These giant herbivores began their evolutionary rise not long after the demise of the dinosaurs, but were abruptly driven extinct beginning around 100,000 years ago, most likely due to hunting and other pressures from our Late Pleistocene ancestors. Even recently, rhino-sized wombat-relatives called diprotodons, tank-like armored glyptodons and two-story tall sloths ruled the world. The authors note that what most conservation biologists and ecologists think of as the modern 'natural' world is very different than it was for the last 45 million years. Rowan was part of an international team of conservation biologists and ecologists from The University of Technology Sydney (UTS) in Australia, the University of Kansas and the University of California Davis and the Natural History Museum of Los Angeles County in the U.S., the University of Sussex in the U.K., the Universidad de Alcalá in Spain and Aarhus University in Denmark. So, while hippos don't perfectly replace any one extinct species, they restore parts of important ecologies across several species." "For example, the feral hippos in South America are similar in diet and body size to extinct giant llamas, while a bizarre type of extinct mammal - a notoungulate - shares with hippos large size and semiaquatic habitats. "While we found that some introduced herbivores are perfect ecological matches for extinct ones, in others cases the introduced species represents a mix of traits seen in extinct species," says study co-author John Rowan, Darwin Fellow in organismic and evolutionary biology at the University of Massachusetts Amherst. While human impacts have caused the extinction of several large mammals over the last 100,000 years, humans have since introduced numerous species, inadvertently rewilding many parts of the world such as South America, where giant llamas once roamed, and North America, where the flat-headed peccary could once be found from New York to California. Through a worldwide analysis comparing the ecological traits of introduced herbivores like Escobar's hippos to those of the past, they reveal that such introductions restore many important traits that have been lost for thousands of years. Scientists and the public alike have viewed Escobar's hippos as invasive pests that by no rights should run wild on the South American continent.Ī new study published in Proceedings of the National Academy of Sciences by an international group of researchers challenges this view. Since then, their numbers have grown to an estimated 80-100, and the giant herbivores have made their way into the country's rivers. When cocaine kingpin Pablo Escobar was shot dead in 1993, the four hippos he brought to his private zoo in Colombia were left behind in a pond on his ranch.
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