Jararaca (Bothrops jararaca); Photo by Frederico de Alcântara Menezes

The Species

Although there are no wild jararacas (Bothrops jararaca) anywhere within about 8,000 kilometres of Canada, you may have a personal connection to this snake: ever since 1965, the venom of the jararaca has been used to create some of the first medicine for high blood pressure and other heart conditions, up to and including congestive heart failure. This means if anyone you know has taken heart medication in the past 55 years, this snake’s venom has likely been helping them to live a healthier life, if not as an ingredient in their specific medication, then at least by pioneering the field of heart and blood pressure medicine in general.

The jararaca ranges from southern Brazil into northern Argentina and west into Paraguay. Within this area, it is predominantly a forest-dwelling snake, feeding and breeding during the wet season and much less active when the weather becomes drier. The snakes mostly use the forest canopy as a nursery, mating in the treetops and giving birth to live young in the higher branches; there the juveniles can safely hide from predators and feed on frogs. The adults usually live lower down and feed on rodents on the forest floor. The jararaca largely avoids humans by keeping to the forests and being active mostly at night, however, this snake is known to foray into the urban landscapes around São Paolo.

The Locale

Downtown São Paulo. Photo by Mateus Hidalgo. Inset: jararaca range of Southern Brazil, Paraguay, and northern Argentina. Photo by R. Altenkamp.

Located where the Tiete and Pinheiros Rivers meet, São Paulo is the largest city in Brazil, the largest city in both the Southern and Western hemispheres, and by some estimates, the fourth largest city in the world. Because so many smaller cities have run together with and been absorbed by São Paulo, population is hard to determine, but ranges between 11 million and 32 million, depending on what you include in the city limit. That’s an enormous number of people living as neighbours to the Jararaca no matter how you count!

Despite the fragmented nature of the urban landscape, a diverse assemblage of snakes can still be found. In all, 38 snake species are known to live in and around São Paulo, and the Jararaca is the third most common, making up roughly 16% of the total snake population. In certain state parks and nature reserves, the Jararaca may be the most common snake of all, with up to 70% of snakes found by visitors and scientists being Jararacas. Interestingly, Jararacas living in urban forest fragments are able to live well enough on urban rodents to survive and grow, while their predators struggle to survive in the city. These urban snakes can live longer lives and reach greater sizes than snakes living in natural forests, despite their urban habitats supporting relatively fewer prey items!

The Methods

Aerial image of Sao Paolo, showing the relatively small size of urban forest fragments inhabited by the jararaca (circled in red). Map from Siqueira and Marques 2018 in Journal of Herpetology.

The venom of the jararaca has been extensively studied, resulting in the discovery that it can be adapted into heart medication, and that bites from female snakes are more dangerous than from males.

Bites were common and often deadly during early expansions of the city, prompting the Instituto Butantan to accept donations of live snakes to study their venom and seek an antidote. Today, however, 99.3% of jararaca bites result in a full recovery. The Instituto Butantan has been taking in captured snakes since 1906 to extract venom for use in creating antivenin, and later medication. As well as helping people with heart conditions, certain elements of the venom also act as a coagulant, stopping heavy bleeding and saving people from severe injuries.

Through extensive study, the different parts of jararaca venom became better understood, which allowed compounds to be isolated for their individual effects. When the compounds that acted on the heart were identified, those that created useful effects were purified and diluted to create the effect, such as lowering blood pressure, just the right amount to turn the venom from something dangerous, to a tool for living healthier lives. Now there is ongoing research into other potential uses for the venom from this and other snake species, including destroying cancer cells!

Final Thoughts

The jararaca is a shining example of the benefits of tolerating and embracing vipers as neighbours: they and their venom (carefully modified, of course!) have saved countless lives through heart medication. More recently, the venom of one of the jararaca’s closest relatives, the jararacussu (Bothrops jararacussu), is showing promise in other medications, including treating COVID-19 by stopping viral replication. The whole jararaca family is now proving to be quite helpful!

“With increased understanding, we too might appreciate venomous snakes as living symbols of wilderness; perhaps we can even afford them a place in modern landscapes.”

Harry W. Greene

Find out more about the Jararaca in São Paulo:

Diversity, Natural History, and Distribution of Snakes in the Municipality of São Paulo (https://bioone.org/journals/South-American-Journal-of-Herpetology/volume-6/issue-3/057.006.0301/Diversity-Natural-History-and-Distribution-of-Snakes-in-the-Municipality/10.2994/057.006.0301.short)

Effects of Urbanization on Bothrops jararaca Populations in São Paulo Municipality, Southeastern Brazil (https://www.jstor.org/stable/26792526?seq=2#metadata_info_tab_contents)

Mating up in the trees: a new reproductive behaviour in Bothrops jararaca (https://www.biotaxa.org/hn/article/view/63800/68435)

Vulnerabilities in snakebites in Sao Paulo, Brazil (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4641465/)

Connor Ferguson

Field Technician – Ojibway

Connor recently joined Wildlife Preservation Canada as a Field Technician with the massasauga rattlesnake team, working on monitoring and improving snake habitat to complement his previous species at risk reptile experience with skinks and turtles across Ontario. He completed the Ecosystem Restoration program at Niagara College to earn his graduate certificate.

Jonathan Choquette

Lead Biologist – Ojibway Prairie Reptile Recovery Program

Jonathan manages the recovery program for the Ojibway population of the massasauga rattlesnake in Southern Ontario. Jonathan’s research interests lie in the field of urban herpetology, having studied both biology and landscape architecture at the University of Guelph. Jonathan has authored or co-authored numerous reports and publications about the conservation of Canadian reptiles and amphibians in urban environments.

Jonathan Choquette