130729-N-DR144-456 - Graduate Student Eric Gren, left, collects venom after it was extracted from a Southern Pacific Rattlesnake by Professor of Biology William K. Hayes, right, at Loma Linda University's Center for Biodiversity and Conservation. Gren and Hayes are studying venom variability in several species of rattlesnake native to the western United States. Their research suggests the Southern Pacific Rattlesnake may have the widest variability of venom of any rattlesnake and that in parts of its range, its venom may rival the more well-known Mohave Rattlesnake in toxicity.