MAMMAL NAMES | Reality Is Not What It Seems:

The Revealing Names & Surprising Evolutionary Relationships of Ireland's Deer

The truth of the evolutionary relationships between Ireland's deer can fracture our sense of reality, warning us not to make assumptions based solely on what we see

For many months now our eyes have been fixed on the seas surrounding Ireland, taking a long, deep gaze at those masters of the deep, the whales. However, this month we will return to the land once more to meet a group of hoofed herbivores that are amongst the whales’ closest living relatives – the deer. Like their fascinating aquatic kin, the deer inhabiting Ireland possess many interesting names which can serve to, in a way, endow us with x-ray vision, allowing us to see beyond mere outward appearance to the truth that lies beneath, unveiling the reality of their surprising evolutionary relationships.


The deer are one of the best-represented mammal groups in Ireland, with five species now known to inhabit the island, and they come in a variety of different forms, from mighty to minnow. The largest of these are the two native species, the red deer and fallow deer, while the three non-native species, the sika deer, roe deer, and muntjac deer, are all significantly smaller in size. We can begin by looking at the first two, as they are not only the largest forms, but the longest inhabitants of Ireland.


The red deer are by quite a distance the species with the most ancient roots in Ireland, with evidence of their presence during the Holocene Epoch (c. 11,700 years ago–Present) stretching back almost 5,000 years. Also, they are easily the largest, with red deer stags being impressive, powerful beasts that stand 1.2–1.4 metres high at the shoulder and reach 200 kilograms in weight, allowing them to claim not only the title of 'Ireland's largest deer', but of 'Ireland's largest native mammal'.

The red deer can claim the title of 'Ireland's largest native mammal'

It seems appropriate, then, that the red deer’s scientific name, Cervus elaphus, derives partly from a word for ‘stag’, with cervus meaning ‘stag’ in Latin. Indeed, cervus constitutes an element in the names of all the deer in Ireland, as the family name for the deer as a whole, Cervidae, is also derived from this term. Getting back to the red deer, the species name, elaphus, is more general in nature, being the Latinised form of the Greek elaphos, simply meaning ‘deer’.


The Irish name, fia rua, means the very same as the English name, ‘red deer’, although in both instances this name does not fully encompass the colour of this species. Although the name derives from the fact that during the summer this deer most commonly sports a reddish brown coat, the colour can actually vary from dark brown to beige, while in the winter the coat colour ranges from brown to greyish.


As it happens, Ireland’s other native, and next-largest species, the fallow deer, also has names which derive from its colour. This deer owes its common name, ‘fallow’, to a word in Old English, fealu, meaning ‘yellowish brown’, while its Irish name, fia buí, translates as ‘yellow deer’. As with the red deer, though, these names do not fully convey the true colour range of the coat in this species, which is even wider, varying from a yellowish white to almost black.

As this picture shows, fallow deer are not always as yellow as some of their names suggest

Also like the red deer, at least in part, the scientific name of the fallow deer, Dama dama, derives from a general word for ‘deer’, in this case dama being the broad term for ‘deer’ in Latin. However, the names of Ireland’s two native species are also markedly different in some respects, one of the most notable being that whereas red deer males are referred to as stags, females as hinds, and young as calves, in fallow deer the respective names are buck, doe, and fawn.


The fallow deer can also claim to have more titles for their males at different ages, as stated by Hayden & Harrington: ‘There is an extensive vocabulary of terms related to fallow deer; for example, male fallow deer in their first six years of life are respectively referred to as fawns, prickets, sorels, soars, bare bucks/bucks of the first head, and great bucks.’ And these bucks do indeed deserve to be called great, as they are quite large, standing around a metre tall at the shoulder and weighing about 100 kilograms.


Such dimensions may make fallow deer quite a bit smaller than red deer, but they are still noticeably larger than the third largest deer species in Ireland, the sika deer. Although the largest sika deer stags may stand at a comparable height to fallow deer, they are much lighter, weighing only around 50–60 kilograms.


The sika deer are also far more recent arrivals in Ireland than fallow deer. By the time sika deer were first brought to the island in the mid-nineteenth century, when the introduction of exotic species to enrich local faunas was in vogue among aristocrats, fallow deer had already lived alongside their large neighbours the red deer for around six centuries, having been introduced to Ireland by the Normans in the mid-thirteenth century.


But though the fallow deer in Ireland can claim a long association with Ireland’s red deer in terms of co-existence on the island, as well as a closer similarity in size, the island’s sika deer possess a far deeper connection to them, which becomes immediately obvious when we hear their scientific name, Cervus nippon. Sika deer, then, belong to the same genus as red deer, and so share a more recent common ancestor with them than do the fallow deer.

Sika deer belong to the same genus, Cervus, as red deer

Indeed, when we look past differences in size, it is clear that the sika deer are more similar to red deer than the fallow deer are in some very obvious ways. Perhaps the most noticeable of these is the antlers, with both the red deer and sika deer possessing multi-pronged antlers that crown their heads like little trees unleafed by winter. The fallow deer, on the other hand, have antlers of a far different design known as palmate, where the spaces between the individual prongs, or tines, are filled in to some degree, giving the antler a much rounder appearance, more like that of a moose.


In fact, recent evidence has shown that the fallow deer may be even more distantly related to the red deer than traditionally thought, occupying not just a different genus to them but a different tribe. As we saw back in May 2016, recent genetic studies have bolstered a view suggested by multiple lines of evidence that Ireland’s modern fallow deer are the closest relatives of that great cervid colossus with enormous palmate antlers that reigned supreme in the wilds of Ice Age Ireland – the giant Irish deer. If this is true, as the evidence increasingly indicates it to be, then the fallow deer belong not to the tribe Cervini, as the red deer do, but are the last representatives on Earth of a tribe of medium-to-giant-sized deer, the Megacerini, and their ancestors may have been far larger than they are today.

A reduction in size also appears to have occurred in the evolutionary descent of the sika deer, which explains why they are now so much smaller than their relatives the red deer, and, in fact, where this occurred links us neatly to the roots of their common, scientific, and Irish names.


Sika deer are thought to have evolved their small size due to their ancestors’ colonisation of the smaller islands of Japan. A change in size due to island colonisation is a common occurrence in evolution and is known as the island rule: mammals which become isolated on islands evolve faster and quickly change in size; large mammals, deprived of plentiful food sources such as vast grasslands, evolve into small-scale versions of their mainland counterparts, while small mammals, in the absence of many of their natural predators and competitors, get bigger.


This, then, appears to be how the sika deer diminished in size, and Japan and nearby areas of East Asia are still the native lands of sika deer today. So, it is unsurprising that the common name ‘sika’ comes from the Japanese word for ‘deer’, while the species name, nippon, comes from the Japanese word for ‘Japan’. In turn, the Irish name, fia seapánach, simply means ‘the Japanese deer’.


As small as Ireland’s sika deer are compared to their red deer relatives, though, they are still heavyweights when put beside the last two deer species inhabiting Ireland today. These are two very recent arrivals on the island, the Chinese muntjac, whose presence was first confirmed in 2007, and the roe deer, which first appeared in 2011 (although roe deer were briefly introduced to the grounds of Lissadell House in Co. Sligo from 1870 to the early 1900s when they were obliterated through hunting).


Both of these newcomers have names which refer to their diminutive size, the scientific name of the roe deer, Capreolus capreolus, appearing to derive from the Latin capra, meaning ‘goat’, making capreolus ‘small goat’. In turn, the common name of the muntjac derives from the Dutch muntjak, which itself comes from mencek, a word from the Sundanese language of western Java in Indonesia, which, according to the Oxford English Dictionary, means ‘small deer/roe’.

The scientific name of the roe deer, Capreolus, means 'small goat'

This is also, of course, the source of the genus part of its scientific name, Muntiacus reevesi, while the species name commemorates John Reeves, a nineteenth century English naturalist who worked for the British East India company. This also explains why an alternative common name for the Chinese muntjac is Reeve’s muntjac.


Of the two, it seems the roe deer is the larger, with a shoulder height that can reach around 90 centimetres and an upper weight of about 23 kilograms or more, while the Chinese muntjac only reaches about 50 centimetres in shoulder height and has an upper weight of just 18 kilograms.


The roe deer is also closer to some of the larger deer in terms of its names, as, like the red deer and fallow deer, some of them derive from the colour of its coat. ‘Roe’ itself is thought to come from the Old English ra, which itself may ultimately derive from a proto-Indo-European root, rei, meaning ‘streaked, spotted, striped in various colors’, although this does not seem to be a particularly accurate description of its coat, except for the young, which are indeed spotted.


In this case, then, the Irish name, fia odhar, may be more apt, with odhar meaning ‘dun’ (dull greyish brown) or ‘dull/dark’, corresponding more closely to a coat that is reddish brown in the summer and a darker grey brown in the winter. In fact, the reddish brown colour of the roe deer's summer coat sometimes results in individuals being misidentified as red deer.


It is not only in terms of size, names, and colour that the roe deer is more similar to the three larger deer in Ireland than is the Chinese muntjac, though, as this latter form is truly the odd-one-out on the island when it comes to its antlers and teeth. Whereas the roe deer has relatively small antlers compared to the larger three, they are still branched, and its overall general appearance is quite similar. Conversely, the Chinese muntjac sports very short antlers that are just single spikes, while it differs completely from the other four in that the males also possess upper canines that are elongated into little tusks that project very visibly from the mouth when closed, like the fangs of a cartoon vampire.

The 'odd-one-out' amongst Ireland's deer, the Chinese muntjac, has short, single-spiked antlers and fang-like tusks

With the Chinese muntjac being such an oddball compared to the others inhabiting Ireland, it would seem reasonable to assume that it must be the most distantly related, but this is, surprisingly, not the case. In fact, it is the roe deer that is the undisputed outlier in terms of evolutionary relationships.


Whereas the Chinese muntjac belongs to a different tribe than the red deer, sika deer, and fallow deer, being a member of Muntiacini, it lines up beside them in the evolutionary divide in the deer family, all four belonging to the subfamily Cervinae. Although the muntjac’s strange, short-antlered, long-canined form may appear to be a retention of primitive features, as all deer ultimately evolved from such a form, it is possible that it actually re-evolved such a form from a longer-antlered, shorter-canined ancestor that would have borne a closer resemblance to the other members of its subfamily in Ireland.


The roe deer, on the other hand, as its scientific name Capreolus capreolus suggests, occupies a position on the other side of the deer family’s evolutionary divide, being a member of the subfamily Capreolinae. This little deer, then, which is comparable in size to the Chinese muntjac it shares Irish lands with, is actually a closer relative of forms like the massive, blob-nosed, and extravagantly-antlered moose. Its recent arrival in Ireland sees it pick up the torch once more to represent its subfamily in Ireland, this having been set down by the last member of Capreolinae to have roamed Irish lands, the reindeer, which died out at the end of the Ice Age or in the very early Holocene, over ten thousand years ago.


Ireland’s deer, then, provide us with yet another cautionary tale as regards trusting our eyes when it comes to assuming evolutionary relationships among the island’s mammals based on outward appearance alone. Similarities are often the result of two forms sharing a recent common ancestor, but they can also arise due to convergent evolution, retention of primitive features or re-evolution of them, etc. In the latter cases, appearances can be deceiving and our eyes can lead us astray, as, to borrow a phrase from the physicist Carlo Rovelli, reality is not what it seems.

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