Extension of the Irish Elk

Reviewed by: Eamon O Flynn 

Research suggests that the worldwide extinction of the mega-fauna of the Late Pleistocene epoch is attributable to ‘overkill’ by human hunters, climatic/ vegetation changes or even a combination of both. Being from Ireland, one mega-fauna species in which I am particularly interested is the Irish Elk (Melaloceros giganteus), sometimes referred to as the ‘Giant Deer’. This species survived in western Siberia until about 7,700 years ago (6,900 radiocarbon years) which is more than three millennia later than its previously accepted terminal date. Therefore, the reasons for the worldwide extinction of the Giant Deer are to be sought in Holocene not Pleistocene events. In Ireland, however, it is believed that the Irish Elk became extinct about 10,600 years ago.

  The Megaloceros giganteus, with a max shoulder height of 2.1 m and an antler span of up to 3.6 m , is one of the most striking and unique extinct animal of the Palaearctic. The Irish Elk ranged from the middle latitudes of Eurasia, from Ireland to east of Lake Baikal during the Last Cold Stage. According to its anatomy and distribution, the giant deer was a mixed feeder, having both to browse and to graze in productive environments- vital for annual antler growth in males. Alternatively, it is a possibility that the huge antlers could have excluded males from even moderately dense woodland.

 ‘Maladaptation’ was formerly one theory on the extinction of the M. giganteus but, more recently, in 1999 it was suggested that the seasonal nutrient requirements of the huge antlers seems a likely explanation also. Focusing on the well-studied Irish population of the Allerod phase (12,000 to 10,600 uncalibrated radiocarbon years B.P). Ireland has yielded most of the best specimens, including near-complete skeletons retrieved from calcareous lake sediments which are ideal for the preservation of bone. 

It is further noteworthy that the adult male Irish Elk grew the largest antlers of any extinct or extant cervid.  Irish Elk antlers weighing 40 kg at the end of velvet shedding would have contained 2.1 kg of nitrogen, 7.6 kg of calcium, and 3.8 kg of phosphorous. The nitrogen requirements for antler growth were met by forage intake. About 6 % of the calcium and 10 % of the phosphorous in the antler were reabsorbed from the skeleton because dietary intake of minerals was insufficient to meet requirements for antler mineralization. 

The mineral reabsorbed from the skeleton in summer would have to be replenished by dietary intake over the following winter- often a difficult task for the Megaloceros. This was further compromised by vegetative changes. Pollen records show a shift in plant species composition from tall-willow spruce community during the Allerod to tundra in the Younger Dryas. The reduction in forage density would have made replenishing calcium and phosphorous in the skeleton more difficult, as well as making it more difficult for male Irish Elk to replenish fat reserves depleted during the rut. Therefore, a depleted skeleton could lead to brittle bones that would be more easily broken when bulls fought during the rut. If the depletion of bone calcium and phosphorous were not replenished from the fall and winter diet before antler growth the following year, the resorption could lead to permanent osteoporosis or reduced antler growth- either of which would be likely to reduce the genetic fitness of affected individuals.

   Looking at the data, there was a striking absence of evidence of the Irish Elk during the long interval from 20-12.5 kyr- suggesting its withdrawal entirely from western and central Europe. This period corresponds broadly with the period when the Scandinavian and Alpine ice sheets expanded (the Last Glacial Maximum) leaving treeless steppe tundra vegetation. This drove the giant deer to south Eastern Europe and south central Asia, probably in areas where tree and shrub vegetation persisted. After this period ( LGM ), Megaloceros re-occupied part of north and Western Europe. This is shown by extensive re-colonization of the Isle of Man and Britan by around 12.2 kyr, and of Ireland, southern Scandinavia and northern Germany by around 12 kyr. However, there is no evidence which would support the return of the giant deer to southern or central parts of Western Europe.

 In both Ireland and the Isle of Man extinction was almost definitely due to climatic/vegetation change since human occupation of these areas wasn’t until the early Holocene epoch, around 9 kyr. In Ireland, evidence of Holocene survival is based on specimens that are somewhat doubtful. Therefore, the Younger Dryas cold episode with reduced forage density coincides with the extinction of the Irish Elk about 10,600 years before the present time.

The Irish Elk could well be considered the most elegant animal to ever have graced our lands. Its demise is to be lamented.

References

Ø  Moen, R. A., Pastor, J. &Cohen, Y. Antler growth and extinction of Irish Elk. Evolutionary Ecology Research, 1: 235-249 (1999)

Ø  A. J. Stuart, P. A. Kosintsev, T. F. G. Higham & A. M. Lister. Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth.