Taxonomy

Callosciurus erythraeus | Pallas's squirrel

Distribution

Status

Legal status

Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].

Invasiveness

Invasive species - risk of High Impact

Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Botanical garden/zoo/aquaria, Pet/aquarium species

Introduction pathways - 2

Release in Nature

Introduction pathways subclass - 2

Other intentional release

Invasive score

18

NAPRA Ireland risk assessed

No

Species Biology

Identification

Diurnal arboreal squirrel of similar size to Red squirrel (Sciurus vulgaris) (NNSS, 2016). No sexual dimorphism (Lurz et al., 2016). Head body length is 20-26cm and tail length is 16-20cm (Schockert, 2012). There is variation in colour forms but body colour is usually olive-brown agouti with lighter chin, neck, legs and feet. The chest and abdomen are chestnut or mahogany red. The tail is bushy with some white tipped hairs (NNSS, 2016). The call is a dog-like bark.

Ecology

Can establish a successful population from just a few founder animals (Stockert, 2012). They are highly adaptable in terms of food sources and nest sites. They have a high reproductive capacity and can disperse readily (UNEP-WCMC, 2010). Eat leaves, seeds, flowers, fruits, buds and bark of several plant species as well as a small proportion of insects, snails and birds’ eggs (Tamura, 2009).

Its presence in large numbers may have an impact on native snail and bird species. Most active at dawn and dusk (NNSS, 2016). They compete with native Red squirrel (Sciurus vulgaris) for food and nest sites (Tamura, 2009). Can cause problems by cutting through phone and electricity wires (Tamura, 2009). They also strip bark from trees, damaging timber and killing trees, impoverishing species diversity in forestry and natural woodlands (Tamura, 2009).

Reproduction

Builds nests or uses tree hollows in the 'mid-high canopy of trees' (Schockert, 2012). Breed throughout the year with 1-3 litters per year per female (Tamura, 2009). Gestation period is 47-49 days (Schockert, 2012). Litters usually contain 1-2 young (NNSS, 2016) with an average of 1.4 surviving to weaning age (Schockert, 2012). Each female may breed with 4 different males (NNSS, 2016). Males and females reach maturity at younger than 1 year and may live for 5 years (Tamura, 2009).

Pathway and vector description

Have been introduced by escapes from zoos or through deliberate introductions for ornamental purpose (NNSS, 2016) or through the pet trade (Tamura, 2009). They are readily available to purchase online (UNEP-WCMC, 2010).

Mechanism of impact

Competition, Predation, Other

Management approach

No effective predators in its introduced range (Tamura, 2009). Early detection is the single biggest obstacle as populations may be well established before they are noticed (Stuyck et al., 2009). Eradication is possible but action must be taken as early as possible once an invasion has been detected (Stuyck et al., 2009).

Public awareness

Public awareness campaigns relating to identification, regulations and threats posed by this species would aid in early detection.

Live trapping

Schtockert (2012) describes the eradication of a population in Belgium using live trapping. Should be carried out from September to December as Sciurus vulgaris rears its young from January to September. Useful bait is banana or walnuts or peanuts. Traps should be checked twice a day. The animals are then either euthanised with carbon dioxide gas or sterilised and exported to zoos. The use of sterilisation rather than euthanasia in the Netherlands encouraged the general public to get involved in the trapping (Schtockert, 2012).

Broad environment

Terrestrial

Habitat description

Prefers mixed forest but can be found in evergreen forestry, woodland, orchards and parks. Female range is approximately 0.5ha and the male range approximately 2ha (Tamura, 2009).

Species group

Vertebrate

Native region

Tropical Asia

Similar species

Sciurus vulgaris can be distinguished by its white belly and distinctive ear tufts (Schockert, 2012).

Distribution

World distribution(GBIF)

Introduced in Japan, Hong Kong, Argentina, France, Belgium, the Netherlands, Italy.

Native distribution

From Bhutan and Assam to Taiwan and the Malay Peninsula (NNSS, 2016).

Temporal change

Records submitted to Data Centre in 2021

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Do not purchase as a pet.

Report any sightings to the National Biodiversity Data Centre.

References

Publications

GB Non-native Species Secretariat (NNSS) (2016) Pallas's squirrel Callosciurus erythraeus. Factsheet. NNSS. http://www.nonnativespecies.org/factsheet/downloadFactsheet.cfm?speciesId=4363 Site accessed 26 September 2017.

Lurz, PWW; Hayssen, V; Geissler, K; Bertolino, S (2013) Callosciurus erythraeus (Rodentia: Sciuridae), Mammalian Species, 45 (902), Pp 60–74, https://doi.org/10.1644/902.1 Site accessed 26 September 2017.

Schockert, V. (2012) Risk analysis of the Pallas's squirrel, Callosciurus erythraeus, Risk analysis report of non-native organisms in Belgium.Cellule interdépartementale sur les Espèces invasives (CiEi), DGO3, SPW / Editions, 39 pages http://ias.biodiversity.be/species/show/126 Site accessed 26 September 2017.

Stuyck, J., Baert, K., Breyne, P. & Adriaens, T. (2009) Invasion history and control of a Pallas squirrel Callosciurus erythraeus population in Dadizele, Belgium. Proceedings of the Science facing Aliens conference, Brussels, 11th May 2009.

Tamura, N (2009) Invasive Species Compendium. Datasheet report for Callosciurus erythraeus (Pallas's squirrel). Wallingford, UK: CAB International. http://www.cabi.org Site accessed 26 September 2017.

UNEP-WCMC (2010) Review of Callosciurus erythraeus and Sciurus niger. UNEP-WCMC, Cambridge. http://ec.europa.eu/environment/cites/pdf/reports/Callosciurus_erythraeus_Sciurus_niger.pdf Site accessed 26 September 2017.

Animal Diversity Web

DAISIE Factsheet

IUCN Red List

Invasive Species in Belgium - Species information, documents and references

United Nations Environment Programme - World Conservation Monitoring Centre. Review of Callosciurus carolinensis and Sciurus niger



Additional comments

A population in Dadizele, Belgium has been successfully eradicated (Stuyck et al., 2009).

Images