What makes a king cobra bite deadlier than an adder’s? Its diet

Irish and UK researchers have helped solve the mystery of why some snakes are deadlier than others, finding the answer in what they eat.

Not all snakes are created equally, at least when you take into account their ability to kill. While an adder – as found in the UK – can kill small animals or cause sickness in humans, the king cobra can kill anyone who comes across its path.

But why are some snakes deadlier than others? To help solve this mystery, researchers from NUI Galway, Trinity College Dublin, the University of St Andrews and the Zoological Society of London compared records of venom potency and quantity for more than 100 venomous snake species.

In a paper published to Ecology Letters, the team looked at species from rattlesnakes, cobras and the tree-dwelling boomslangs of Africa, to sea snakes and burrowing asps.

This led to the discovery of strong evidence that venoms have evolved to be more potent towards animals that closely relate to their diet. So, for example, venom found in the aquatic coral snake was deadliest when measured in fish, but failed to do much damage to mice.

“These results make sense from an evolutionary viewpoint as we expect that evolution will have shaped venoms to be more efficient at killing the animals that are most often the target of the venom,” said Dr Kevin Healy, a lecturer in zoology at NUI Galway. “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.”

Could help treat snake bites

The research also showed that the amount of venom a snake has depends on both its size and the environment it lives in. While big terrestrial species have the most venom, smaller tree-dwelling or aquatic snakes have far less.

The findings could help better aid our understanding of snake bites and how we respond to the estimated 2.7m cases each year across the world, as well as exploring the effects of other venomous animals such as spiders, scorpions, centipedes and jellyfish.

“The next step is to see how well this model may predict the potency of venoms in groups that have yet to have their venoms tested,” Healy added. “By using ecological and evolutionary data for available species, we may be able to use our approach as a tool to identify other species which may have properties in their venoms that are useful for biomedical purposes, such as drug development.”