ICE AGE | Ice Age Giants:

Ireland's Woolly Mammoths

Back in July, we encountered one of the most famous Irish myths, which told of an ancient time when giants strode across the Irish landscape, their mighty deeds gifting Ireland incredible features like the Giant's Causeway. However, in Ireland's past there truly was a time when giants roamed through its ancient provinces, their bearing and dimensions, if anything, far more impressive than those of any mythic character. These spectacularly-tusked behemoths have become a veritable byword for immense size, and the characteristic thick, shaggy coat cladding their massive frames is what gives them their common name – the woolly mammoth.

The woolly mammoth, or Mammuthus primigenius, was a massive mammal which, with an average weight of over six tonnes and a shoulder height of almost 3.2 metres for males, was about the same size as the largest mammal on land today, the African elephant (Loxodonta africana), males of which weigh, on average, around 6 tonnes and have 3.3-metre-high shoulders. Given that the largest male African elephant bulls can be far larger than the average, with the biggest specimen on record weighing almost ten-and-a-half tonnes, the greatest woolly mammoth bulls to stomp through ancient Ireland's frozen wilds must have been monstrous beasts altogether, and, certainly, the largest woolly mammoth specimens which have been found are thought to have been more than eight tonnes in weight.

During the last glaciation of the Ice Age, which lasted from around 120,000 to 11,700 years ago, there is ample evidence of the presence of these colossal beasts in Ireland, most found in southern caves dating from a period between around 40,000 and 24,000 years ago. However, the oldest evidence of woolly mammoths in Ireland comes from the opposite end of the island, incidentally, as it happens, from the same county as the Giant's Causeway – Co. Antrim.

Here, at a site called Aghnadarragh, located close to the eastern edge of Lough Neagh, abundant remains of woolly mammoth have been found, as well as rarer remains of another cold-adapted mammal which still plies its trade in the frozen northern lands of our modern world – the musk ox.

The remains of these ancient woolly mammoths are thought to date from sometime between around 110,000 and 70,000 years ago, and it is thought that they, like other mammals at this time, first entered Ireland from Britain via landbridges, or at least by almost adjoining peninsulas or islands separated by short stretches of water (like modern elephants, mammoths seem to have been well able to swim). Although a northern corridor between Scotland and the north of Ireland has been suggested in the past, more recently experts have favoured a connection extending from the Bristol Channel to southern Ireland.

There were a number of windows when conditions were suitable for such landbridges to exist, the earliest two situated around 115,000–108,000 years ago and 90,000–84,000 years ago, respectively, when sea levels were about 50 metres lower than they are today. However, it may have been a later window, sometime around 70,000 years ago, that proved the most suitable for a crossing, sea levels at this time having plunged even further, sitting around 100 metres lower than those of our modern world.

The remains of the Antrim mammoths themselves may lend support to this idea of a later crossing as they indicate that these individuals were relatively small – well, for mammoths anyway. The pollen found alongside the mammoths suggests a climate that was cold and wet, conditions which were not ideal for plant growth, and so the poor productivity of Ireland's landscape at this time may have inhibited the growth of these early mammoths. Such conditions seem to correspond better with the window around 70,000 years ago, as Ireland's climate is known to have become more severe at this time.

Fortunately, later mammoths found in the south of Ireland are much more securely dated, as the age of their remains falls within the maximum range of radiocarbon dating, which is effective for determining dates up to around 50,000 years ago. The two earliest dates come from remains found in the fossil-rich Castlepook Cave – which sits on a limestone plateau north of the Blackwater River, near Doneraile at the foot of the Ballyhoura Hills in Co. Cork – and both fall somewhere between 39,000 and 38,000 years ago.

These mammoths appear to be part of an extensive colonisation of Ireland which is evident from around 45,000 years ago onwards. Remains of other mammals from Castlepook Cave, along with those from Shandon Cave and Ballynamintra Cave, near Dungarvan in Co. Waterford, show that mammoths were joined as pioneers in this colonisation by a stellar cast of creatures including reindeer, spotted hyenas, brown bears, and possibly giant Irish deer, while arctic fox, arctic hare, wolves, and stoats may also have been present.

During this pioneering colonisation phase, Ireland was much colder than it is today and the landscape was probably virtually treeless and dominated by hardy plants like grasses, sedges, mosses, and ferns. However, as time wore on there is some evidence for a slight upturn in temperatures, the presence of red deer and horses at Shandon and Ballynamintra caves in Waterford, centred around 32,000–31,000 years ago, suggesting that patches of woodland may have sprouted on the open grassy plains at this time.

However, by 29,000 years ago, Ireland was once more spiralling into a deep freeze, and from this time on it was no land for such temperate mammals, leaving only cold climate specialists such as the woolly mammoths and a few others to cling on to what must have been an increasingly bleak existence. From around 35,000 years ago onwards, a great ice sheet extending from northern Britain had undertaken an unstoppable advance southwards across Ireland, and by about 24,000 years ago the land had been consumed by ice.

Even the woolly mammoths, with their cold climate adaptations which included a kind of antifreeze blood and their long, powerfully insulating woolly coat (which was actually underlain by another short, dense layer), could not protect them from such remorseless forces. In Castlepook Cave, the latest dated specimen of woolly mammoth comes from around 24,600 years ago, and this individual must have been among the last mammal holdouts in Ireland, along with arctic fox and arctic lemming from the cave which date from around the same time.

Although the ice would eventually release its grip on the land and woolly mammoths would return to northern Europe, there is no evidence that they ever returned to Ireland. Thus disappeared these great Ice Age giants from the Irish landscape. Although thousands of years later giants would once more rise to dominate ancient Ireland, their lives would be lived entirely in the realms of the human imagination.