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Zoology

The mother of all jararacas

The ancestor of the snakes that cause most accidents in Brazil was small and had a varied diet.

Ricardo Sawaya/Butantan InstituteMeal of the day: the jararaca-de-alcatrazes (on the left) eats centipedes, whilst the jararaca-comum prefers mammalsRicardo Sawaya/Butantan Institute

The serpent that gave origin to all jararacas – the number 1 – must have arrived in South America between 11 million and 20 million years ago. Probably it came from Central America, moving from one island to another before the isthmus of Panama had been formed. The mother of all jararacas was small – it probably was no longer than 1 meter in length – and slightly fat. It lived crawling about the forests and had a varied diet: it ate whatever didn’t eat it before. The biologists, Marcio Martins, from the University of São  Paulo, Otávio Marques, from the Butantan Institute, and Ivan Sazima, from the State University of Campinas, arrived at these conclusions after having analyzed the size and eating habits of almost 3,000 examples of jararacas captured in all of the Brazilian states and preserved in museums both here and in the United States.

It is for not being selective that this jararaca number 1, in the vision of the São Paulo  researchers, must have colonized the most different types of vegetation – from the coastal deserts of Peru to the Amazon – and gave origin to the 40 other species of jararacas currently found in South America, 26 of them just in Brazil, where it integrated into a group of serpents that measure from 50 centimeters to almost 2 meters in length, hiding itself in all types of terrain and vegetation and that are the ones which cause the most accidents in the country.

The mother of them all left descendents similar to herself, although with different habits, presented in detail by the biologists in their book entitled, Biology of vipers. According to biologist Martins, their probable physical characteristics assimilate themselves to the two current species: the Bothrops cotiara, which live in the forests of Araucária in the south of the country, and the Bothrops fonsecai, from the high regions of the Mantiqueira and do Mar Ridge. Both are of the same size as the matriarch, but have adopted a specialized diet: only eating mammals – frogs and lizards, never again.

These two Bothrops species were not the only ones to search out their own pathway of survival and distance themselves from the origins of their lineage – not by choice, but by imposition of their environment. Changes in the São Paulo coastal landscape probably contributed to the emergence of other two species of Brazilian jararacas.

Islanders
Around 18,000 years ago the sea was more than 100 meters below its level of today and an extensive sandbar covered part of what today is the coast of São Paulo state, which was then joined with the current islands of Alcatrazes and Queimada Grande. Some time later the sea level rose and the ancient hills transformed themselves into islands. Isolated, the jararacas populations on Alcatrazes and Queimada Grande began to differentiate themselves, as attested to by the trio of biologists. Currently these snakes form species that are very different from the common jararaca, the Bothrops jararaca, which can reach up to 1.40 meters (the males do not go beyond 1 meter), living both on the ground and in the trees and feeding themselves on amphibians, lizards and centipedes when young and on rodents and other small mammals when adults. The eating habits of the species that began to emerge when the sea level rose up are also different, since rodents disappeared from these islands centuries ago.

On the 43 hectares of Queimada Grande island – and only there – lives the Bothrops insularis. The adults feed themselves exclusively on birds, which are more difficult to capture than a frog and that offers an extra risk: it can bite back. At 1 meter in length, the Queimada Grande jararaca developed more lethal venom that allows it to seize with its mouth and kill a bird before it can take any defensive action.

On Alcatrazes, less than 50 kilometers from the other, lives the Bothrops alcatraz, described in 2002 by the trio Marques, Martins and Sazima in an article in the magazine Herpetologica. This is very different. It is no more than half a meter in length and feeds itself almost exclusively on centipedes, which, for their part, gorge themselves on the cockroaches that cover the slimy ground because of the excess of guano from sea birds. “The jararaca of Alcatrazes had maintained a juvenile diet, which made it into a dwarf snake”, comments  Martins. The number 1 would have difficulty recognizing it as a member of the same lineage that arrived on the South American continent millions of years ago. Perhaps it would see it as prey and devour it.

The Project
Natural history and evolution of habitats in venomous serpents of the Bothrops genre (nº 95/09642-5); Modality: Regular Line of Research Assistance; Coordinator: Marcio Costa Martins – USP; Investment:
R$ 128,687.23

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