The environment holds the key: study
Scientists have uncovered why the venom of some snakes makes them so much deadlier than others.
Some species, such as cobras, boomslangs and rattlesnakes, have far more venom than they apparently need. Why venoms vary so much in their ability to kill or incapacitate potential prey animals has long puzzled scientists.
The study, published in the journal Ecology Letters , tackled this puzzle by comparing records of venom potency and quantity for over 100 venomous snake species, ranging from rattlesnakes, cobras and the tree-dwelling boomslangs of Africa to sea snakes and burrowing asps.
The team found strong evidence that venoms have evolved to be more potent against animals
that are closely related to the species that the snake commonly ate. “These results make sense from an evolutionary viewpoint as we expect that evolution will have shaped venoms to be more efficient at killing the prey,” said Kevin Healy from the University of St. Andrews in the U.K.
“You won’t find many mice in the sea so we wouldn’t expect a sea snake to evolve venom that is more effective at killing mice than fish,” said Mr. Healy.
The research showed that the amount of venom a snake has depends on both its size and the environment it lives in.
“Like all substances venom is dosage-dependent,” said Andrew Jackson, Associate Professor at Trinity College Dublin. “We found that big terrestrial species have the most venom, while smaller tree-dwelling or aquatic species had the least.”
“This difference may be due to how often a snake encounters its prey in these different environments, with terrestrial species requiring a larger reserve of venom to take advantage of the rarer opportunities to feed,” Mr. Jackson said.
“Snakebites are a major health concern worldwide, with 2.7 million cases each year,” said Chris Carbone from the Zoological Society of London. “Understanding how venom evolves may help us better identify the risks to humans from different snake groups, and also potentially from other venomous animals such as spiders, scorpions, centipedes and jellyfish,” he added.