João Miguel Alves-Nunes stepped on snakes thousands of times to learn more about their bites.
The jararaca is a venomous pit viper commonly found in South America. Its venom packs a deadly mix of toxins that causes excruciating pain, life-threatening bleeding, and kidney failure. What makes this snake particularly scary even among vipers is its particularly aggressive nature. This snake will bite first and ask questions later whenever it considers itself threatened.
So, what is the threshold that triggers the jararaca's defensive behavior? Or maybe an even better question is why some snakes bite while others are chill. Biologist João Miguel Alves-Nunes reasoned there's only one way to find out: expose yourself to countless threatening scenarios — including some in which he purposefully aggravated the snakes — and see what happens.
In the process, the researcher stepped a staggering 40,000 times on snakes to push them to bite him. Miguel Alves-Nunes stepped gently on the slithering reptiles so as not to harm them, the researcher notes.
Thanks to this very brave (and even mad) initiative, the study found that the defensive behavior of Bothrops jararaca is influenced by intrinsic factors such as size, sex, and life stage, as well as environmental factors like temperature and time of day. Each of these factors significantly correlates with snakebite incidents.
Folk wisdom in the regions where the jararaca is native suggests these snakes bite only when stepped on. However, that's not entirely true. Smaller snakes, particularly newborn females, were more prone to bite defensively. Additionally, warmer temperatures increased the likelihood of biting. This means hiking in viper territory on hot summer days should be avoided.
These findings suggest that understanding the ecological and behavioral factors influencing snakebite can enhance prediction and prevention strategies.
Seeking snake bites
A jararaca in Brazil. Credit: Flickr, Márcio Cabral de Moura.
Snakebites affect millions of people globally, with the World Health Organization classifying them as a high-priority neglected tropical disease . Traditional research has focused on venom and antivenom , but this new study shifts attention. It focuses instead on the snakes' defensive behaviors, which play a crucial role in snakebite incidents.
The study, conducted by João Miguel Alves-Nunes and his team, analyzed how environmental and biological factors influence the defensive biting behavior of Bothrops jararaca . This species is responsible for many snakebites in the state of São Paulo, Brazil.
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Researchers conducted experiments with 116 snakes, including adults, juveniles, and newborns, housed individually under controlled conditions. The behavioral tests simulated human-snake encounters with steps made on or near different parts of the snake's body using safety boots.
“I stepped close to the snake and also lightly on top of it. I didn't put my whole weight on my foot, so I did not hurt the snakes.” Overall, he explained, “I tested 116 animals and stepped 30 times on every animal, totaling 40,480 steps.”
Remarkably, despite all the snake stomping, Miguel Alves-Nunes was never bitten by a jararaca, although he had a training incident with a rattlesnake.
“I felt 100% safe, and the jararaca bites never punctured [the boots]. However, when I was doing simulations with a rattlesnake, one punctured the boot, and I was bitten,” the researcher said in an interview with Science
“Thankfully, I was in the best place I could be. The Butantan Institute is a leader in antivenom development, and I was very well-assisted at its hospital. Unfortunately, I discovered that I am allergic to both antivenom and snake toxins. I had to take a 15-day medical leave.”
The tests took place in a small arena with specific time intervals. Thus they avoided stress and prevented the snakes from developing patterns that might influence the study's outcomes. Researchers used an infrared thermometer to account for variations in defensive behavior based on temperature.
Through experimental simulations, the researchers found significant correlations between these variables and the likelihood of a snakebite.
Ecology, snakes and safety implications
Warmer temperatures increased the tendency for female snakes to bite, while male snakes were less likely to bite at night under higher temperatures. Additionally, the study found that the body region touched influenced the likelihood of a bite, with contact on the head significantly increasing the probability compared to the midbody or tail.
“The smaller the animal, the greater the chance it will bite you. Another thing is that females are more aggressive and prone to bite, especially when they are young and during the daytime. We also found that the animals get more aggressive in hotter temperatures,” said Miguel Alves-Nunes.
Portrait of João Miguel Alves-Nunes holding a rattlesnake. Credit: Adriano Fellone.
These findings align with epidemiological data showing higher snakebite rates in coastal areas of São Paulo, where Bothrops jararaca tend to be smaller and temperatures higher. Snakebites were more frequent in warmer months and during times of increased human activity.
The implications of this research are profound. By understanding the ecological and behavioral factors influencing snakebite incidents, public health measures can be more effectively targeted. For example, distributing antivenom in regions and during periods identified as high-risk could significantly reduce the impact of snakebites.
While this study provides valuable insights, it also highlights the need for further research. Future studies should explore the relationship between snakebite incidents and the behavior of other venomous snake species in different regions.
There are reasons to believe the jararacas defensive behavior is similar to other vipers, but each species' behavior should be assessed individually. Whether enough snake researchers are willing to step on them thousands of times and risk getting bitten is another question. This integrative approach could lead to more comprehensive strategies for predicting and preventing snakebites globally.
The new findings appeared in the journal Scientific Reports