Why are some venomous snakes deadlier than others?

Why are some venomous snakes deadlier than others?
© iStock/Mark Kostich

An international research collaboration has answered the question of why some venomous snakes are deadlier than others.

The study investigated what causes the variation in venom potency, leading to some species venomous snakes to be more dangerous than others.

Venomous snakes

Snakes are deadly predators due to their possession of potent venoms. Some species such as cobras, boomslangs and rattlesnakes have far more venom than they apparently need, with the potential to kill thousands of their prey.

However, not all venomous snakes are as deadly as these species. The marbled sea snake has a tiny amount of very weak venom, so it is far less harmful to large animals such as humans.

There have been several competing theories about why some venomous snakes have less potent venom than others.

The global health risk of snake bites

According to Dr Chris Carbone of the Institute of Zoology in the Zoological Society of London, “Snakebites are a major health concern worldwide, with 2.7 million cases each year. 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.”

Venom potency

The new study compared records of venom potency and quantity for over 100 venomous snake species. The evidence pointed to the fact that venoms have evolved to be more potent against animals that are closely related to the species that the snake commonly eats.

Dr Andrew Jackson, Associate Professor in Zoology at Trinity College Dublin, said: “Like all substances venom is dosage-dependent. Even alcohol, coffee and water can be toxic at high enough volumes so we needed to consider how much venom different species of snake produce and store in their venom glands. 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.”

The potential biomedical applications

Dr Healy is the lead author of the study. Speaking about the next steps of the research and the potential applications, he added: “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. 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.”

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