Callosciurus finlaysonii (Finlayson's squirrel)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Economic Impact
- Environmental Impact
- Risk and Impact Factors
- Uses List
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Links to Websites
- Principal Source
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Callosciurus finlaysonii (Horsfield, 1824)
Preferred Common Name
- Finlayson's squirrel
Other Scientific Names
- Sciurus finlaysonii Horsfield 1823
International Common Names
- French: écureuil de Finlayson
Local Common Names
- Germany: Finlayson-Hornchen
- Italy: scoiattalo di Finlayson; scoiattolo variabile
Summary of InvasivenessTop of page
C. finlaysonii is a squirrel native to Thailand, Myanmar, Laos, Cambodia and Vietnam. It has been introduced to Italy (Bertolino et al. 2000; Aloise and Bertolino, 2005; Rima et al. 2007), Singapore and Japan (Oshida et al., 2007; Kuramoto et al. 2012), and is considered invasive in Italy and Japan. It is a species of lowland forests (Moore and Tate, 1965) as well as open woods and coconut plantations (Lekagul and McNeely, 1988). In Italy it is known to inhabit urban parks and pine woodlands, and to feed on Ceratonia siliqua, Pinus halepensis,P. pinea, Quercus virgiliana, Q. ilex, Olea europea and all kinds of fruit (Aloise and Bertolino, 2005).. Its presence in Italy has also been linked to severe damage as a result of bark-stripping behaviour of both deciduous and conifer trees, which can in severe cases kill trees (Aloise and Bertolino 2005; Rima et al., 2007; Mori et al., 2016).C. finlaysonii is listed on the IUCN Red list (IUCN, 2014) as 'least concern' due to its wide distribution.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Mammalia
- Order: Rodentia
- Family: Sciuridae
- Genus: Callosciurus
- Species: Callosciurus finlaysonii
Notes on Taxonomy and NomenclatureTop of page
There have been no recent taxonomic revisions; but see Steppan et al. (2004) for an assessment of the phylogeny of squirrels using two nuclear genes (c-myc and RAG1). Their results show the tribe Callosciurini to be a monophyletic group, but suggested a re-ordering of subfamilies and tribes within the family Sciuridae, including the creation of the subfamily Callosciurinae containing the tribe Callosciurini and the tribe Funambulini.
Species taxonomy was initially revised by Moore and Tate (1965) and then revised and expanded to include C. finlaysonii ferrugineus by Corbet and Hill (1992). For differences between subspecies, see Detection and Inspection.
DescriptionTop of page
Coat colour is highly variable (for descriptions of subspecies see Detection and Inspection; for detailed coat colour descriptions see Moore and Tate (1965) and Corbet and Hill (1992). Timmins and Duckworth (2008) provided descriptions for subspecies in Laos). Morphological details of adult C. finlaysonii are shown in the table below.
Table 1: Morphological data from different studies for body mass (g), head to body length (mm), and tail length for adult males (M), females (F) and individuals of unknown sex (U). Sample sizes where known are given in brackets after the values.
Moore and Tate, 1965
Range across subspecies
Corbet and Hill, 1992
Range across subspecies
Kitamura et al., 2004
Moore (1961) noted the presence of three pairs of mammae, typical for Callosciurus species in the Indo-Chinese subregion. Observed hind-foot length range across subspecies are 44-58 mm (Moore and Tate, 1965) and 46.99-53.34 mm (Blanford 1888-1891). C. finlyasonii williamsoni and C. finlaysonii bocourti had the greatest reported skull length at 52.2 and 52.7 mm respectively and C. finlaysonii finlaysonii the shortest at 45.5mm (Moore and Tate, 1965). Corbet and Hill (1992) gave the range of skull length for this species as 44-57 mm.
The baculum in the subfamily Callosciurus is unique and characterised by a sharp-edged accessory blade attached to its dorsal surface (Corbet and Hill, 1992). The baculum of C. finlaysonii is long and slender (Corbet and Hill, 1992).
DistributionTop of page
C. finlaysonii is native to Cambodia, Laos, Myanmar, Thailand and Vietnam. Corbet and Hill (1992) and Thorington et al. (2012) provided information on mainland and insular subspecies distributions in Thailand, Myanmar, Burma, Laos and Cambodia (see Detection and Inspection). C. finlaysonii has been introduced to Singapore (Thorington et al., 2012), Italy (Bertolino et al., 2000) and Honshu, Japan (Kuramoto et al., 2012). No source references are provided for the introduction to Singapore and the current status of this population is unclear, although it was listed as introduced by the Singapore Government (2014).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Cambodia||Present||Native||Corbet and Hill, 1992; Thorington et al., 2012||Subspecies C. f. annellatus and C. f. cinnanoneus|
|Japan||Present||Present based on regional distribution.|
|-Honshu||Present||Introduced||Invasive||Kuramoto et al., 2012|
|Laos||Present||Native||Thorington et al., 2012|
|Myanmar||Present||Native||Corbet and Hill, 1992; Thorington et al., 2012||Subspecies C. f. ferrugineus; geographically isolated|
|Singapore||Present||Introduced||Thorington et al., 2012|
|Thailand||Present||Native||Corbet and Hill, 1992; Thorington et al., 2012||Mainland and islands of Si Chang, Phai, Tut|
|Vietnam||Present||Native||Corbet and Hill, 1992; Thorington et al., 2012||Subspecies C. f. germaini, C. f. harmandi on islands of Phu Quoc and Condor respectively|
|Italy||Present||Introduced||Invasive||Thorington et al., 2012; Bertolino and Lurz, 2013||See text section|
History of Introduction and SpreadTop of page
No detailed information is available for the introductions of C. finlaysonii in Singapore or Japan, although Yanagawa (2000) did report the sale of squirrels as pets in Japan. In Italy, four individuals were released in a 2 ha urban park at Aqui Terme, northwest Italy, in 1981 (Bertolino et al., 1999), and 3-4 pairs of C. finlaysonii were introduced in southern Italy at Maratea, Basilicata region, in the mid-1980s (Rima et al., 2007). Bertolino et al. (1999) identified the subspecies in northwest Italy as C. finlaysonii bocourti. Both populations are reported to be increasing, the one at Maratea exponentially (Bertolino et al., 2000).
There was initially some uncertainty whether the species was introduced to Japan. Oshida et al. (2007) carried out a preliminary genetics study to determine the origin of introduced Callosciurus to Japan. Their findings identified two genetic lineages (A and B). Lineage A was found to be related to C. finalysoni. Precise species identifications, however, proved difficult due to the high level of variability in Callosciurus species and subspecies, and the occurrence of hybridisation and gene introgression between subspecies and species. However, the introduction of C. finlaysonii to Japan was confirmed by further work by Kuramoto et al. (2012), using mitochondrial DNA. All 83 individuals from the Callosciurus population at Hamamatsu, Shizuoka Prefecture, tested had C. finalysonii haplotypes. The 'CfJ1' haplotype, present in 25% of the animals, has also been reported from C. finlaysonii boonsongi in north-eastern Thailand, and the authors speculate that the population in Japan may have been imported from Thailand via Bangkok (Kuramoto et al., 2012).
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Italy||1981-1986||Ornamental purposes (pathway cause)||Yes||No||Bertolino et al. (2000)|
|Japan||Thailand||Yes||No||Kuramoto et al. (2012)||C finlaysonii traded as pets around 2000; mtDNA haplotype match C. f. boonsongi from north-eastern Thailand|
Risk of IntroductionTop of page
In both Italy and Japan, where C. finlaysonii is considered invasive, the pet trade seems a high risk pathway for introduction. Experience with tree squirrel species has shown that animals obtained through the pet trade are a prime source for continued human-mediated, deliberate releases that greatly assist in the successful spread of the species involved (e.g. Martinoli et al., 2010; Bertolino and Lurz, 2013). No information is available from Singapore.
HabitatTop of page
There are few detailed descriptions on habitat preferences aside from broad descriptions that link the species to a wide range of forest habitats, such as open woods, coconut plantations, and dense forest (Lekagul and McNeely, 1988). Specific examples of habitat include moist evergreen forests of elevations between 600-800 m in Khao Yai National park, Thailand (Suzuki et al., 2006; see also Kitamura et al. 2004), mixed deciduous and dry dipterocarp forest in Mae Hong Son Province, northern Thailand at elevations of 800-1200 m (Watanaratchakit and Srikosamatara, 2006), and lowland mixed forests (especially fruit trees) on the island of Phu Quoc, Vietnam (Abramov et al., 2007).
Duckworth et al. (2008) considered C. finlaysonii highly tolerant of degradation and fragmentation.
Habitat ListTop of page
|Terrestrial – Managed||Managed forests, plantations and orchards||Secondary/tolerated habitat|
|Urban / peri-urban areas||Present, no further details|
|Terrestrial ‑ Natural / Semi-natural||Natural forests||Principal habitat|
Biology and EcologyTop of page
Chromosomes have been described by Nadler et al. (1975): C. finlaysonii has 2n = 40, and the karyotype is comprised of six pairs of metacentric, 10 of submetacentric and three pairs of acrocentric autosomes, one of which bearing satellites (Nadler et al., 1975). A re-examination by Tanomtong et al. (2009) based on the subspecies C. finlaysonii bocourti supported the number of diploid chromosomes being 2n=40, and provided more detail in the description of autosomes: four large metacentric, four large submetacentric, 14 large acrocentric, two medium telocentric, four small metacentric, six small acrocentric and four small telocentric chromosomes (Tanomtong et al., 2009).
Oshida et al. (2001) studied the molecular phylogeny of five squirrel species in the genus Callosciurus based on cytochrome B sequences. Their findings indicated two lineages, one containing C. erythraeus, C. caniceps and C. finlaysonii, and the other containing C. nigovittatus and C. prevostii. Whilst these results support Moore's (1961) division of Callosciurus species, based on morphological characteristics, into a mainland and a Sundaland unit, Oshida et al. (2001) did not rule out the possibility of other geographical lineages pending a comprehensive analysis of all 15 described species of Callosciurus.
Reproductive behaviour and mating strategies unknown. One reported litter size of two (Hayssen, 2008b).
In Thailand C. finlaysonii is diurnal and probably most active in the afternoon (Suzuki et al., 2006).
Nutrition and seed dispersal
Known dietary items include tree seeds and fruits (Kitamura et al., 2004; 2006; Rima et al., 2007). Kitamura et al. (2004; 2006) suggested that C. finlaysonii eats Canarium euphyllum fruits and seeds, and is a short distance seed disperser for Aglaia spectabilis in moist evergreen forests in Thailand.
D'Ovidio et al. (2014) reported finding eggs of the parasitic flatworm Dicrocoelium dendriticum in two pet C. finlaysonii in Italy.
ClimateTop of page
|Af - Tropical rainforest climate||Preferred||> 60mm precipitation per month|
|Cs - Warm temperate climate with dry summer||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
Notes on Natural EnemiesTop of page
There is no specific mention of particular predators in the literature (see Research needs); however, key natural enemies are likely to be small to medium-sized mammalian predators, birds of prey and snakes.
Means of Movement and DispersalTop of page
The pet trade appears a high-risk pathway for long distance dispersal and introductions of C. finlaysonii beyond its natural range.
Pathway CausesTop of page
Pathway VectorsTop of page
Economic ImpactTop of page
There are no detailed accounts of economic impacts for C. finlaysonii across its native range, although the species' presence in coconut plantations (Lekagul and Ncneely, 1988) may suggest the potential for damage.
In Italy, C. finlaysonii has been linked to extensive, if currently localized, damage to trees through bark-stripping behaviour. The animals strip the bark of trees to obtain access to sap bearing tissue. Damage that girdles the stems or trunk can kill parts of the tree, or even the whole tree if this happens on the main trunk. Bark-stripping damage can also facilitate secondary infections (such as fungal infections) and reduce the economic value of timber. Affected tree species in Italy include Certonia siliqua, Quercus virgiliana, Q. ilex, Olea europea and Pinus halepensis (Aloise and Bertolino, 2005; Mori et al., 2016).
Environmental ImpactTop of page
In Italy the localized presence of C. finalysonii is linked to severe damage to trees through bark-stripping behavior, with an estimated 80% of trees damaged in the urban park where they were first introduced in northern Italy. Damage to trees has also been recorded in the other area of introduction in southern Italy. In severe cases extensive damage can kill trees (Bertolino et al., 2000).
Introduced populations in Italy, Japan and Singapore are still localized and often there is a lag effect with respect to population expansion linked to squirrel introductions with small founder sizes (e.g. Lurz et al., 2001; Wood et al., 2007). Broader biodiversity or ecosystem impacts tend to occur once the population expands. Both in Italy and in Japan Callosciurus squirrels are expanding their range and are considered invasive.
Tree squirrel and other rodent introductions have been linked to the introduction of novel parasites and diseases including the spread of zoonotic disease (e.g. Khodakevich et al., 1986; Langkop et al., 2003; Dozière et al. 2010; Romeo et al., 2014). Whilst there are currently no data for C. finlaysonii finlaysonii due to a lack of studies, the risk of disease transmission, and introduced individuals acting as vectors for parasites and diseases that can harm native wildlife (and potentially humans) should not be ignored.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Is a habitat generalist
- Capable of securing and ingesting a wide range of food
- Highly mobile locally
- Benefits from human association (i.e. it is a human commensal)
- Has high reproductive potential
- Damaged ecosystem services
- Negatively impacts forestry
- Reduced native biodiversity
- Competition - monopolizing resources
- Pest and disease transmission
- Highly likely to be transported internationally deliberately
- Difficult to identify/detect in the field
- Difficult/costly to control
Uses ListTop of page
- Botanical garden/zoo
- Research model
- Sport (hunting, shooting, fishing, racing)
Detection and InspectionTop of page
C. finlaysonii nox - from a small coastal area of Thailand, near Cape Liant. Coat is entirely black.
C. finlaysonii cinnamomeus (encompasses subspecies C. finlaysonii splendens and C. finlaysonii herberti) - from south-east Thailand and south-west Cambodia. Coat is all red or with a small amount of olive agouti on head and limbs.
C. finlaysonii annellatus - from central and east Cambodia, and the south of Laos. Coat mainly reddish brown with a cream band near the base of the tail.
C. finlaysonii williamsoni - from Laos. Coat red to orange above, sharply demarcated from chestnut below, tail maroon.
C. finlaysonii boonsongi - from north-east Thailand. Coat mostly black or very dark, with white rim on ear and greater venter. Note a small proportion of creamy white and red individuals occur.
C. finlaysonii bocourtii (includes leucogaster, leucocephalus, floweri, tachardi, prachin, rajasima and cockerelli) - from central Thailand. Coat on dorsum black, rest including head white or cream, entirely cream in some peripheral populations.
C. finlaysonii sinistralis (includes dextralis, lylei and grulei) - from central to north-west Thailand. Coat mostly red but dorsum reddish agouti and a cream band on the tail.
C. finlaysonii menamicus - from north-central Thailand. Coat all red with buffy white tip to tail.
C. finlaysonii ferrugineus - from Burma. As C. finlaysonii menamicus but geographically isolated
C. finlaysonii finlaysonii - from Si Chang, Thailand. Coat all white, tinged yellow especially on back.
C. finlaysonii folletti - from Phai, Thailand. Coat white with grey hair bases showing.
C. finlaysonii trotteri - from Lan, Thailand. Coat grey with white tail and blackish feet.
C. finlaysonii frandseni - from Chang, Thailand. Coat red with grey flanks.
C. finlaysonii albivexilli - from Tut, Thailand. Coat black, but with white tip to tail. Thorington et al. (2012) gave Koh (= island) Kut as location.
C. finlaysonii harmandi (includes C. finlaysonii pierrei) - from Phu Quoc, Vietnam. Coat dark reddish brown above, light orange-red below, tail greyish white. Abramov et al. (2007) also notes that the fluffy, light gray tail has length white under-hairs.
C. finlaysonii germaini - from Condor I, Vietnam. Coat all black.
Similarities to Other Species/ConditionsTop of page
Corbet and Hill (1992) noted that ‘the species is so variable that no simple diagnosis applies.’ Across parts of its range it is sympatric with C. erythraeus and may be confused with this species. For example, C. finlyasonii sinistralis can only be distinguished from C. erythraeus atrodorsalis by the pale base of the tail. Moore and Tate (1965) provided a key to distinguish Callosciurus from other sympatric squirrel genera and describe the following characteristics:
- The least inter-orbital breadth exceeds the greatest length of the nasal bone.
- There are no pronounced longitudinal stripes on the back (although there may be on sides and venter)
- There is a single, unforked bony septum across the chamber of the auditory bulla.
- The 3rd upper molar is present.
- The coronoid process of the mandible is high and falcate.
- The upper edge of the infra-orbital foramen is well separated from the maxillo-premaxil-larysuture
- The baculum consists of two separate parts, a shaft and a blade.
- Orbit length exceeds 13 mm.
- The supra-orbital notches are obsolescent.
Callosciurus is distinguished from the other genera of squirrels of the Indian and Indochinese subregions by the above characters as follows: from Ratufa by 3, 4, 6 and 7; Funambulus by 2, 5 and 7; Tamiops by 2 and 8; and Dremonys by 1.
Prevention and ControlTop of page
C. finlaysonii is considered an invasive alien species where it has been introduced outside its natural range. Timmins and Duckworth (2008) alluded to an eradication plan for C. finlaysonii finlaysonii in Singapore, citing Lee BPY-H (in prep), but no further information could be found. In Italy, Bertolino and Genovesi (2005) discussed measures for C. finlaysonii control with respect to the wider European strategy on invasive alien species.
Tree squirrels can be highly successful invaders with only few individuals needed for successful establishment (e.g. Bertolino and Genovesi, 2005; Wood et al., 2007) and in many ways represent an alien species conundrum (Bertolino and Lurz, 2013). By the time small founder populations expand sufficiently and their behaviour (such as competition with native species, damage to trees and crops, and being a vector for disease or parasites) is considered a problem, it is often too late for effective control or eradication due to logistic, economic or political reasons. Squirrels have an innate appeal and are often fed by members of the public where they occur in urban or suburban areas. Experience in Italy (Bertolino S, pers. comm.) has shown that any management action needs to include monitoring (to assess distribution and effectiveness of management actions; see Gurnell et al. (2009) for methods), as well as measures to increase public awareness and understanding with respect to the economic and conservation problems and dangers of introduced invasive species.
Gaps in Knowledge/Research NeedsTop of page
There is a dearth of information with respect to ecology (e.g. function of species in ecosystem, potential role as disperser of seeds), behaviour (e.g. dispersal, mating, foraging), life history (mortality, fecundity), population dynamics in different habitat types, parasites and diseases (and potential as vector for zoonotic diseases), as well data on population trends for known subspecies across Myanmar, Thailand, Laos, Cambodia and Vietnam.
Given the huge variability in described forms, the reports of as yet unnamed forms (Evans et al., 2000; Timmins and Duckworth, 2008), and the suggestion of hybridisation with closely related Callosciurus species, a systematic, comprehensive review of this species using morphological and genetic approaches is highly desirable.
ReferencesTop of page
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Principal SourceTop of page
Draft datasheet under review
ContributorsTop of page
11/09/14 Original text by:
Peter Lurz, Royal School of Veterinary Studies, UK
Distribution MapsTop of page
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