Dwarfed Giants: Woolly Mammoths on Wrangel Island

Fig 1: Vartanyan et al (1993) Map of Wrangel Island

On the reading list for lecture 2 is an interesting (and conveniently, very short!) article by Vartanyan et al (1993) on Holocene dwarf mammoths on Wrangel Island, which survived long past the consensus extinction date of around 12,000 radiocarbon years BP of the ‘normal’ mammoth. Numerous sets of fossilized teeth 30% smaller than normal mammoth teeth have been found on Wrangel Island, and were dated as young as 7,000 – 4,000 radiocarbon years BP. Based on the relationship between tooth and body size, researchers have concluded that the dwarf mammoth was 180-230cm in shoulder height, at least 30% smaller than woolly mammoths on the mainland. 

Wrangel Island provided an isolated refugia for the mammoth in its dwarf form. In the late Pleistocene, Wrangel Island was part of the land of Beringida, joined up with the lowlands of East Siberia, Alaska and the present-day Arctic shelf. By 12,000 radiocarbon yeas BP, Wrangel Island was separated from the mainland, separating the local population of mammoth from the mainland population. This Arctic island had a much higher diversity of plant types and open vegetation, which supported mammoth populations. Even in the present day, the vegetation on this island is considered to be a poorer relic of late Pleistocene grassland.  Nevertheless, the dwarfing of mammoth size is an adaptation which reflected the severity of the stress that the original ‘normal’ mammoths faced in their original habitat. 

Fig 2: Stuart (2005) Timeline of Mammoth Extinctions in Different Regions

The significance of the Wrangel Island dwarf mammoths is that they provide a better understanding of how megafauna extinction took place, and the role of refugia. Extinction is not a one-off event in which animals are quickly wiped out, but rather, a gradual shrinking of range as these they increasingly found their environments unsuitable. Fig. 2 (above) illustrates the staggered extinction of mammoths, with some populations making their ‘last stands’ in certain places. A useful complementary article to read is Stuart’s(2005) more recent paper on new evidence of mammoths surviving much later than previously thought in other places that provided similar refugia, such as the new mammoth molars found in Estonia, which date to 10,000 radiocarbon years BP. Another example is the continued existence of woolly mammoth in the far north of Siberia, the Taymyr Peninsula, for another 2,000 radiocarbon years after most of them became extinct around the world. As the Holocene period brought warmer climates and forests rather than the open-steppe vegetation which favoured mammoths, such colder refugia allowed mammoths to survive. However, the Wrangel Island mammoths also add more mystery to the megafauna extinction debate. If climates became unsuitable, surely the mammoths were more vulnerable to change on an island, where migration was not possible, rather than on the mainland? Could it be the lack of humans on the island? Could human activities have inhibited the normal migrational responses of megafauna to climate change, thus limiting their range?

While the Wrangel Island mammoths raise even more questions on the megafauna debate than can be answered, it provides important lessons for modern conservation. Wrangel Island highlights the resilience and adaptability of natural ecosystems to change, e.g. through migration and physical adaptation (dwarfing). However, the combination of climate change and human impacts was just too much for the megafauna to bear. Today, as our ability to alter the environment is ever more profound, we need to be increasingly responsible for the consequences of our actions.

References

Vartanyan, S. L. (1993) ‘Holocene dwarf mammoths from Wrangel Island in the Siberian Arctic’, Nature 362, pp. 337-340.

Stuart, A. J. (2005) ‘The extinction of woolly mammoth (Mammuthus primigenius) and straight-tusked elephant (Palaeoloxodon antiquus) in Europe’, Quaternary International 126-128, pp. 171-177.