Preserved frozen remains of woolly mammoths, with much soft tissue remaining, have been found in the northern parts of Siberia. This is a rare occurrence, essentially requiring the animal to have been buried rapidly in liquid or semi-solids such as silt, mud and icy water which then froze. This may have occurred in a number of ways. Mammoths may have been trapped in bogs or quicksands and either died of starvation or exposure, or drowning if they sank under the surface. The evidence of undigested food in the stomach and seed pods still in the mouth of many of the specimens suggests that neither starvation nor exposure are likely. The maturity of this ingested vegetation places the time period in autumn rather than in spring when flowers would be expected.[19] The animals may have fallen through ice into small ponds or potholes, entombing them. Many are certainly known to have been killed in rivers, perhaps through being swept away by river floods. In one location, by the Berelekh River in Yakutia in Siberia, more than 9,000 bones from at least 156 individual mammoths have been found in a single spot, apparently having been swept there by the current.[20]
[19]^ E. W. Pfizenmayer was one of the scientists who recovered and studied a mammoth that was found at the river Berezovka in the early 1900s. He wrote: “Its death must have occurred very quickly after its fall, for we found half-chewed food still in its mouth, between the back teeth and on its tongue, which was in good preservation. The food consisted of leaves and grasses, some of the latter carrying seeds. We could tell from these that the mammoth must have come to its miserable end in the autumn.” See Pfizenmayer, E. W. (1939). Siberian Man and Mammoth. London: Blackie and Son.