Monday 2 April 2018

In a forest near Baxi in Sichuan: What Pika was this?

During a walk through a natural pine forest at an altitude of approximately 3,200 metres last November near Baxi in northern Sichuan we saw Chinese Grouse, Crested Tit-warbler, Przewalski’s Nuthatch, Grey Crested Tit, Giant Laughingthrush, Snowy-cheeked Laughingthrush and a flock of Sichuan Jays. A mature Sika stag appeared on the other side of a valley and Paul spotted three Yellow-throated Martens which left at high speed. But we also saw, and photographed, a pika. The question was: which species of pika?

A considerable amount of time has been spent and a considerable volume of email traffic has been generated in trying to determine the answer to that question. There have been false leads and false trails. The reason for that is severalfold: (i) we were in a little-studied area; (ii) the taxonomy and distribution of pikas is complicated and confused; (iii) published accounts of species and sightings are often inaccurate both in the scientific and popular literature; (iv) accounts of known types of habitat may be inaccurate or incomplete; (v) the similar appearance of a number of species.

Of one thing we were certain. The ear showed a narrow white margin.

Thomas's Pika
Photograph by Tim Melling

The most modern account of pikas is that in Handbook of Mammals of the World. Volume 6 published in 2016. This differs from the account and distribution maps shown in the standard field guide, published in 2008, since more has been discovered and some earlier errors sorted out. By locating Baxi Forest on the small-scale distribution maps in the Handbook (a major bend in the Yellow River provides a major feature to plot the position of Baxi), the following three species of pika, all with the white ear margin enter the field of possible candidates: Gansu Pika (Ochotona cansus), Tsing-ling (or Qinling) Pika (O. syrinx), Thomas’s Pika (O. thomasi).

From the Handbook of Mammals of the World, Volume 6, I have outlined the distributions of three species
of pika that are said to occur in the Baxi area plus the Moupin Pika now thought to occur to the south. Note
the discontinuous distribution. The published ranges of Thomas's, Gansu and Tsing-ling all incude Baxi.

'Our' pika has previously been identified by mammal watchers and photographers as the first and last of these as well as the Moupin Pika (O.thibetana). However, the latest published information is that the last species does not occur so far north.

The taxonomic scheme I am using here is that being used by IUCN and in the Handbook. It is based on the taxonomic revision published by Andrey Lissovsky of Moscow State University in 2014. Lissovsky had to pick apart a real can of worms found in past publications including lost type specimens, assignation of specimens or subspecies to a species without examination of the type specimens, the poor provenance of specimens used in DNA analysis as well as different interpretations made from examination of a limited number of specimens by earlier authors. He also did his own morphometric analysis on the skulls of 1090 pikas as well as an analysis of the cytochome b mitochondrial gene.

The detail of Lissovsky’s revision need not concern us. However, the three candidate species did emerge as full species, with the caveat that he recommended more work should be done on all but O. thomasi. A possible key finding, of relevance to our problem, is that Lissovsky showed that statistical analysis of all the skull measurements clearly distinguished Thomas’s Pika from those in the group which includes the Gansu, Tsing-ling as well as the Moupin Pika. The descriptions of Thomas’s Pika note the shape of the skull. Thus the Handbook states: ‘In general, Thomas’s Pika can be distinguished from all pika species by its elongated, narrow skull’.

We did not of course have another handy pika to compare ours with. However it is on the basis of the long, narrow skull that Vladimir Dinets an expert on the identification of Asian mammals with field experience in Sichuan also considers the species we saw as Thomas’s Pika. In an email to Sid Francis he did so also on the coloration of the throat. O. thomasi has a grey throat whereas O. syrinx has a rufous throat and chest. In addition, O. syrinx has a flat top to its skull.

Therefore, in terms of anatomy, pelage and distribution, it would seem our pika was indeed Thomas’s.

However, there is a problem in reconciling the identification as Thomas’s Pika with the published habitat of our animal. As I remarked earlier, our was in a natural pine forest. But the habitat stated in the Handbook and the field Guide is as follows: ‘Alpine shrub mountain zone at elevations of 2800-4100 m. Thomas’s Pika occurs in shrubby areas and does not penetrate subalpine meadows; it is a shrub dweller’ and ‘Inhabits hilly shrub forest (rhododendron, Salix, Caragana jubata, Potentilla fruticosa)…’. By contrast the habitat of the Gansu Pika is ‘subalpine meadows, inhabiting spare shrubs and thickets at forest edges’. But then the habitat of the Tsling-ling Pika is given as ‘forests at elevations of 1800-3100 m’. Initially I discounted Thomas’s because of the pine forest habitat of our pika. However, we were not far above the rhododendron forest so it is possible that the scrub forest habitat could extend to the scrubby understory of contiguous pine forest, possibly at different times of year. Indeed, Sid had seen the same species previously in nearby willow and rhododendron scrub forest. Clearly, more observations are necessary in the field but it does seem that a habitat extension is in order since O. thomasi may be found in pine forest too. Vladimir Dinets also noted that at another site he had found O. thomasi at higher elevations than O. syrinx; again this accords with our sighting at about 3,200 metres just outside the altitudinal range given for O. syrinx.

Vladimir Dinets shows photographs of pikas he has seen here.

Given the alleged presence of three small pika species with white ear margins in the Baxi area, we should expect each to occupy a different ecological niche and that the morphology of the skull should reflect that difference in habitat and the manner in which food is gathered in that habitat. O. thomasi has a long, narrow skull. This shape, one could predict with confidence, is related to its scrub forest habitat where grass, herbs and leaves would be nibbled out from between branches and stems. In short, Thomas’s Pika could be as adapted to life in the understory of a pine forest as to the scrub of a rhododendron forest.

I do not know whether the present taxonomy of the pikas will hold. All the molecular phylogeny is from mitochondrial DNA rather than or as well as nuclear DNA. We should, I suppose, expect to see a complicated picture for the number of species or lineages. The geological upheavals of the region are ones likely to have caused geographical isolation of populations, speciation or partial speciation and, possibly, later hybridization between temporarily isolated lineages.

Thomas’s Pika is endemic to China. It has the reputation of being rare but given its habitat that may be better expressed as rarely seen. It was first described in 1948 by the Russian zoologist A. I. Argyropulo in honour of Oldfield Thomas of the Natural History Museum in London. Thomas himself had named the Tsing-ling Pika, Ochotona syrinx*, in 1911; that specimen was collected on the Duke of Bedford's expedition. I will return to Oldfield Thomas in future posts on this blog.

So there we are. It does seem that our little pika, officially classified as ‘cute’ (but not quite so cute as the Plateau Pika) by its admirers in the Baxi Forest last November, was indeed Thomas’s Pika (Ochotona thomasi). Trying to identify and learn more about it has occupied a fair amount of time but uncovered how much more needs to be known about the natural history  and evolutionary history of these small mammals.

I am most grateful for the various exchanges and ideas being bounced around between Tim Melling (who also took the still photographs), Paul Markley and of course Sid Francis who also took us to the site. We can also give Sid the challenge of finding the other species of pika with white ear margins said to be in the Baxi area during his future trips. This is an area where citizen science can contribute to knowledge of little-studied species.

Finally, this is the video I took of the pika:

*With Lissovsky’s taxonomic revision and the application of the rule of priority to scientific names, the Tsing-ling Pika emerged as Ochotona syrinx. It was previously known as Ochotona huangensis but that name now appears to apply, as a junior synonym, to another species entirely:
As a consequence, the name for the taxon of pikas considered as a subspecies of Ochotona thibetana (Hoffmann 1993), or as the species O. huangensis (Yu et al. 2000, Hoffmann and Smith 2005) from the Qinling Mts, should be changed. The senior synonym for the pikas of the thibetana group from the territory, inhabited by taxon under discussion, is O. syrinx Thomas, 1911. According to the present analysis, the type specimen of O. syrinx from Tai Bai Shan Mt. within Qinling Range falls within the morphological variation of this thibetana-like taxon.… Thus, the valid name for this taxon should be O. syrinx.
Lissovsky AA. 2014. Taxonomic revision of pikas Ochotona (Lagomorpha, Mammalia) at the species level. Mammalia 78, 199-216.

Smith AT, Xie Y. (Editors). 2008. A Guide to the Mammals of China. Princeton University Press.

Wilson DE, Lacher TE, Mittermeier RA. 2016. Handbook of Mammals of the World. Volume 6. Lagomorphs and Rodents I. Barcelona: Lynx Edicions.

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