In the animal kingdom, any hunt for a meal or encounter with a predator is a matter of life and death. To survive both, animals have evolved a multitude of weapons, of which venoms may be one of the most widespread and effective.

But building a chemical weapon presents an evolutionary dilemma. Should venom be optimised to disarm prey, or to cause rapid pain to deter predators? Our new study suggests that in snakes, a meal comes before self-defence.

Venoms are complex chemical cocktails. Their composition is shaped fundamentally by their intended purpose. Predatory venoms disrupt multiple tissues and organs at once to immobilise prey. On the other hand, defensive venoms have only one job: to cause rapid, intense pain to deter predators. Think of a bee sting, for example.

These differences create a conundrum. What if an animal wants to use its venom for both predation and defence? This is not a trivial question, because the storage capacity of venom glands is limited, and producing venoms is thought to carry an energetic cost. That opens the door to an evolutionary trade-off: investing resources into one function might leave less for the other.

Venomous snakes are probably the best-studied venomous organisms, and for a good reason.........

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