Feb. 6 (UPI) -- Venom potency varies from snake to snake, even among individuals from the same local population.
Until now, scientists thought venom varied from population to population. A rattlesnake living along the edge of a swamp doesn't hunt the same prey as a rattlesnake living among the boulders at the base of a mountain -- it makes sense that different groups of snakes would use venom adapted to their particular diets.
But according to new research, venom variation can be found among snakes living in the same place. The venom of one snake might prove deadly for one lizard but not for another, and the snake next-door might easily take down any and all lizards.
"We found differences within the same population that were almost four times greater than differences in toxicity between snakes from different regions," H. Lisle Gibbs, professor of evolution, ecology and organismal biology at Ohio State University, said in a news release. "To my knowledge, nobody has ever documented anything like this before -- we've all been focused on the snakes from different populations living in different habitats."
Gibbs and his colleagues collected venom samples from 32 pygmy rattlesnakes in Florida. Scientists tested the venom's effects on brown anole lizards, an invasive species closely related to one of the rattlesnake's preferred snacks, the green anole.
The venom from some snakes knocked out every lizard. But the venom from a few snakes proved deadly for only some lizards and harmless for others.
Researchers published their findings in the journal Biology Letters.
"It could be that the snakes that aren't good at killing these lizards are great at killing other prey, such as frogs. We just don't know," Gibbs said. "Another big question from an evolutionary perspective is 'Why aren't they good at killing everything all the time?'"
The proteins that lend venom its toxic punch aren't easy to produce, they require the snake's energy -- energy that is finite. Some snakes may devote more energy to producing proteins toxic to one type of prey but less effective for others.
"This is a whole new way of looking at how evolution operates on venom that we haven't considered," Gibbs said. "There's a new act in this evolutionary play that we didn't know about until now."