Callosciurus finlaysoniiFinlayson's squirrel

Geographic Range

Finlayson's squirrels are native to central Indochina from central Myanmar southeast through much of Thailand, Lao PDR, and Cambodia to the Mekong Delta in South Vietnam. (Bertolino, et al., 2000; Duckworth, et al., 2008)

In addition, Finlayson's squirrels have been introduced to different locations. For example, this species has been introduced to towns in Italy. One pair of this species was introduced into Acqui Terme in the commune of Piedmont in northern Italy in 1982 and also in Maratea in the 1980's. In Asia, this species was introduced to Singapore, Hamamatsu, and Shizuoka. (Bertolino and Lurz, 2013)


Finlayson's squirrels are terrestrial and highly arboreal. They inhabit many forested habitats, such as dense forest, coconut plantations, and sparse woods. They are known from forested limestone mountains of central Lao PDR. Finlayson's squirrels spend most of their time in trees and are rarely seen on the ground. (Bertolino, et al., 2000; Duckworth, et al., 2008)

After the introduction into Maratea, the population expanded to colonize a narrow belt of woods by the Tyrrhenian coast. It is predicted that the next habitat that this species will take over is the deciduous forest adjacent to these coastal woods. (Bertolino and Aloise, 2005)

Physical Description

Coat color in Finlayson's squirrels varies according to subspecies and members within subspecies. The coat color may range from all white, to all red, to all black. Due to the variability of the coat color of this species, it is often referred to as variable squirrel. (Bertolino, et al., 2000; Thorington, 2012)

Males and females can be distinguished from each other by the external scrotum and testes on the male, and a vulva that appears as a dark dot on a white background on the female. Females can also be distinguished by 4 visible teats. (Bertolino, 2005)

On average, the head to body length of females is 191.8 mm. The average tail length in females is 172.8 mm. For males, the average head to body length is 190.1 mm, and average tail length is 173.4 mm. The average mass of adults (in both sexes) is 278.0 g. The average head to body length and tail length respectively in adults (in both sexes) is 212.1 mm and 222.0 mm respectively. (Thorington, 2012)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    278.0 g
    9.80 oz
  • Range length
    190.1 to 212.1 mm
    7.48 to 8.35 in


As a member of the family Sciuridae these squirrels have a polygyandrous mating system in which many males can mate with many females. Males will perform mating calls and mating chases as a part of mating rituals. (Bertolino, 2004; Bertolino, 2004; Brown, et al., 2012)

Finlayson's squirrels have three reproductive periods: April, July to August, and November to December. Females have only 1 to 2 offspring during each one of these reproduction periods, and females reach sexual maturity at about their 2nd year of life. (Bertolino, 2004)

Finlayson's squirrels have a high reproductive rate because sexual maturity is reached early and the females have a short gestational period. (Bertolino, 2004; Bertolino, 2005)

  • Breeding interval
    Breeding interval is not reported, but female squirrels are likely to have multiple litters per year.
  • Breeding season
    April, July to August, and November to December
  • Range number of offspring
    0 to 2
  • Average age at sexual or reproductive maturity (female)
    2 years

Finlayson's squirrels build nests from plant material to care for their young. Females care for the young. Further research is required to observe details of parental care in this species. (Bertolino, 2004; Brown, et al., 2012)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


Limited information is available for the lifespan of Finlayson's squirrels. In captivity, they are known to survive a maximum of 12.8 years. There is currently no record of the lifespan of the species in the wild. (Weigel, 2005)

  • Average lifespan
    Status: captivity
    12.8 years


Finlayson's squirrels spend from 75.9% to 96.3% of their time active, with a major proportion of that time spent foraging. (Bertolino, 2005)

Home Range

The home range has not been determined. (Bertolino, 2005; Duckworth, et al., 2008)

Communication and Perception

There have been 10 types of vocalizations identified in this species, in particular in the members that reside in Acqui Terme. They consist of alarm signals in the presence of cats and of magpies, male distant calling signals, male close calling signals, male courtship calls (made of three sequences of emissions with different intervals), mating calls, mother distant calls, young distant calls, and squeaks. It is likely that they also communicate with visual and chemical cues. (Bertolino, 2004)

Food Habits

Finlayson's squirrels spend a majority of their active time foraging. Their diet varies seasonally and regionally. For example, they will feed on bark and buds during the winter, flowers in the spring, and then mature seeds and fruit between June and October. In the summer, the squirrels will search for and eat insects. (Bertolino, 2004; Bertolino, 2005)

Finlayson's squirrels feed on a wide variety of trees. Since the majority of their time is spent in trees, they also spend the majority of their feeding time consuming tree matter. In Acqui Terme, these squirrels spend 36.5% of their feeding time consuming bark and sap, 36% seeds and fruits, 11.3% on buds and 6.5% on flowers. (Bertolino, 2004)

Finlayson's squirrels also cache food. In the urban park areas of Acqui Terme, this can be observed occasionally when the squirrels store hazelnuts, walnuts, and seeds given to them by visitors. They store food in nests or scatter them across trees. Their ability to adapt to a wide range of foods, active foraging skills, and hoarding behavior are key factors in their ability to survive outside of their native habitat. (Bertolino, 2004)

  • Animal Foods
  • insects
  • Plant Foods
  • wood, bark, or stems
  • seeds, grains, and nuts
  • sap or other plant fluids


In Acqui Terme, Finlayson's squirrels interacted with species such as magpies, hooded crows, and domestic cats. They would emit alarm calls when the magpies and crows approached their juveniles or when cats would approach a tree that they were at. Cats were unsuccessful as predators and only once was it observed that a cat followed a squirrel up a tree. Predators in their native range are not reported, but are likely to be arboreal predators, such as birds, cats, and snakes. (Bertolino, 2004)

Finlayson's squirrels mostly arboreal lifestyle is an adaptation related to competition and predator avoidance in its native territory in Indochina. (Bertolino, 2004)

Ecosystem Roles

As an invasive species, Finlayson's squirrels have a significant impact on native species where they have been introduced, including Italy and Japan. Since the diet is comprised of mainly plant matter, it strips many species of trees of its bark. In Acqui Terme Finlayson's squirrels stripped the bark off of 80% of the 10 species it found most palatable. In Maratea, the squirrels strip the bark off of these species of trees: Ceratonias iliqua, Quercus virgiliana, Quercus ilex, and Olea europea. Ecosystem roles in their native habitat are not reported, but may include seed dispersal and acting as an important prey source for arboreal predators. (Bertolino and Aloise, 2005; Bertolino, 2004; Bertolino, 2005)

Economic Importance for Humans: Positive

There have been no studies documenting positive effects of this species on economy. Members of this species are often sold as domestic pets, especially in Italy. (Bertolino, 2004)

Economic Importance for Humans: Negative

Finlayson's squirrels have a negative impact on the human economy because they destroy electric cables and other structures. More study is required to assess the full impact this species has on humans. (Bertolino, 2005)

Conservation Status

Finlayson's squirrels are categorized as Least Concern because of their wide distribution and ability to adapt to a wide range of environments. (Bertolino, 2005; Duckworth, et al., 2008)

Other Comments

Finlayson's squirrels are also called variable squirrels because of their wide range in coat color. (Thorington, 2012)


Luqian Liu (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Tanya Dewey (editor), University of Michigan-Ann Arbor.



living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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uses sound to communicate


living in landscapes dominated by human agriculture.


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate

  1. active during the day, 2. lasting for one day.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females


an animal that mainly eats leaves.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly plants or parts of plants.


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


found in the oriental region of the world. In other words, India and southeast Asia.

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pet trade

the business of buying and selling animals for people to keep in their homes as pets.


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


living in cities and large towns, landscapes dominated by human structures and activity.


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Bertolino, S. 2004. Activity Budget and Foraging Behavior of Introduced Callosciurus Finlaysonii (Rodentia, Sciuridae) in Italy. Journal of mammalogy, 85: 254 - 259.

Bertolino, S. 2005. The Application of the European Strategy on Invasive Alien Species: An Example with Introduced Squirrels. Hystrix Italian Journal of Mammalogy, 16: 59-69. Accessed March 06, 2014 at

Bertolino, S., G. Aloise. 2005. Free-Ranging Populations of the Finlayson's Squirrel Callosciurus Finlaysonii (Horsfield,1824)(Rodential, Sciuridae) In South Italy. Hystrix Italian Journal of Mammalogy, 16 (1): 70-74.

Bertolino, S., I. Currado, P. Mazzoglio, G. Amori. 2000. Native and Alien Species of Squirrels in Italy. Hystrix Italian Journal of Mammalogy, 11.2: 65-74.

Bertolino, S., P. Lurz. 2013. Callosciurus squirrels: worldwide introductions, ecological impacts and recommendations to prevent the establishment of new invasive populations.. Mammal Review, 43: 22-33.

Brown, E., Squirrel Girls, A. Peri, N. Santarosa. 2012. "Sciuridae squirrels" (On-line). Animal Diversity Web. Accessed April 12, 2014 at

Duckworth, J., R. Timmins, M. Parr. 2008. "IUCN Red List of Threatened Species" (On-line). Accessed March 06, 2014 at

Thorington, R. 2012. Squirrels of the World. Baltimore, MD: Johns Hopkins University Press.

Weigel, R. 2005.

Longevity of Mammals in Captivity; from the Living Collections of the World
. Stuttgart: Kleine Senckenberg-Reihe 48.