The Irish Elk, the World's Biggest Deer

An Irish Elk stands in deep grass on a foggy hillside.
Daniel Eskridge/Stocktrek Images/ Stocktrek Images/ Getty Images

Although Megaloceros is commonly known as the Irish Elk, it's important to understand that this genus comprised nine separate species, only one of which (Megaloceros giganteus) reached true elk-like proportions. Also, the name Irish Elk is something of a double misnomer. First, Megaloceros had more in common with modern deer than American or European Elks, and, second, it didn't live exclusively in Ireland, enjoying a distribution across the expanse of Pleistocene Europe. (Other, smaller Megaloceros species ranged as far afield as China and Japan.)  

The Irish Elk, M. giganteus, was far and away the largest deer that ever lived, measuring about eight feet long from head to tail and weighing in the neighborhood of 500 to 1,500 pounds. What really set this megafauna mammal apart from its fellow ungulates, though, were its enormous, ramifying, ornate antlers, which spanned almost 12 feet from tip to tip and weighed just short of 100 pounds. As with all such structures in the animal kingdom, these antlers were strictly a sexually selected characteristic; males with more ornate appendages were more successful in intra-herd combat, and thus more attractive to females during mating season. Why didn't these top-heavy antlers cause Irish Elk males to tip over? Presumably, they also had exceptionally strong necks, not to mention a finely tuned sense of balance.

The Extinction of the Irish Elk

Why did the Irish Elk go extinct shortly after the last Ice Age, on the cusp of the modern era, 10,000 years ago? Well, this may have been an object lesson in sexual selection run amok: It's possible that dominant Irish Elk males were so successful and so long-lived that they crowded other, less-well-endowed males out of the gene pool, the result being excessive inbreeding. An overly inbred Irish Elk population would be unusually susceptible to disease or environmental change--say, if an accustomed source of food disappeared--and prone to sudden extinction. By the same token, if early human hunters targeted alpha males (perhaps wishing to use their horns as ornaments or "magic" totems), that, too, would have had a disastrous effect on the Irish Elk's prospects for survival.

Because it went extinct so recently, the Irish Elk is a candidate species for de-extinction. What this would mean, in practice, is harvesting remnants of Megaloceros DNA from preserved soft tissues, comparing these with the gene sequences of still-extant relatives (perhaps the much, much smaller Fallow Deer or Red Deer), and then breeding the Irish Elk back into existence via a combination of gene manipulation, in-vitro fertilization, and surrogate pregnancy. It all sounds easy when you read it, but each of these steps poses significant technical challenges--so you shouldn't expect to see an Irish Elk at your local zoo anytime soon!


Irish Elk; also known as Megaloceros giganteus (Greek for "giant horn"); pronounced meg-ah-LAH-seh-russ


Plains of Eurasia

Historical Epoch:

Pleistocene-Modern (two million-10,000 years ago)

Size and Weight:

Up to eight feet long and 1,500 pounds



Distinguishing Characteristics:

Large size; large, ornate horns on head

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Strauss, Bob. "The Irish Elk, the World's Biggest Deer." ThoughtCo, Sep. 23, 2021, Strauss, Bob. (2021, September 23). The Irish Elk, the World's Biggest Deer. Retrieved from Strauss, Bob. "The Irish Elk, the World's Biggest Deer." ThoughtCo. (accessed December 2, 2022).