August 2, 2016
Lack of fresh water killed the last mammoths, study finds
While most of the world’s wooly mammoth population died out by approximately 10,500 years ago, one group managed to survive for another 5,000 years before climate change finally caused their water supply to dry up, according to the authors of a new study.
The research, which was led by Pennsylvania State University professor Dr. Russell Graham and published in this week’s edition of the journal Proceedings of the National Academy of Sciences, concluded that a group of mammoths living on St. Paul Island in the Bering Sea outlived most of their relatives, but increasingly shallow water ultimately left them unable to quench their thirst.According to BBC News and the Daily Mail, post-Ice Age warming of the planet caused the sea levels to rise and the mammoths’ island habitat to shrink in size. Furthermore, some of the freshwater lakes that they used to keep hydrated were flooded by saltwater from the ocean, leading to increased competition for the few remaining watering holes. The increasing number of mammoths using these lakes ultimately made them unusable as well, Dr. Graham said.
“As the other lakes dried up, the animals congregated around the water holes. They were milling around, which would destroy the vegetation – we see this with modern elephants,” he explained to BBC News. “And this allows for the erosion of sediments to go into the lake, which is creating less and less fresh water. The mammoths were contributing to their own demise.”
Research said to be relevant to modern-day island populations
Dr. Graham and his colleagues reached this conclusion after analyzing the remains of 14 wooly mammoths using radiocarbon dating, and collecting sediments from underneath the lake floor in order to study their contents in order to determine what the lake environment was like at various points throughout history.
The researchers concluded these mammoths outlived their mainland cousins by about 5,000 years, becoming trapped on the island after a land bridged wound up being submerged by rising sea levels. There, they managed to survive until conditions worsened, and the influx of saltwater combined with the lack of freshwater from melting snow or rain caused their sources of drinking water to become increasingly limited.
“We do know modern elephants require between 70 and 200 liters of water daily,” Dr. Graham told BBC News. “We assume mammoths did the same thing. It wouldn't have taken long if the water hole had dried up. If it had only dried up for a month, it could have been fatal.”
University of Wisconsin-Madison geography professor John “Jack” Williams, who was part of the research team, said that the discovery was relevant to modern-day islands and the people and animals currently living in those locations. As such, he and his colleagues hope to create a model of the conditions at St. Paul Island during the time it was inhabited by mammoths.
“It’s a cool story in multiple ways. I can’t think of any other case where freshwater availability was the driver of extinction,” Williams, who also serves as director of the UW–Madison Nelson Institute’s Center for Climatic Research, said in a statement. “We want to model the island as it was when the mammoths existed on it. We want to learn the carrying capacity of the island, their population numbers, their dietary and water requirements.”
Image credit: Wikimedia Commons