The Cervini: Deer of Temperate Eurasia (and Beyond)

A couple of years back, I presented you with a post giving a quick overview of the classification of deer. For this post, I'm going to look a bit closer at a particular subgroup of deer: the species of the tribe Cervini.

Wapiti Cervus canadensis, photographed by Mongo.

For most people outside the Americas, a member of the Cervini will probably represent the first image that comes to mind when picturing a deer. The same goes for many Americans, for that matter, though in that part of the world they face a bit more competition. Cervins are the most diverse group of deer in temperate Eurasia, with representatives also being found in northernmost Africa, North America, India and southeast Asia (as well as introduced species in Australasia). The Monarch of the Glen was a cervin: specifically, a red deer Cervus elaphus. Bambi, in his Disney film incarnation, was also a cervin, a wapiti C. canadensis (in his original literary form, probably less familiar to modern audiences with little interest in Austrian novels about all the miserable ways that animals can die, he was a roe deer Capreolus capreolus and so not a cervin) (Edit: Scratch that, he's a apparently a non-cervin white-tailed deer, see comment below). The group has long been recognised by features of the skull and leg bones, and also is well supported by molecular data (Heckeberg 2020). Males produce antlers with multiple branches (at least in typical individuals) with the branches or tines usually directed forwards from the main shaft of the antler (the Père David's deer Elaphurus davidianus differs from other cervins in having the tines directed rearwards). The first of these branches, the brow tine, usually originates close to the base of the antler. In a number of Asian species, such as the chital Axis axis and sambar Cervus unicolor, there is usually on one more branch on the antler so each antler ends with three points. Species with such antlers are generally found in dense forests and their simpler antlers may represent an adaptation to these habitats (Heckeberg 2020). Other cervin species may have more extensively branched antlers with a tendency for antler complexity to correlate with overall body size; the largest living cervins, the red deer and wapiti, also have the most branched antlers. Larger extinct species had even more extravagant headgear with the apex of insanity being perhaps the bush-antlered deer Eucladoceros dicranios of the lower Pleistocene of Europe: each antler of this species might carry a dozen points.

Skull of Eucladoceros dicranios, photographed by Aldo Cavini Benedetti.

To describe the classification of cervins as having recently been in a state of flux is something of an understatement. A conservative presentation of the group may refer to thirteen or fourteen living species in four genera (e.g. Macdonald 1984). More recent authors, however, might refer to up to ten genera and nearly forty species. In a way, this difference is not really as dramatic as it may seem: multiple subspecies have long been recognised for most cervin species and some authors have argued for the recognition of many of these 'subspecies' as distinct species. Classification at generic level has mostly been affected by recognition that the genus Cervus as previously recognised is not monophyletic. Most recent authors agree on the recognition of at least four genera of Cervini (Cervus, Dama, Axis and Rucervus) with two further genera (Rusa and Elaphurus) also commonly recognised.

Persian fallow deer Dama mesopotamica, copyright Rufus46.

The genus Dama is usually recognised as including two species, the fallow deer D. dama and Persian fallow deer D. mesopotamica. These species are readily distinguished from other cervins by the form of their antlers which are distally palmate. Palmate antlers are also characteristic of the extinct giant Irish elk Megaloceros giganteus and many recent authors have regarded the two as closely related. The white spots that many deer species possess when young are commonly retained by fallow deer into adulthood though the coat will often become darker and the spots disappear during winter. Melanistic and leucistic individuals of fallow deer are also common. Defining the native range of the fallow deer is a bit of a tricky question. This inhabitant of open woodlands is currently widespread in Europe but was probably restricted to a region of the eastern Mediterranean during the last ice age. Its current range in northern Europe may in large part be the result of human transportation. The fallow deer has also been widely introduced elsewhere: herds may now be found in numerous locations in Africa, Australasia, North and South America. The Persian fallow deer, in contrast, is now endangered, its range restricted to a small number of localities in Iran. Indeed, it was once thought to be extinct prior to the rediscovery of a population of about two dozen individuals in the mid-1950s; the current population is perhaps only a few hundred.

Thorold's deer Cervus albirostris, copyright Heather Paul.

The genus Cervus in its current, more restricted sense includes the red deer and wapiti as well as the sika C. nippon* of eastern Asia. Sika are generally smaller than the other two species and, like fallow deer, usually retain the juvenile spots into adulthood. Excluding occasional small accessory branches, the antlers of sika also possess no more than four tines (Heckeberg 2020) in contrast to the commonly further branched antlers of red deer and wapiti. Four-tined antlers are also characteristic of the Thorold's or white-lipped deer C. albirostris, an inhabitant of the Tibetan Plateau that has sometimes been treated recently as the only representative of a separate genus Przewalskium. White-lipped deers have broad, cow-like hooves for navigating the steep, rocky slopes of their homeland. More commonly accepted classification-wise is the separation of two species found in southern Asia, the rusa C. rusa and sambar C. unicolor, as the genus Rusa. Both these species have three-tined antlers and their fawns lack spots.

*Commonly referred to as the sika deer. 'Sika' (or, as it's more commonly transliterated these days, 'shika') is Japanese for deer, so the common vernacular name of Cervus nippon is, indeed, 'deer deer'. The same issue arises for the rusa deer in Malay.

Chitals Axis axis, copyright Charles J. Sharp.

Axis is a genus of four species of smaller forest-dwelling deer found in southern Asia. Antlers are generally three-tined with the upper beams curving inwards towards each other. The chital remains spotted at maturity whereas the other species loose their spots. These species include the hog deer A. porcinus, named for its low, short-legged build, and two closely related insular species. Recent years have seen some authors separate the hog deers as a separate genus Hyelaphus, restricting Axis to the chital, owing to molecular phylogenies casting doubt on the genus' monophyly. However, it seems that these studies may have been mislead by a contaminated sample for the hog deer (Gilbert et al. 2006) and other studies have retained a monophyletic Axis. The thamin Rucervus eldii and barasingha R. duvauceli are also found in southern Asia where they tend to be associated with marshy habitats. Their antlers curve outwards then inwards to form a bow-shaped curve; those of the thamin are three-tined whereas the barasingha possesses further tines, sometimes up to ten on each antler. Again, some studies have questioned the monophyly of Rucervus and suggested the thamin be moved to a separate genus Panolia.

Père David's deers Elaphurus davidianus, copyright Peter O'Connor.

Finally, there is Père David's deer, arguably the weirdest of all the cervins, most often placed in its own genus Elaphurus but sometimes included in Cervus. By the time this species became known to European naturalists, it was already extinct in the wild, surviving only as a herd kept in a hunting garden near Peking belonging to the emperor of China. This herd was exterminated during the Boxer Rebellion but specimens that had been transported to Europe saved the species from total extinction. It is now widely kept in captive herds and has also been returned to the wild in a couple of locations in China. Père David's deer has a number of features that make it stand out from other deer: as well as the aforementioned backwards antlers, it has wide, splayed hooves and a remarkably long tail. But in other regards, Père David's deer is not anywhere as weird as it should be. In particular, its karyotype is very similar to that of the red deer: close enough, in fact, that not only are the two species capable of hybridising in captivity but the resulting hybrids are fully fertile (such matings are unlikely in the wild owing to the two species normally having different breeding seasons). Heckeberg (2020) found that Père David's deer was associated with Cervus species in analyses of nuclear genes and cranial characters but with Rucervus species in analyses of mitochondrial genes and dentition; other authors had previously found similar results. It has been suggested that these schizoid tendencies with regard to phylogenetic analysis might indicate a hybrid origin for Père David's deer from ancestors related to the wapiti on one side and the thamin on the other. Such a hybridisation event would have happened some time ago—fossils related to Père David's deer seem to date back at least to the late Pliocene—allowing enough time to pass for the new population to develop its own idiosyncracies not acquired directly from either parent.