Each year, approximately 8,000 Americans are bitten by venomous snakes. On average, 800 or so bites occur annually in California, home to an abundance of snake species, but only one is a native species with a highly toxic venom; rattlesnakes. In particular, the Western Diamondback Rattlesnake.
Toxin levels in rattler venom vary from year to year and season to season, but typically venom is weaker in winter and stronger in summer because snakes are more active, fighting for food and territory. Toxicologists are seeing a rise in the toxicity of the venom and are not certain why it is becoming increasingly potent. Some scientists suggest that with the modern world encroaching on habitats, it is just survival of the fitest.