Scientists have uncovered why the venom of some snakes makes them so much deadlier than others.
Snakes are infamous for possessing potent venoms, a fact that makes them deadly predators and also strikes fear into humans and other animals alike, said researchers, including those from the Trinity College Dublin in Ireland.
However, some species, such as cobras, boomslangs and rattlesnakes have far more venom than they apparently need.
In a single reserve of venom, they have the potential to kill thousands of their prey animals and several adult humans.
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 eats.
"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 animals they are most often the target of the venom," said Kevin Healy from the University of St Andrews in the UK.
"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 Healy, who is now Lecturer of Zoology at the National University of Ireland Galway.
The research also showed that the amount of venom a snake has depends on both its size and the environment it lives in.
"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," Jackson said.
The results of the study also have potential to aid in our understanding when it comes to human snakebites.
"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," Carbone said.
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