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In the new study, published in the journal Public Library of Science Biology, Dr Hanifin has now examined this arms race in detail.

His team tested the toxicity of newts and the resistance of snakes in 28 locations. They found that most areas with the most toxic newts also had the most resistant snakes, as would be expected from this tit-for-tat pattern of natural selection.

In about a third of the sites, however, even the least resistant snake was able to eat the most toxic newt. “In these areas, I think the snakes have won,” Dr Hanifin said.

The victory has gone to the garter snakes because only a few genetic changes are needed to confer substantial resistance, while the genetic mutations needed to boost TTX production among newts are more complicated.

On top of that, there are natural limits to TTX synthesis among the newts that seem to have been reached in some places.

It is possible, however, that the garter snakes will eventually lose some of their resistance, bringing the newt toxins back into play again.

The most resistant snakes are also a little slower than the less resistant reptiles, which puts them at an evolutionary disadvantage.

In the areas where all the snakes can eat newts, the slightly less resistant ones will be favoured by natural selection, and should become more common over time.

Toxic table-toppers

— The poison in the puffer-fish is said to be about 1,000 times deadlier than cyanide. The fish is considered a delicacy, known as fugu, in Japanese cuisine and chefs must be specially trained to prepare it

— The skin of the adult golden poison frog, the deadliest of the poison dart frogs, has enough toxin to kill 100 adult humans

— The venom from one bite from the taipan snake could in theory kill 100 fully grown men, but there have been no known fatalities

— The Brazilian wandering spider’s venom is more potent than that of the black widow. Strangely, a side-effect of being bitten has led scientists to consider adapting the venom as a natural Viagra

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