Grass The main component of the Yukagir's final meal was grass, including these stems from the Poaceae family. Remarkably, like many of the dung's floral remains, the stems have retained their color and shape ever since the mammoth tore them from the tundra roughly 22,500 years ago. (Radiocarbon dating supplied his estimated age.) Earlier studies had shown that grasses, sedges, and rushes comprised the bulk of the diet of Siberian woolly mammoths during the Pleistocene ice ages, so this discovery came as no surprise. But this was only the most obvious finding.