Water Deer Taxonomy - Discovery & Naming

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Water deer one

The earliest surviving written record of water deer of which I'm aware dates to 239 BC China. In the Lüshi Chunqiu, an encyclopaedic Chinese text covering a range of subjects from music to agriculture and compiled under the patronage of Qin Dynasty businessman and politician Chancellor Lü Buwei, is a reference to the Zhang (a Chinese word for deer - see below): a small animal that runs faster than a horse, but stops to look back often. Much later, around 1116, Szchewan physician Tang Shen-wei published a volume of the Pên-ts'ao in which he told of two different kinds of zhang living in hillside grassland; those with and those without canine teeth that aren't used for chewing. (Shen-wei was presumably mistaking females and adolescent males as a separate species.) Early literature aside, it would be just over 750 years after Shen-wei's reference before the water deer we recognise today would be formally described.

Born in India, Robert Swinhoe was a naturalist who travelled widely through Asia and reported regularly to the Zoological Society of London. On 27^th March 1865, he wrote to the Society to relay, amongst other news, a report he had received while in Formosa (modern day Taiwan) from a friend telling of large herds of a “hog deer” that were common on an island in the Yangtze river that “lurks about in the bushes and high coarse grass” having swum across to the island at the flooding of the great river. At the time, Swinhoe thought his friend was referring to Hyelaphus porcinus, the hog deer native to India. Upon visiting a market in Shanghai on 30th November 1868, however, he found one of these deer for sale and realised that it was something entirely different.

Swinhoe returned home with the skin and skull of a buck (currently the “type” specimen for the species held at the British Museum) and the skulls of two does, all taken on “Deer Island” in the Yangtze River, a few miles upstream from Chinkiang (now Zhenjiang) in central eastern China. He presented these to the Society in 1870, writing in his paper to the Proceedings of the Zoological Society of London:

“These [skulls and skin] I beg to exhibit to this Meeting, and to propose for this new Deer the specific term of inermis, from its hornless state, and to place it under a new genus, for which I would suggest the name Hydropotes, or Water-drinker, from the love of the animal for marshy ground.”

Interestingly, there was some debate about where Swinhoe first published his account of the water deer. The Proceedings paper is dated 10^th February 1870 and most texts cite this as the original reference for the species, but it appears that this issue of the journal was actually published in the summer of that year. In their round-up of problems in vertebrate nomenclature, published in an Italian journal during 1989, Ian McAllan and Murray Bruce note that Swinhoe first wrote of his discovery in the 19^th February 1870 edition of Anthenaeum, a weekly literary magazine published in London, and his paper to the Proceedings wasn't published until June. One assumes that this probably just reflects the delay in academic publishing that many scientists will be familiar with today, and that the meeting was in fact held in February, but in taxonomic circles the Anthenaeum holds the accolade of being the first published account of this species.

In the late nineteenth and early twentieth century, several different species of water deer were described. In 1872, Sir Victor Brooke described Hydropotes affinis, while Pierre Marie Heude argued that Hydropotes argyropus from Korea was distinct in 1884 (see below) and Von Max Hilzheimer, at the University of Strasbourg, presented Hydropotes kreyenbergi in Zoologischer Anzeiger during 1906, based on an animal shot in Hankou, China two years earlier. In his German paper, Hilzheimer argued that based on, among other features, a much more arched skull, shorter nose, higher orbital rim and shape, and position of the lacrimal gland, kreyenbergi was “well-differentiated” from Brooke's affinis. Hilzheimer named the deer after Dr Kreyenberg, who shot it and presented it to the Zoological Museum in Berlin. At the time of writing, all these species are now considered synonyms of (i.e., the same species as) Hydropotes inermis.

A deer by any other name?

Before we delve into the taxonomy of water deer, it is worth mentioning that while we know Swinhoe created the new genus Hydropotes to house the species, some older texts refer to it as Hydrelaphus, meaning quite literally “water deer”.

Richard Lydekker was the first to present the water deer under the “new name” of Hydrelaphus inermis in his The Deer of All Lands, published in 1898. In the book Lydekker didn't explain the sudden change, having used Hydropotes in the second volume of his The Royal Natural History four years earlier. In a German paper to Abhandlungen und Berichte some seven years later, however, Hilzheimer noted that Lydekker renamed Hydropotes to Hydrelaphus because Hydropota was already in use as a genus of flies, having been established by Italian entomologist Camillo Róndani in 1861. Similarity in naming is not sufficient for justification for renaming a taxon, however, and as the ICZN (the governing body for animal taxonomy) recognise the two as distinct, the change was unnecessary. Consequently, Hilzheimer changed it back, arguing that “even if there are hydropods, this resemblance is no reason to deviate from the laws of priority”. Nonetheless, several older texts and even some websites refer to water deer as Hydrelaphus.

The musk connection?

The lack of antlers and presence of large canine teeth gives the water deer a rather unusual appearance for a deer, and one could be forgiven for thinking this small cervid actually belonged in the Moschidae family with the musk deer of the mountainous forests and alpine scrub of southern Asia. Indeed, some early observers noted the similarities in appearance and, in his description of Hydropotes kreyenbergi, Hilzheimer noted that this animal was called “Moschusböckchen ohne Moschus”, or the ‘muskbuck without musk'.

Despite a few early naturalists, such as John Edward Gray in his Catalogue of ruminant Mammalia (Pecora, Linnaeus) in the British Museum, published in 1872, considering water deer to be taxonomically allied with musk deer, on the whole there was plenty of anatomical evidence, even early on, that the similarities were superficial. Even in his initial description of the species, Swinhoe alluded to this, noting that the upper canine teeth were “tusk-like, as in Moschus, but not so developed”. Subsequent descriptions from dissection and skeletal analysis confirmed several differences in the anatomy of the skull, digestive system and heart and brain morphology that clearly differentiated Hydropotes from Moschus, placing it confidently within the Cervidae.

Probably the final word on this separation was had by Alfred Garrod in 1877 and William Forbes in 1882, successive prosectors of the Zoological Society of London, each of whom argued convincingly that water deer couldn't be placed within the Moschidae despite the similarities in appearance and were clearly members of the Cervidae. Today, thanks to the advances in genetic analyses, we have yet more data to confirm water deer are “true deer”, while the striking G-banding pattern homology of the Moschus karyotype presented by Italian zoologists Francesco Fontana and Michele Rubini in 1990 suggests musk deer are most closely related to the bovids, and together they form the sister group to the Cervidae. This hypothesis was supported by an analysis of just over 5,300 nucleotides from 23 species conducted by Alexandre Hassanin and Emmanuel Douzery and published in Systematic Biology during 2003. The DNA data cluster the Bovidae and Moschidae together as sister taxa and indicate that they diverged from the Cervidae about 27.5 mya, during the Late Oligocene.