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Snake venom has not developed for self-defense, new study results



  A western rattlesnake with a diamond back (Crotalus atrox) in a defensive stance.

A western rattlesnake with a diamond back (Crotalus atrox) in a defensive pose.
Image : Wolfgang Wüster

Snakes use their venom for both offensive and offensive purposes for defense purposes, but new research suggests that this ability originally appeared as a strategy for attacking prey, not for self-defense.

An unresolved question about the evolutionary origin of the snake venom is whether these limbless reptiles were originally acquired for their poisonous powers for offensive or defensive purposes. That their venom was created for defense purposes is hardly an idea, given the amount of human suffering that these venomous snakes regularly cause.

Figures from the World Health Organization show that about 2.7 million people are bitten by venomous snakes each year, of which 81,000 to 138,000 will die. Needless to say, snakes don't hunt people, but they will strike when threatened.

Snakes clearly use their poison for self-defense e. But did poison first appear as a protective measure and later develop as a means to subjugate prey, or was it the other way around? New research results published in the correspondingly named journal Toxins deal with this question and find that poison is probably for prey and not for defense has developed. E.

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“We know that snake venom is mainly used for foraging. for overpowering and killing prey, ”said Wolfgang Wüster, co-author of the new study and researcher at Bangor University, in a press release from . "However, we also know that snakes use their poison for self-defense. That is why so many people around the world are bitten by venomous snakes and sometimes killed. We wanted to investigate whether defense is a driver for poison development."

   Brazilian Caissaca, a snake with a particularly painful poison. Brazilian Caissaca, a snake with a particularly painful poison.
Image : Wolfgang Wüster

In order to be effective as a defense weapon, Venom must be quick and with sufficient severity act to act as a deterrent. Bee stings are a good example.

For the new study, Wüster and his colleagues examined a variety of venomous snake bites as perceived by humans, both in terms of the time the pain was in [1945901111] and the severity of the pain.

In order to obtain the required data, di e Scientists conducted an online survey of people who regularly deal with and are bitten by poisonous snakes, including zookeepers, ecologists and herpetologists. These snake victims were asked to rate their pain experience in the first one to five minutes after the sting which they did on a scale of 1 to 10 and then after five minutes. Respondents were also asked to rate the maximum amount of pain they felt at any point in time for example a few hours later.

"The purpose was to focus primarily on the time scale of pain development and not on actual pain levels themselves," said Wuester and study co-author Kevin Arbuckle of Swansea University in an article written for The Conversation. “The basic principle was that the intensity of pain experienced will vary widely between people, but the time at which pain develops should be more consistent. Different people may consider a bee sting as a minor annoyance or unbearable, but everyone agrees that it hurts immediately. “

In total, researchers received 368 responses from people around the world, recording 584 individual bites from 192 venomous snakes.

Survey results showed that very few snakes have poison that provides an instant strike. Only 14. 5 percent of the bite victims had disruptive pain within the first five minutes, a time window that the scientists described as an “ecologically decisive” time period for the poison as a defense weapon. About 31 percent of respondents said the pain was severe after the five mark, and surprisingly, 54.6 percent said they “never had pain large enough to make normal activities impossible to make, ”the authors wrote in the study.

The scientists took this as evidence that poison occurred primarily for offensive purposes and not for protection purposes.

"Our results show little evidence of widespread development of poisons due to their use in defense, although there are likely interesting exceptions, such as the defensive use of poison" spitting "in some cobras, and these Special cases deserve further investigation, "said Arbuckle in the Bangor University press release.

"Even though we expected the defense of your life to be more important than feeding, it turns out that natural food selection appears to be the main driver of venom development in snakes," added Wüster.

There are a few limitations to this study.

First, and as the authors wrote in the study, “the pain experienced by different people bitten by the same species was very different not only in their absolute level, but also in their trajectory. ”Of course it would have been nice to see consistency here, but it is fair to say that different people experience pain differently because pain can be subjective. Yes, the authors said the course of pain was a better measure than the severity of the pain itself, but the lack of consensus is unsatisfactory here.

In addition, the new paper does not tell us much about how non-human animals react to poisonous snake bites. From what we know, smaller animals such as birds, raccoons, coyotes, and even other snakes experience the pain of venomous snake bites much faster and more intensely than humans. Future research should consider this possibility.


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