file photo shows an eastern massasauga rattlesnake curled up in the tall grass at Carlyle Lake in Carlyle, Ill. Wildlife researchers say a fungus rarely seen in the wild is killing southern Illinois rattlesnakes that already are in decline. Wildlife veterinarian and University of Illinois visiting instructor Matthew Allender says that in 2008 biologists reported to him that they'd found three eastern massasauga rattlesnakes with debilitating fungal infections in a southern Illinois park. The snakes died within three weeks of their discovery, and a fourth snake with the fungus was discovered in the same park in 2010. (AP Photo/Seth Perlman, File)

This noise means danger!