Variable venom: Why are some snakes deadlier than others?

Date:  January 8, 2019

Source:  Trinity College Dublin

An international collaboration led by scientists from the National University of Ireland, Galway, The University of St Andrews, Trinity College Dublin and the Zoological Society of London has 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. 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.

But not all venomous snakes are so dangerous. For example, the marbled sea snake has only a tiny amount of very weak venom, making it effectively harmless to any relatively large animals such as humans. Why venoms vary so much in their ability to kill or incapacitate potential prey animals has long puzzled scientists, with several competing hypotheses suggested as explanations.

The study, which has just been published in international 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.

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