Snake venom evolved for prey not protection

March 25, 2020

It is estimated that every year, over 100,000 human deaths can be attributed to snakebite from the world's 700 venomous snake species - all inflicted in self-defence when the snakes feel threatened by encroaching humans.

However, a new piece of research concludes that snake venom did not evolve as a defence mechanism.

Senior Lecturer Dr Wolfgang Wüster, a world-renowned expert on snake venom evolution at Bangor University's School of Natural Sciences explained:

"We know that snake venom is used primarily for foraging; for overpowering and killing prey. However, we also know that snakes use their venom in self-defence - that's why so many people get bitten, and sometimes killed, by venomous snakes worldwide. We wanted to investigate whether defence was a driver in venom evolution."

To provide efficient defence from a predator, the snake venom would need to provide sufficient instant pain to deter the predator and enable the snake to escape, much as a bee-sting hurts immediately.

A new paper published in Toxins reveals that surprisingly few venomous snake bites cause immediate pain, implying that the venom make-up has not evolved for a defensive primary purpose.

Bangor University student Harry Ward-Smith tested this hypothesis under Dr Wüster's supervision.

He gathered online survey responses from reptile keepers, herpetologists and fieldworkers, as part of his undergraduate degree in Zoology with Herpetology.

His survey, which gained nearly 400 responses world-wide, asked people working with snakes about the time-course of pain after bites they had sustained.

The results of around 600 experiences revealed that only a minority of bites and species regularly cause rapid, severe pain. Moreover, where early pain evolves during snake evolution, it is likely to be lost again in descendant lineages.

Dr Kevin Arbuckle, Senior Lecturer in Biosciences (Evolutionary Biology) at Swansea University's Department of Biosciences and a co-author of the paper commented:

"Our results suggest little evidence for widespread evolution of venoms driven by their use in defence, though interesting exceptions likely exist such as the defensive use of venom 'spitting' in some cobras, and these specific cases deserve further study."

Dr Wüster added:

"Even though we might have expected defending your life to be more important than feeding, it turns out that natural selection for diet does seem to be the main driver of venom evolution in snakes"

Harry Ward-Smith said:

"I'm proud to be in the minority of scientists who published their undergraduate work, writing this up took a lot of work even after graduating.

I hope studies like this start to encourage further research into the function and natural ecology of snake venom, particularly rear-fanged venomous snakes which we still know so little about."

Harry Ward-Smith 24 from Wimbledon, London chose to study Masters in Zoology with Herpetology at Bangor University because it is the only degree in the UK which specialised in herpetology. He added that a bonus of studying at Bangor was that much of the UK's best white-water kayaking was within striking distance in Snowdonia.

Since graduating Harry has radio-tracked the Green Cat Snake within the Sakaerat Biosphere Reserve, Thailand and taught at further education in the UK. He is now considering further research opportunities, quite possibly a PhD in the near future.
Contact for further information:

All images Single use only and credit Wolfgang Wüster


Image 1: Painless venom: Indian kraits (Bungarus caeruleus) are notorious for biting sleeping people at night. While highly lethal, the bites are so painless that they are often dismissed as trivial until it is too late. This indicates no defensive function for this venom

Image 2: Caption: Many snakes, like this Indian cobra (Naja naja) will use their venoms in self-defence, causing millions of bites every year. However, did their venoms evolve for this function? This new study suggests that it did not.

Image 3 Caption: Defensive venom? Some coral snakes (Micrurus) have specifically pain-inducing toxins in their venoms, suggesting that natural selection for defence may have played a role in their evolution - a possible exception to the rule uncovered in this study.

Editor's Notes:

1. Full paper: Fangs for the Memories? A Survey of Pain in Snakebite Patients Does Not Support a Strong Role for Defense in the Evolution of Snake Venom Composition

2. 584 online surveys completed. People regularly in contact with snakes were targetted as it was felt that they would be able to identify species and their familiarity with snakes would mean that they were less succeptible to fear-induced memory distortion.

3. It is highly likely that most predators would show similar reactions to envenomation to the human 'model' chosen.

4. In all snake families, mean pain levels within one and five minutes after bite were considerably lower than the maximum pain levels reported in later phases of envenoming.

5. The pain became too distracting for normal activities within the first five minutes in only 14.55% of bite victims, and later than five minutes in another 30.82%.

6. Remarkably, 54.62% reported never experiencing pain great enough to make normal activities impossible.

Swansea University

Related Pain Articles from Brightsurf:

Pain researchers get a common language to describe pain
Pain researchers around the world have agreed to classify pain in the mouth, jaw and face according to the same system.

It's not just a pain in the head -- facial pain can be a symptom of headaches too
A new study finds that up to 10% of people with headaches also have facial pain.

New opioid speeds up recovery without increasing pain sensitivity or risk of chronic pain
A new type of non-addictive opioid developed by researchers at Tulane University and the Southeast Louisiana Veterans Health Care System accelerates recovery time from pain compared to morphine without increasing pain sensitivity, according to a new study published in the Journal of Neuroinflammation.

The insular cortex processes pain and drives learning from pain
Neuroscientists at EPFL have discovered an area of the brain, the insular cortex, that processes painful experiences and thereby drives learning from aversive events.

Pain, pain go away: new tools improve students' experience of school-based vaccines
Researchers at the University of Toronto and The Hospital for Sick Children (SickKids) have teamed up with educators, public health practitioners and grade seven students in Ontario to develop and implement a new approach to delivering school-based vaccines that improves student experience.

Pain sensitization increases risk of persistent knee pain
Becoming more sensitive to pain, or pain sensitization, is an important risk factor for developing persistent knee pain in osteoarthritis (OA), according to a new study by researchers from the Université de Montréal (UdeM) School of Rehabilitation and Hôpital Maisonneuve Rosemont Research Centre (CRHMR) in collaboration with researchers at Boston University School of Medicine (BUSM).

Becoming more sensitive to pain increases the risk of knee pain not going away
A new study by researchers in Montreal and Boston looks at the role that pain plays in osteoarthritis, a disease that affects over 300 million adults worldwide.

Pain disruption therapy treats source of chronic back pain
People with treatment-resistant back pain may get significant and lasting relief with dorsal root ganglion (DRG) stimulation therapy, an innovative treatment that short-circuits pain, suggests a study presented at the ANESTHESIOLOGY® 2018 annual meeting.

Sugar pills relieve pain for chronic pain patients
Someday doctors may prescribe sugar pills for certain chronic pain patients based on their brain anatomy and psychology.

Peripheral nerve block provides some with long-lasting pain relief for severe facial pain
A new study has shown that use of peripheral nerve blocks in the treatment of Trigeminal Neuralgia (TGN) may produce long-term pain relief.

Read More: Pain News and Pain Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to