Michael & Patricia Fogden / Timber Rattlesnake (Crotalus horridus) coiled on ground among leaf litter, Appalachian Mountains, Pennsylvania

Michael & Patricia Fogden / Timber Rattlesnake (Crotalus horridus) venomous snake camouflaged in leaf-litter in the Appalachian Mountains, Pennsylvania

Michael & Patricia Fogden / Timber Rattlesnake (Crotalus horridus) newborn babies, Appalachian Mountains, Pennsylvania

Pete Oxford / Timber Rattlesnake (Crotalus horridus) showing heat sensitive pits, northern Georgia

John Cancalosi / Timber rattlesnake (Crotalus horridus) gravid female, and Northern copperhead (Agkistrodon contortrix) resting amongst lichen covered rocks, Maryland, USA. August.

Joel Sartore / Photo Ark / Close up of a Timber rattlesnake's (Crotalus horridus) tail. It is vibrating its tail as a threat display. Verve Biotech, Waverly, Nebraska. Captive.

Joel Sartore / Photo Ark / Timber rattlesnake (Crotalus horridus) performing threat display by vibrating tail, Verve Biotech, Waverly, Nebraska. Captive.

Joel Sartore / Photo Ark / Timber rattlesnake (Crotalus horridus) performing threat display by vibrating tail, Verve Biotech, Waverly, Nebraska. Captive.