Comparative analysis of the mammoth populations on Wrangel Island and the Channel Islands

At the end of the Pleistocene the range of distribution of the woolly mammoth (Mammuthus primigenius) appreciably moved to the extreme northern portions of Eurasia. At the boundary of the Late Pleistocene and early Holocene the distribution was divided into isolate groups. In the early Holocene the last mammoth populations were present on the Taimyr Peninsula and on Wrangel Island, in the Siberian Arctic Ocean. In the latter location, mammoths survived to the middle Holocene (3,000-4,000 years ago). In Northern America the range of distribution of the Columbian mammoth (Mammuthus columbii) also changed appreciably ate the end of the Pleistocene, producing separate, isolated populations. One of these isolate groups was established on the Californian Channel Islands. Comparisons of the morphological features of dentition and skeleton were made, to reflect the adaptations to habitation in the separate environments. The Holocene Wrangel Island molars have a narrow crown and a frequency of enamel plates slightly exceeding late Pleistocene Siberian mammoths. On the Channel Islands the lamellar frequency increased 20% for M. exilis. By comparison of parameters of the bones it is apparent that the American mammoth generally had a smaller size, although some individual bones are quite comparable. Our conclusions indicate that the Channel Islands mammoths are dwarfed, whereas the Wrangel mammoths are no longer considered to be dwarfs. It is probable that the major difference between the two populations is the length of isolation. For Wrangel Island it was not more than 6,000-7,000 years. Also, during the winters, Wrangel Island was connected to the mainland by ice, allowing migration in both directions. For the Channel Islands the time of isolation is not fully known, but it apparently exceeds 40,000 years. It is possible that additional migration of M. columbi from the mainland took place, but no dwarf mammoths have been discovered on the Californian coast. On the Channel Islands selective forces acted towards smaller animals, resulting in a new species (M. exilis) with 150-180 cm shoulder height. Holocene mammoths from Wrangel Island ranged from 180-230 cm shoulder height and probably corresponded to the last Late Pleistocene populations in northern Siberia.