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Tetrapod Zoology

Tetrapod Zoology

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Eld's deer: endangered, persisting in fragmented populations, and morphologically weird... but it wasn't always so

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Eld's deer stag, by Raul654, used under Creative Commons Attribution-Share Alike 3.0 Unported license.

ResearchBlogging.org

This is Eld’s deer Cervus eldi* or the Brow-antlered deer, Thamin or Tamin, a moderately obscure, CITES-listed Old World deer discovered (by Lt. Percy Eld) in India in 1839. It was later found to occur in fragmented populations across much of south-east Asia and also in southern China. Fossils are known from Java and it seems that its original distributed was enormous, being mostly continuous across eastern India and Burma, Thailand, Laos, Cambodia and southern China.

* Many sources spell the specific name eldii but it seems that ‘eldi’ is correct. I’m putting the species in Cervus following Pitra et al. (2004).

Eld’s deer is fairly large (shoulder height is about 1.2 m, weight is 95-150 kg) with lyre-shaped antlers, the beams of which grow outwards before turning inwards. The brow tine is especially long, as hinted at by one of the common names, and appears to form a continuous curve with the beam “so that in profile the antlers appear to be bow-shaped” (Nowak 1999, p. 1108).

Eld’s deer has often been characterised as a tropical wetland specialist. However, this is not true when we look at all three recognised subspecies. In fact these different subspecies are pretty distinctive and again highlight the fact that ‘subspecies’ are not just entities invented for the purposes of bookkeeping but, rather, distinct lineages that we often need to pay attention to.

Cervus eldi eldi stag, antlers in velvet, quite possibly not photographed in the wild. Photo by Mongyamba, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

The Manipur subspecies (C. eldi eldi) [shown here] is a true wetland deer, possessing especially large, spreading hooves and peculiar cornified skin on the rest of the digits. It lives on thick, dense mats of floating vegetation known locally as ‘phum’ or ‘phumdi’ (Geist 1999) and is critically rare, being restricted to a tiny area about 15 km square. As of 2004, there were only about 180 individuals in the wild. About another 180 animals are kept in zoos. It was actually thought extinct prior to rediscovery in 1951.

Burmese brow-antlered deer (C. e. thamin), photographed at Zurich Zoo by Albinfo, licensed under Creative Commons Attribution-Share Alike 2.5 Generic license.

Meanwhile, the Burmese or Burma brow-antlered deer C. e. thamin and Thai brow-antlered deer C. e. siamensis are rather different, being animals of dry deciduous forests. This might negate suggestions that the Eld’s deer lineage as a whole is specialised for wetlands. However, there are suggestions that the modern habitat of the Burmese and Thai forms is not natural but the result of human persecution and the removal of their ancestral habitat due to agriculture (Lekagul & McNeely 1977). High nucleotide variation in these populations – similar to that of really widespread deer like roe and sika – suggests that both forms were previously very abundant and widespread (Balakrishnan et al. 2003), an observation that agrees with the idea that their ranges have been substantially decreased in historic times.

The Eld’s deer population on Hainan is sometimes recognised as the subspecies C. e. hainanus but the validity of this form was not supported by Balakrishnan et al. (2003). These authors found the Hainan population to be close to indisputable members of the Thai form and hence recommended included it within that subspecies.

That study (based on mtDNA analysis) also found the nominate subspecies to be closer to the Burmese form than to the Thai one. That’s surprising, since the latter two look extremely similar while the Manipur form is the really distinctive one. Furthermore, all three subspecies were distinct with little evidence for intermingling, and all three exhibit their own phylogeographic structure (Balakrishnan et al. 2003). While it therefore makes sense that all three be recognised as distinct genetic entities for the purposes of conservation and viability, the problem is that some of the populations (including the Manipur one and the Hainan C. e. siamensis one) now exhibit very low amounts of genetic variation and would probably benefit from increased genetic variation. It might therefore be appropriate to start moving animals around in order to increase the genetic health of the populations (Balakrishnan et al. 2003).

Eld's deer diorama at the AMNH. Photo by ideonexus, licensed under Creative Commons Attribution-Share Alike 2.0 Generic license.

A cervine – but what sort of cervine?

Eld’s deer looks odd, and for this reason Pocock (1943) decided that it should warrant it own genus. He therefore came up with Panolia for this species [UPDATE: see comments!! I was not aware of the new taxonomy used by Groves & Grubb (2011) while writing this article]. In overall appearance, though, Eld’s deer is not all that different from the Barasingha Rucervus duvauceli and the now extinct Schomburgk’s deer R. schomburgki (though antler form is different between the three, of course). Ellerman & Morrison-Scott (1951) and Geist (1999) therefore grouped all three together in Rucervus; Geist noted that these species shared relatively high antler mass, short tails, no rump patch, large, subhypsodont teeth specialised for grazing, and legs and feet specialised for soft ground.

Geist's (1999) depiction of the three supposed close relatives placed in Rucervus. L to r: Barasingha, Eld's deer, Schomburgk's deer. Compare the Eld's deer to the stag in the AMNH diorama shown above.

Cervid phylogeny from Pitra et al. (2004). You should be able to see the Eld's deer + Milu clade near the middle of the diagram. Click to enlarge.

However, these general morphological similarities might represent convergence rather than genuine affinity. Pitra et al. (2004) used data from mitochondrial DNA to look anew at Old World deer phylogeny and were most surprised to find Eld’s deer to group closely with the Milu or Père David’s deer C. davidianus, with both forming a clade that is the sister-group to a larger cervine clade that includes sika, red deer and sambar. Similar results were reported by Gilbert et al. (2006). This discovery may or may not support the inclusion of both Eld’s deer and Père David’s deer within Cervus (as usual, that's down to personal preference), but it does weaken the hypothesis that Eld’s deer is anything to do with Rucervus (which, following Pitra et al. (2004), I use here for the Barasingha and Schomburgk's deer alone. Rucervus seemingly forms a clade with Axis and is outside of Cervus). The grouping of Eld's deer with Père David’s deer also led to the curious idea that the latter might have arisen as a hybrid of Eld’s deer and a wapiti-type cervine – a subject that I covered in an article from last year devoted to Père David’s deer.

Sambar (Cervus unicolor), one of my favourite deer. Remind me to elaborate on that comment some time. Image by Wikigringo, licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license.

Of course, this phylogenetic hypothesis isn’t the only one out there. Ouithavon et al. (2009) found Eld’s deer to be especially close to the Sambar C. unicolor (though note that their sample was limited, since they were only analysing taxa present in Thailand). Most recently, Zhang & Zhang (2012) found Eld's deer to be the sister-taxon to a clade that included Père David’s deer as well as sambar, sika, red deer and so on.

There’s an important message to take from this quick look at what is now an obscure, little-known and endangered species, restricted to small populations and mostly famous for being weird. It’s that such obscure, endangered peculiarities might be the sorry relicts of what were once far more abundant, far more widespread populations. The data suggests that, just a few thousand or even few hundred years ago, Eld’s deer might have been a familiar, abundant and highly successful animal across an enormous area. Human impact on its diversity and distribution has been substantial.

Why did I write this article? Because obscure artiodactyls need more love, and I picked this species at random as one you don’t often hear about. Aiming to finish the petrel series soon, just haven't yet found the time.

For previous Tet Zoo articles on deer, see...

Refs - -

Balakrishnan, C. N., Monfort, S. L., Gaur, A., Singh, L. & Sorenson, M. D. 2003. Phylogeography and conservation genetics of Eld’s deer (Cervus eldi). Molecular Ecology 12, 1-10.

Ellerman, J. R. & Morrison-Scott, T. C. S. 1951. Checklist of Palaearctic and Indian Mammals, 1758 to 1947. British Museum (Natural History) Trustees, London.

Geist, V. 1999. Deer of the World. Swan Hill Press, Shrewsbury.

Gilbert, C., Ropiquet, A. & Hassanin, A. 2006. Mitochondrial and nuclear phylogenies of Cervidae (Mammalia, Ruminantia): systematics, morphology, and biogeography. Molecular Phylogenetics and Evolution 40, 101-117.

Lekagul, B. & McNeely, J. A. 1977. Mammals of Thailand. Kurushpa Ladprao Press, Bankok, Thailand.

Nowak, R. M. 1999. Walker’s Mammals of the World, Sixth Edition. The Johns Hopkins University Press, Baltimore and London.

Ouithavon, K., Bhumpakphan, N, Denduangboripant, J., Siriaroonrat, B. & Trakulnaleamsai, S. 2009. An analysis of the phylogenetic relationship of Thai cervids inferred from nucleotide sequences of protein kinase C iota (PRKCI) intron. Kasetsart J. (Nat. Sci.) 43, 709-719.

Pitra, C., Fickel, J., Meijaard, E., & Groves, C. (2004). Evolution and phylogeny of old world deer Molecular Phylogenetics and Evolution, 33 (3), 880-895 DOI: 10.1016/j.ympev.2004.07.013

Pocock, R. I. 1943. The larger deer of British India. Part II. Journal of the Bombay Natural History Society 43, 553-572.

Zhang, W.-Q. & Zhang, M.-H. 2012. Phylogeny and evolution of Cervidae based on complete mitochondrial genomes. Genetics and Molecular Research 11, 628-635.

The views expressed are those of the author and are not necessarily those of Scientific American.

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