The Military Surgeon’s White Squirrel of Siam

This text may start as a part of a quiz: What mammal of surprising coloration connects a mission to Thailand, when it was Siam, and a Scottish physician to my dad and mom’ backyard within the early Sixties?

The reply is Finlayson’s Squirrel. Callosciurus finlaysonii is uncommon for 2 causes. The primary is that it is available in all kinds of color types in numerous elements of its vary in south-east Asia. The second is that in a kind of color types the color of the pelage is solely white.

Finlayson’s Squirrel, photographed in Saraburi, Thailand
{Photograph} from the mission Noah Web site*

It was this white kind that was seen and picked up by George Finlayson in southern Thailand. He was the surgeon and naturalist to a lower than profitable commerce/diplomatic mission from the East India Firm to Siam and Cochin China (Vietnam) led by John Crawfurd (1783-1868) and comprising the next members of the Indian Military plus Mrs Crawfurd: Captain Frederick Dangerfield (1789-1828) was assistant head; he had established a reputation for himself as a surveyor and geologist; Lieutenant Walter Rutherford (1801-1856) was in control of thirty sepoys. So far as I can verify all members of the mission—other than the sepoys—have been Scottish or of Scottish descent.

George Finlayson was born in Thurso in 1790. He turned clerk to Dr Somerville, head of the military medical employees in Scotland in the course of the Napoleonic wars. He did so in succession to his elder brother, Donald, who Somerville had moved on to the military medical service, such have been his abilities. This was a time when clerks served successfully as medical apprentices. George adopted Donald into the military. Donald served within the engagements previous, and at, the Battle of Waterloo however then got here to a tragic finish. He was assistant-surgeon to the thirty third Regiment of Foot however disappeared as the military marched on to Paris. It was thought Donald had fallen to marauders following within the wake of the retreating French military. George took depart to seek for his brother however may discover no hint. He was so distraught that the military, at Dr Somerville’s suggestion, moved him to the medical employees about to depart for Ceylon (Sri Lanka). As soon as there he threw himself into the pursuit of pure historical past. In 1819, he moved to India as assistant-surgeon to the eighth Gentle Dragoons then stationed at Meerut.

So as to keep in India for Crawfurd’s mission, when his regiment sailed again to Britain after its service in India, Finlayson moved to a distinct regiment.

After the mission in south-east Asia, George Finlayson rapidly succumbed to what he self-diagnosed as phthisis—tuberculosis, because it later turned recognized. He died on the passage from Calcutta to London on the East India Firm’s ship, Normal Hewett, in 1823.

Finlayson had written an account of the Crawfurd Mission. It was printed in 1826 with a ‘Memoir of the Creator’ written by Sir Stamford Raffles (1781-1826), founder of recent Singapore and of the Zoological Society of London. Raffles clearly thought very extremely of Finlayson.

Finlayson had launched into Normal Hewett with the specimens he had collected, together with a white squirrel, destined for the museum of the East India Firm which was in Leadenhall Avenue in London. The Keeper was one other pal of Raffles, Thomas Horsfield (1773-1859). There Horsfield described the squirrel and named it after Finlayson as Sciurus finlaysonii. He started his description with a citation from Buffon:

Sc. lacteus dorso flavescente, oculis vibrissis palmis plantisque nigris, cauda pilis nigris raris interspersa.

Ecureuil blanc de Siam, Buff. Hist. Nat. VII. p. 256.

Which interprets as: a squirrel, milky with a yellow again; vibrissi, palms, plantar surfaces of ft black, a furry tail interspersed with uncommon blacks.

Horsfield continued:

This species is devoted to the reminiscence of Dr. George Finlayson, (of His Majesty’s 59th [2nd Nottinghamshire] Regiment [of Foot],) the naturalist, who accompanied John Crawfurd, Esq. in his mission to Siam and Cochin-China. His well being was in a precarious state, from the consequences of an Indian local weather; and now we have to lament that he didn’t reside to return to his native nation.

This species has hitherto been talked about by Buffon alone [in 1789], from the next concise discover in P. Tachard’s Travels. “Nous y (at Lonpeen, a village located within the in depth forests of Siam) vimes aussi des Ecureuils, qui ont le poil parfaitement blanc et la peau tres-noire.”—Second Voyage du P. Tachard, Paris, 1689, p. 249.

The next description is extracted from Dr. Finlayson’s manuscripts:—“The pinnacle and physique yellowish white; the top spherical; the cheeks full; the nostril massive ; the ears massive, plain, not tufted; the iris darkish brown; the whiskers lengthy and black; the tail bushy, interspersed with black hairs, and tufted; palms of the ft black. That is a chic, full of life, and lively species of Squirrel, nearly completely white. The physique is about seven inches in size, and the tail is equal in size to the physique. The eyes are black and full of life; and the animal, although white, has not the leucæthiopic behavior frequent within the animals of Siam. It frequents massive bushes, feeds on their bark and fruit, and is mostly seen upon a tall species of Aleurites. One of many specimens was shot by Lieut. Rutherford, on the Islands referred to as Sichang, within the Gulf of Siam.”

The India Museum closed in 1879 and the specimens transferred to what’s now the Pure Historical past Museum in South Kensington. And there the sort specimen—the one shot by Lieutenant Rutherford on the island now generally known as Koh Si Chang—may be discovered, catalogued beneath its unique scientific identify of Sciurus finlaysonii. In his journal, Finlayson famous that on the group of islands that features Koh Si Chang:

The [squirrel] is uncommon, about eight inches in size; an lively, full of life, and good-looking animal.

On the morning of the thirteenth [August 1822) we landed on the principal island, in pursuit of white squirrels. 

Moving to the 21st century, Finlayson’s Squirrel is now known to vary widely in the coloration of its fur. It varies geographically (the basis of the erection of numerous subspecies, 16 of which are currently recognised). It varies within populations and it varies according to season. Coloration across its range (Burma/Myanmar, Laos, Cambodia, Vietnam and centred in Thailand) varies widely including, as well as white, black, red and agouti. Intergrades between these forms have also been seen where populations meet. An example of variation within a population is in C. f. bocourti, common in Bangkok parks. Individuals may be dark on the dorsal surfaces of the body and forelimbs or entirely white. Variation with season has been described in a population that is maroon-red at one time of year and white at another. Charles Francis in his book published in 2008 made the point that there is a need for more observations in the field and for molecular genetic studies. A key question, of course, is whether all the Finlayson’s Squirrels currently labelled as such are indeed of a single species and whether other forms currently included in different species should be moved to C. finlaysonii. Possible reasons for the great variation in colour and pattern do not seem to have been explored and one can only speculate on the selective forces at play.

George Finlayson realised that white squirrels were present in southern Thailand as well as on the island of Si Chang. It just happens that the formal description of the species was from one shot on Koh Si Chang.

The variations in colour have been shown in several books and papers:

From Francis 2008 – see below

From Wilson, Lacher & Mittermeier 2016 – see below

The coloration of the species varies so much that the name Variable Squirrel has been used and indeed adopted by IUCN for its Red List. Why they should do that when everybody worth knowing has always called it Finlayson’s Squirrel I do not know.

Distribution of Finlayson’s Squirrel
Adapted from the IUCN Red List

Horsfield’s use of -ii for the genitive of Finlayson in its specific name of finlaysonii is not the preferred form. Most, and certainly modern usage, would be finlaysoni, the single -i. As the latter it has often appeared in scientific papers and books including Walker’s Mammals of the World in at least some of the editions published since 1964.  However the rules are such that it is also incorrect to change it to the single -i. C. finlaysonii is the original spelling and therefore retained.

Unlike the vast majority of animals that I have kept over the past 65 years I cannot recall how I obtained a female Finlayson’s Squirrel in 1960 or 1961. Had I known then what I know now I would not have done so. Variegated Squirrel Bornavirus 1 (VSBV-1) was first reported in 2015 following reports of the three human deaths in Germany between 2011 and 2013 from of a previously unknown encephalitis. The novel virus was isolated from tissues of a Variegated Squirrel, Sciurus variegatoides, native to Central America, owned by one of those who had died. The virus has since been found in other captive squirrels, including C. finlaysonii and Prevost’s Squirrel (Callosciurus prevostii), in collections in Germany, the Netherlands and Croatia. Those who died were breeders of squirrels, were known to each other and belonged to a squirrel breeding association where they met regularly. Another fatal case occurred in a zoo keeper in Germany, with the virus being found in a Prevost’s Squirrel in the collection. The whole history of the appearance and evolution of the virus has been investigated by studying the molecular epidemiology, together with the activities of the individual keepers and the movement of animals between breeders and from the breeders to private keepers and zoos. Current evidence indicates that a Prevost’s Squirrel was responsible for the primary introduction of the virus.

Prevost’s Squirrels, a beautifully marked species, were commonly available from animal dealers in the 20th century. I have seen them for sale recently in UK and several zoos breed them. I do hope they are all tested, since the fate for those keepers who have caught VSBV-1 has been dire. Fortunately, there have been no cases of human-human infection reported. I do wonder if there have been unreported cases of encephalitis of unknown aetiology from keepers of other species of Callosciurus. For example, In Hong Kong, Pallas’s Squirrel (C. erythraeus) was a popular pet, kept in small cages in small flats and, therefore, in close proximity to the human inhabitants.

Since the discovery of VSBV-1 there has been considerable work in Europe to follow-up these findings with surveys of wild squirrels, zoo workers and the wider human population.

Returning to my Finlayson’s Squirrel of the early 1960s, it was an unsatisfactory addition for the simple reason is that it only appeared from its sleeping box at first light for a short run around its capacious outdoor cage and to eat. Except on rare occasions it stayed in its box for the rest of the day, summer and winter, for years. Only much later did I realise how it could survive on one meal a day. In the wild they are known to eat fruit, seeds, bark, buds, flowers and sap, all of low energy density. I gave the sort of mixture suitable for rabbits or rats: biscuit, wheat, maize, oats, sunflower seed and the like plus fruit like apples and vitamin supplements. All the former have 4-5 times the energy density of tropical fruits. It did not need to emerge for more food and it never or hardly ever did so even in the depths of winter. By contrast, I have seen photographs of tame Finlayson’s Squirrels reared in captivity.

All I remember from around that time is that the Finlayson’s Squirrels were advertised as white. Only much later did I find that not all Finlayson’s Squirrels are white. My guess is that importers wanted white squirrels and that whoever was exporting them from Thailand sorted them accordingly. 

As far as I can recall Finlayson’s Squirrels were only imported into Britain for a relatively short period from around 1960. However, they have now become naturalised as a result of releases/escapes in Singapore, in two areas of Italy from the 1980s, and the Philippines. Genetic evidence suggests they are also present amongst the introduced squirrels of Japan. In short, there is great concern in those regions that they have become a problem as an ‘invasive species’.


Cadar D, Allendorf V, Schulze V, Ulrich RG, Schlottau K, Ebinger A, Hoffmann B, Hoffmann D, Rubbenstroth D, Ismer G, Kibbey C, Marthaler A, Rissland J, Leypoldt F, Stangel M, Schmidt-Chanasit J, Conraths FJ, Beer M, Homeier-Bachmann T, Tappe D. 2021. Introduction and spread of variegated squirrel bornavirus 1 (VSBV-1) between exotic squirrels and spill-over infections to humans in Germany. Emerging Microbes & Infections 10 doi: 10.1080/22221751.2021.1902752 

Finlayson G. 1826. The Mission to Siam, and Hué the Capital of Cochin China in the Years 1821-2. London: John Murray.

Francis CM. 2008. A Guide to the Mammals of Southeast Asia. Princeton: Princeton University Press.

Horsfield T. 1824. Zoological Researches in Java and the Neighbouring Islands. London.

Mazzamuto MV, Wauters LA, Koprowski JL. 2021. Exotic pet trade as a cause of biological Invasions: the case of tree squirrels of the genus Callosciurus. Biolog 10, 1046. doi:10.3390/ biology10101046 

Public Health England. 2019. Human Animal Infections and Risk Surveillance group. Qualitative assessment of the risk that variegated squirrel bornavirus 1 presents to the UK population.

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

Leave a Reply

Your email address will not be published. Required fields are marked *