Western Diamondback Rattlesnake (Crotalus atrox) venoms show increased snake venom metalloproteinase abundance and activity at their northeastern distributional limits.

Crotalus atrox venoms show high levels of metalloproteinase activity and generally display low levels of geographic variation, but proteolytic activity is known to increase moving northeast across the distribution in the United States, inversely to venom toxicity. We tested the venoms of five individuals from the northeastern distributional limit in Arkansas and found the highest activities and abundances of snake-venom metalloproteinases compared to other assayed populations. We discuss the ecological implications of the heightened lytic activity in venoms from Arkansas rattlesnakes.