Tag Archives: south america

Giant Crocodylians Dominated South America’s Miocene Food Chain, Study Finds

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South America was home to a formidable collection of predators more than 10 million years ago, when a vast lake covered much of the continent and supported giant turtles, crocodylians and an extraordinary range of prey.

New research suggests that crocodylians, rather than mammals or other land-based predators, were the most important predators in these ancient ecosystems, particularly when it came to hunting large animals.

The findings are based on an analysis of fossil remains dating from about 10.5 million to 16 million years ago. Researchers examined bite and tooth marks preserved on herbivore fossils, providing direct evidence of interactions between predators and their prey.

A Seven-Metre Predator at the Top

The Miocene lake system supported an abundance of large herbivores, including giant ground sloths, glyptodonts — ancient relatives of modern armadillos — and several groups of large hoofed mammals.

Some of these animals, including astrapotheres and toxodontids, could weigh more than a tonne.

They shared the ecosystem with an equally imposing group of predators. Among the most formidable was Purussaurus neivensis, a giant crocodylian related to modern caimans. It could reach about seven metres in length and weigh as much as 1,800 kilograms.

Other predators included anacondas, saber-toothed mammals, flightless terror birds and sebecids, which were terrestrial relatives of modern crocodylians.

Despite this diversity, the study indicates that crocodylians were particularly important predators in the ancient ecosystem.

Fossil Bite Marks Tell the Story

Researchers from the University of Helsinki studied bite and tooth marks preserved on fossilized remains of herbivores. Such marks can reveal which predators attacked or scavenged animals, even when the predator itself is not preserved alongside its potential prey.

The frequency and characteristics of marks attributed to Purussaurus suggest that the giant crocodylian played a major role in the tropical food web.

Oscar Wilson, a postdoctoral researcher at the University of Helsinki, said the abundance of prey was so great that mammalian predators alone would not have been capable of consuming it all.

The evidence indicates that crocodylians filled an important ecological role, particularly by targeting large-bodied prey.

The findings also raise the possibility that Purussaurus influenced herbivore populations. As one of the largest predators in the ecosystem, the giant crocodylian may have exerted substantial pressure on large herbivores and helped shape the structure of the ancient food web.

The study provides a glimpse into an ecosystem where enormous predators and prey lived alongside one another — and where giant crocodylians may have occupied a position closer to the top of the food chain than previously recognized.

 

Also Read:

Crocodiles Set to Face Extinction, Says Australian Researcher

‘Nagatitan’: Southeast Asia’s biggest long-necked dinosaur discovered

 

NASA Data Detects Huge Drop in Global Fires, Good or Bad?

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NASA satellites have detected from space that the number of fires across tropical forests in South America, the Eurasian Steppe, and the savannas of Africa are increasingly declining due to settled lifestyle than previous nomadic lifestyle in the regions.

The transition is leading intensified agriculture and steep drop in the use of fire leading to decline of forest fires, said researchers from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The total acreage burned by fires declined annually by 24% from 1998 to 2015, said a research paper based on NASA satellite data and ground-based socioeconomic information. The beneficiaries are mainly the savannas and grasslands, which witnessed fires burning out half the size of the US every year, said Niels Andela, a research scientist at Goddard and lead author.

In traditional savanna cultures, people often set fires to keep grazing lands productive and free of shrubs. Since many of these communities have shifted to cultivate more permanent fields and to build more houses, roads and villages, the use of fire declines.eading organisaed governance that controls fires. By 2015, savanna fires in Africa had declined by 270,000 square miles (700,000 square km), almost equivalent to an area the size of Texas.

“When land use intensifies on savannas, fire is used less and less as a tool. As soon as people invest in houses, crops and livestock, they don’t want these fires close by anymore. The way of doing agriculture changes, the practices change, and fire slowly disappears from the grassland landscape,” said Andela.

Fires in the savanna, like this one in South Africa, burn quickly through grasses, and help prevent trees and larger shrubs from taking root. CREDIT: Guido van der Werf / Vrije Universiteit Amsterdam, the Netherlands

For their study, researchers used data derived from the Moderate Resolution Imaging Spectrometer (MODIS) instruments on NASA’s Terra and Aqua satellites, as well as other sources and compared it with trends in population, agriculture, livestock density and gross domestic product.

The scientists found a different pattern emerging in the rainforests close to the equator. Natural fires are rare in tropical forests, but as people settle an area they often burn to clear land for cropland and pastures. Once settled, they set fewer fires and the burned area declines.

The impact of a warming and drying climate is seen at higher latitudes in Canada and the American west, where fire has increased. Even in parts of China, India, Brazil and southern Africa, an increase in burned area is coming to light, said Doug Morton, a research scientist at Goddard and a co-author of the study.

“Climate change has increased fire risk in many regions, but satellite burned area data show that human activity has effectively counterbalanced that climate risk, especially across the global tropics,” Morton said.

The 24% decline in burned area may have contributed about 7% to the ability of global vegetation to absorb the increase in carbon dioxide emissions from burning fossil fuels and land use change.