Although woolly mammoths have not walked the Earth for several thousand years, they played a crucial role in the balance of the world’s prehistoric ecosystem and have become the poster animal for anyone trying to understand long-term environmental change. Now a novel chemical analysis is shedding new light on their behaviour and resolving questions that have vexed scientists for decades.
Rachel Schwartz-Narbonne studies the diet of woolly mammoths by analyzing collagen preserved on the frozen bones of these extinct animals. Photo credit: Fred Longstaffe
The “mammoth conundrum,” as it has been dubbed, revolves around what these ancient creatures ate. Like their modern elephant counterparts, they should have been restricted to a diet of plants, but their bones reveal levels of nitrogen-15 (15N) that would be associated with a carnivorous species. According to Rachel Schwartz-Narbonne, a doctoral student at Western University’s Department of Earth Sciences, accounting for this distinction can reveal a great deal about the kind of environment that set the stage for the natural world we know today. “The woolly mammoth, steppe bison and Pleistocene horse ranged from Spain to the Yukon continuously,” Schwartz-Narbonne says. “That’s a scale of ecosystem that doesn’t even make sense anymore. And then they go extinct over a period of a few thousand years. The woolly mammoth is the key to understanding the whole thing.”
Although her background is in chemistry, Schwartz-Narbonne became intrigued by the mammoth conundrum. She saw the possibility of tackling this challenge through breaking apart bulk collagen, which is a form of protein preserved in mammoth bones. While such proteins break down under normal circumstances, they are often preserved in frozen Arctic soil.
By separating these proteins into individual amino acids, she and colleagues Fred Longstaffe, Jessica Metcalfe and Grant Zazula have been able to identify other sources of 15N in the mammoth diet. In a paper published in Nature Scientific Reports, they point to dry conditions as one factor that would have increased these levels in the plants the animals were eating. Similarly, if they were foraging under the snow for food, the decaying plant matter would also have much higher concentrations of nitrogen.
For her part, Schwartz-Narbonne is eager to continue her own foraging through the mammoth bones in order to address even larger questions. “There’s just so much information in them,” she says, pointing to the extinction of the woolly mammoth as an indication of major climatic changes that irrevocably altered its diet.