Wednesday, March 4, 2009

Paleontologists Strike Fossil Gold in Colombia

With excerpts from:

BOGOTA, Colombia -- Carlos Jaramillo is 39 years old but loves to dig in the dirt -- especially the dry, flaky shale formations of Colombia's Guajira province. If you talk to a paleontologist, he explained, you're talking to a kid who never grew up. For the past five years, Jaramillo and his team of paleontologists have been burrowing ground so rich in fossils that they have made the kinds of discoveries that thrill the scientific world. And they still have years of digging ahead of them at this site in the Cerrejon region of northeastern Colombia, a remote and oven-hot place not unaccustomed to drug traffickers and the occasional rebel column.

Last month, an international group of scientists revealed in the journal Nature that Jaramillo's team had made a startling discovery -- a species of snake larger than a school bus that ruled northern South America 60 million years ago. Evolving after the extinction of the dinosaurs, Titanoboa cerrejonensis -- or titanic boa from Cerrejon -- might have been the largest vertebrate living on land at that time, the Paleocene era. Indeed, it had an average length of 43 feet -- far longer than any of today's pythons or anacondas -- and it weighed 2,500 pounds, more than a small car. Its diet included giant turtles and crocodiles -- Jaramillo's team also discovered the fossilized remains of those creatures under layers and layers of dirt and shale.
In all, Jaramillo and his team have found the remains of 28 snakes that measured between 42 and 49 feet. What we have is a population of big snakes, said Jaramillo, who is Colombian. It's not one snake. It's a bunch of them.

Funded by the Smithsonian Institution, Jaramillo's team -- the other members are students working on their master's or doctorate degrees -- has been digging in the most unusual of sites, the enormous, open-pit Cerrejon coal mine. Operated by some of the world's biggest mining multinationals, Cerrejon's 270 square miles are filled with moonlike craters 300 feet deep.
Excavators and earth movers work without pause, carting off 32 million metric tons of coal a year. They also remove rock and dirt that the paleontologists would never be able to budge -- making it much easier for Jaramillo's team to reach the valuable fossils that he said are opening a window on the first tropical forests that evolved after the dinosaurs disappeared. They close a pit, and then they open up a new pit, so we always have possibilities, Jaramillo said. I think we'll have 10, 15 years to do excavations. We always find new things.

Arriving for a dig a few months ago, Jaramillo scanned the horizon. For a first-time visitor accompanying him, it appeared to be anything but ground zero for fossils. Huge trucks roared past carrying mounds of coal to be exported to Europe and the United States, and heavy machinery could be heard in the distance, kicking up clouds of dust. Wearing white work helmets, Jaramillo and two members of his team descended into one of the pits. They carried the tools of their trade -- a light chisel to brush off dirt and hand lens to examine their discoveries. Perhaps even more important is simply having a sharp eye and a soft touch. You need to train your eyes and you need to have special skills to do that, Jaramillo explained. If you don't have the skills, you will come here for a year and never find anything.

The team's work has already turned up giant crocodiles and freshwater turtles that weighed 300 pounds. There are also hundreds of fossils of leaves so perfectly preserved that the paleontologists can easily make out the veins and ridges. Oh my God, you can tell the venation very well! Jaramillo exclaimed, examining a leaf belonging to the Araceae plant family. This is 60 million years old. So it's probably one of the oldest Araceaes ever found. He then showed off the remains of a recently discovered anaconda, and then the fossils of fish and crabs, too. This was like a big delta, it was a tropical rain forest, he said. That may be hard to fathom today because it rarely rains in Guajira province, which is now mostly home to scrub grass and small trees.

Jaramillo and other scientists think the forest that once thrived in Cerrejon evolved after a giant meteorite hit Yucatan Peninsula. The fossils they are recovering are helping to explain how the forest responded to that environmental catastrophe -- and may provide clues on how the modern world will react to, say, global warming. The team's discoveries are piling up -- 4,000 fossils of plants, fruit, flowers and seeds; 75 turtles, 25 crocodiles, as well as fish, crabs and other creatures. The fossils belong to Colombia but are on loan to the Smithsonian Tropical Research Institute in Panama and at the University of Florida at Gainesville.

Still, Jaramillo searches for more. He said each find is like the chapter of a book. Pieced together, they tell a long and complex story, one that he said is not yet complete. The feeling is amazing, because we don't know if here we're going to have a fantastic flower nobody has seen for the last 60 million years, or perhaps there is nothing, he said, as he took a chisel to a mound he had recovered from the shale. So you just crack the rock open and hope for the best.

Monday, February 23, 2009

Cannibalism among rattlesnakes helps females to recover after birth

Spanish, American and Mexican researchers have produced the first quantitative description of cannibalism among female rattlesnakes Crotalus polystictus after monitoring 190 reptiles. The study has shown that these animals ingest on average 11% of their postpartum mass (in particular eggs and dead offspring) in order to recover energy for subsequent reproduction.

The lack of information about cannibalism in rattlesnakes Crotalus polystictus led researchers to start a study in 2004, which they continued for three years in central Mexico, where this species is endemic. They measured 'cannibalistic behaviour' among 190 females, which had 239 clutches of eggs, and determined that this phenomenon is justified by 'enabling the mother to recover and regain strength.'

'A cannibal rattlesnake female can recover lost energy for reproduction without having to hunt for food, a dangerous activity that requires time and expends a great deal of energy,' Estrella Mocino and Kirk Setser, lead authors of the study and researchers at the University of Granada, along with Juan Manuel Pleguezuelos, tell SINC.

The study, published in the latest issue of the journal Animal Behaviour, shows that cannibalism in this species is an evolutionary result of its feeding behaviour, since its prey is dead for some time before being eaten by the snake. 'Viperids in general are prepared to eat carrion, and for this reason it is not so strange that they consume the non-viable sections of their clutches after going through the great energy expenditure caused by reproduction,' says Mocino.

The research team say this behaviour can be explained by four biological factors - the day of the birth (females that give birth at the end of July are more likely to be cannibals, since they have less time to feed and prepare themselves to reproduce again), the proportion of dead babies per clutch, the level of maternal investment (the larger the brood, the greater the chance that it will contain non-viable elements, which she will eat), and stress caused by being in captivity (the researchers maintained the females in captivity for an average of 21 days).

Of all the females, 68% consumed part or all of their dead offspring, and 83% of these ate them all, and waited little time to do so (around 16 hours), although some ate them 'immediately after giving birth,' adds Mocino. The rest (40%) of the females 'did not display cannibalistic behaviour.'

According to the scientists, cannibalism is 'not an aberrant behaviour, and is not an attack on the progeny,' since it is not the same as parricide or infanticide as it does not involve live elements. It simply recovers some of what the snake invested in the reproduction process, and prepares it to reproduce once again.

The scientists showed there was a low risk of the snakes eating healthy offspring, which look very similar to dead ones for the first two hours after emerging from their membranes. During the study, only one female ate live babies.

'In comparison with mammals or birds, snakes are not as maternal, but the study shows that they also display behaviour that has evolved, and that helps the female and her offspring to reproduce and grow successfully,' say Mocino and Setser.

Crotalus polystictus is categorised as a 'threatened species' according to the Official Mexican Regulations on protection of native species of wild flora and fauna in Mexico. Limited habitat, urban expansion and the growth of agriculture are the main threats to the snake.

To date, the scientists have marked more than 2,000 individuals of this species, which range in length on average from 50 cm to 90 cm, and which display different survival strategies from many other rattlesnakes in the north of Mexico and the United States.

This reptile has a very rapid reproduction rate, suggesting that it is experiencing a high death rate caused by external factors. As well as contributing to scientific knowledge about animal cannibalism from an evolutionary perspective, the scientists hope that publicising these results will 'lead to human beings being less aggressive towards these snakes.'

Source: Plataforma SINC

Friday, February 6, 2009

Giant snake fossil offers clues to ancient climate(

PANAMA CITY: Scientists have found a 60-million-year-old fossil of the world's largest snake, a 13-meter, 1-ton behemoth dubbed Titanoboa, in a coal mine in Colombia, the US Smithsonian Tropical Research Institute says. "The discovery of Titanoboa challenges our understanding of past climates and environments, as well as the biological limitations on the evolution of giant snakes," said Jason Head, member of the Panama-based research institute and lead author of the study published Thursday in Nature magazine.

"This shows how much more information about the history of Earth there is to glean from a resource like the reptile-fossil record," said the assistant professor of ecology and evolutionary biology at the University of Toronto Mississauga.

From the size of the 1.14-ton Titanoboa, scientists have estimated the average annual temperature in the tropical jungle it inhabited 60 million years ago at 30-34 degrees Celsius.

"This temperature estimate is much hotter than modern temperatures in tropical rainforests anywhere in the world," said Carlos Jaramillo, Smithsonian staff scientist and co-organizer of the excavations in Colombia.

"That means tropical rainforests could exist at temperatures 3-4 degrees Celsius hotter than modern tropical rainforests experience," he added, alluding to theories that would have tropical forests disappear if global warming boosts temperatures by that measure in the future.

The size and weight of Titanoboa - its name is derived from its current descendant, the boa constrictor - was determined by comparing its fossil vertebrae to the radius-to-length ratio of living snakes.

The previous snake size record was held by a python that measured 10 meters, the Smithsonian said.

The latest fossils were found inside the Cerrejon coal mine, in Colombia's northeastern region of Guajira. - AFP