The jararaca is a venomous pit viper common in South America. The venom contains a deadly mix of toxins that cause 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 if it feels threatened.
So, what is the threshold that triggers the jararaca’s defensive behavior? Or perhaps an even better question is why some snakes bite while others are cold. Biologist João Miguel Alves-Nunes reasoned that there’s only one way to find out: expose yourself to numerous threatening scenarios — including some in which he purposefully aggravated the snakes — and see what happens.
The researcher stepped on snakes no fewer than 40,000 times to provoke them to bite him. Miguel Alves-Nunes carefully stepped on the slithering reptiles so as not to harm them, the researcher noted.
Thanks to this very courageous (and even crazy) initiative, the research showed that the defensive behavior of Bothrops jararaca is influenced by intrinsic factors such as size, sex and life stage, but also by environmental factors such as temperature and time of day. Each of these factors correlates significantly with snakebite incidents.
Popular wisdom in the regions where the jararaca is native suggests that these snakes only bite if stepped on. However, that is not entirely true. Smaller snakes, especially newborn females, were more likely to bite defensively. In addition, the warmer temperatures increased the chance of biting. This means that walking in viper territory on hot summer days should be avoided.
These findings suggest that understanding the environmental and behavioral factors that influence snakebites can improve prediction and prevention strategies.
Looking for snakebites
Snakebites affect millions of people worldwide, with the World Health Organization classifying them as a high-priority neglected tropical disease. Traditional research has focused on poisons and antidotes, but this new study shifts the focus. It focuses instead on the snakes’ defensive behavior, which plays 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 snake bites in the state of São Paulo, Brazil.
Researchers conducted experiments with 116 snakes, including adults, juveniles and newborns, which were housed individually under controlled conditions. The behavioral tests simulated encounters between humans and snakes, involving steps on or near different parts of the snake’s body using safety boots.
“I stepped close to the snake and also went lightly on top of it. I didn’t put all my weight on my foot, so I didn’t hurt the snakes.” In total, he explained, “I tested 116 animals and stepped on each animal 30 times, a total of 40,480 steps.”
Remarkably, despite all the snake stomping, Miguel Alves-Nunes was never bitten by a jararaca, although he did have a training incident with a rattlesnake.
“I felt 100% safe, and the jararaca bites never punctured (the boots). However, when I did simulations with a rattlesnake, one pierced the boot and I was bitten,” the researcher said in an interview with Science.
“Luckily I was in the best place I could be. The Butantan Institute is a leader in antivenom development, and I received very good help at its hospital. Unfortunately, I discovered that I am allergic to both antivenom and snake venom. I had to take fifteen days of medical leave.”
The tests took place in a small arena at specific time intervals. In this way they avoided stress and prevented the snakes from developing patterns that could influence the results of the study. 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 female snakes’ propensity to bite, while male snakes were less likely to bite at night at higher temperatures. Additionally, the study found that the body area touched influenced the likelihood of a bite, with contact on the head significantly increasing the likelihood compared to the mid-body or tail.
“The smaller the animal, the more likely it is to bite you. Another thing is that females are more aggressive and prone to biting, especially when they are young and during the day. We also discovered that the animals become more aggressive at higher temperatures,” says Miguel Alves-Nunes.
These findings are consistent with epidemiological data showing higher rates of snakebites in coastal areas of São Paulo, where Bothrops jararaca tend to be smaller and temperatures are higher. Snakebites became more common in the warmer months and during times of increased human activity.
The implications of this research are profound. By understanding the environmental and behavioral factors that influence snakebite incidents, public health measures can be targeted more effectively. For example, distributing antivenom in regions and during periods identified as high-risk could significantly reduce the impact of snakebites.
While this research provides valuable insights, it also highlights the need for further research. Future studies should investigate the relationship between snakebite incidents and the behavior of other venomous snake species in different regions.
There are reasons to believe that the defensive behavior of the jararacas is similar to that of other vipers, but the behavior of each species must be assessed separately. Whether enough snake researchers are willing to step on it thousands of times and risk being bitten is another question. This integrative approach could lead to more comprehensive strategies for predicting and preventing snakebites worldwide.
The new findings appeared in the journal Scientific reports.