The giant Irish elk, Megaloceros giganteus, cut an impressive and imposing figure with its massive antlers; at up to four metres across the largest in any form of deer known.
The species was thought to have died out in the Late Pleistocene, during a period of glaciation about 10,600 years ago. New radiocarbon dating research has changed this view, however, and it now seems the elk survived for at least another 1,400 years. Details of the research by scientists from Liverpool's John Moores University, the National Museums of Scotland and University College London are published in the current issue of Nature.
The Irish elk, actually a form of deer, was about the size of a modern moose, but had a remarkable set of antlers, which weighted up to 40kg. Most remains date from between 12,000 years and 11,000 years ago, but the bones of a near-complete skeleton of an adult male found in 1819 at Ballaugh in the Isle of Mann were found to date from 9,430 BC, making him the "youngest" giant elk recovered anywhere in the world.
The date is of importance to scientists because it changes the range of possibilities behind the Irish elk's extinction. The older dates fitted nicely into an assumption that a short period of increased glaciation reduced the availability of forage and so did for the elk.
Scientists believe the antlers were a key component in attracting females and so were "selected", in an evolutionary sense, by generations of elk, leading to their remarkable size. Growing them put huge nutritional demands on the elk, however, and when their food supply was disturbed at the PleistoceneHolocene boundary 10,000 years ago, this put the animals under stress.
The research team took detailed measurements of all components of the skeletal remains. The bones "show that sexual selection maintained a relatively large antler size until the last documented survival of the species", the team writes.
The animals were caught in an evolutionary trap, however, as food supplies dwindled. Their preferred selection criteria were size, but food sources couldn't keep up and so guarantee attractive antlers. "Based on the latest data, reported extinction is explained in terms of the reduced forage density during that episode, leading to a conflict between sexual selection for increased body and antler size, and nutritional selection pressures for reducing them."
These factors probably reduced populations and possibly the body size of M. giganteus, "but our dating indicates that they cannot have caused its extinction", the authors said.
They speculate that ancient hunters foraging in the temperate forests of north-west Europe could have brought about the elk's final demise. They point out, however, that the age for the youngest elk predates the earliest evidence of human hunters in either the Isle of Man or Ireland.
"Our new dates for Megaloceros add an important new species to the list of Holocene survivors from the Pleistocene world," the authors conclude. They mention another unexpected Holocene survivor, the woolly mammoth, following the discovery of dated remains on Wrangel Island in the Siberian Arctic.
"It is possible that we are witnessing a pattern of terminal survival of Pleistocene mega-fauna on islands at the margins of continents", the authors conclude.
