The western diamondback rattlesnake (Crotalus atrox) is one of the best-known rattlesnakes in North America, found across the southwestern United States and northern Mexico.
Where the name comes from
Its common name comes directly from the diamond-shaped pattern running down its back — one of the more distinctive markings among North American rattlesnakes, along with the alternating black-and-white "coontail" rings just before the rattle.
How the rattle actually works
The rattle is made of loosely interlocking, hollow segments of keratin — the same material as human fingernails — at the tip of the tail. Special muscles can vibrate the tail dozens of times per second, and the segments click together to produce the buzzing warning sound.
Here's the part people often get wrong: a rattlesnake doesn't gain exactly one new segment per year. It adds a new segment roughly each time it sheds its skin, which can happen multiple times a year depending on food and growth — and older segments regularly break off from wear. That means you genuinely can't reliably tell a rattlesnake's age just by counting its rattle segments.
Range: Southwestern United States and northern Mexico · Length: Commonly 1–1.5 m · Diet: Rodents, rabbits, birds, and reptiles · Venom: Primarily hemotoxic · Habitat: Desert, scrubland, and rocky terrain