Tamiasciurus hudsonicus

73.

North American Red Squirrel

Tamiasciurus hudsonicus

French: Ecureuil roux / German: Rothérnchen / Spanish: Ardilla roja de Norteamérica

Other common names: Pine Squirrel

Taxonomy. Sciurus hudsonicus Erxleben, 1777,

“ad fretum Hudsonis.”

Restricted by

A. H. Howell in 1936 to the mouth of Sev-

ern River, Hudson Bay, Ontario, Canada.

Genetic data suggest that subspecies of 1. hudsonicus may not be well supported. Twenty-one subspecies recognized.

Subspecies and Distribution.

T.h.hudsonicusErxleben,1777—ESaskatchewan,Manitoba,andOntario(Canada),NMinnesotaandMichigan(USA).

T.h.abieticolaA.H.Howell,1929—SouthernAppalachianMtsinSEUSA.

T.h.baileyi].A.Allen,1898—NCMontanatoSCWyoming(USA).

T.h.columbiensisA.H.Howell,1936—SYukontoCBritishColumbiaandSWAlberta(Canada).

T.h.dakotensis].A.Allen,1894—SEMontana,NEWyoming,andWSouthDakota(USA).

T.h.dixiensisHardy,1942—SWUtah(USA).

T.h.gymnicusBangs,1899—Vermont,NewHampshire,andMaine(USA)andalongSt.LawrenceRivertoNovaScotia(Canada).

T.h.kenaiensisA.H.Howell,1936—KenaiPeninsula,SAlaska(USA).

T.h.lanuginosusBachman,1839—ScoastalSEAlaska(USA)andBritishColumbiaincludingVancouverI(Canada).

T.h.laurentianusR.M.Anderson,1942—SEQuebec(Canada).

T.h.loquaxBangs,1896—SEOntarioandSWQuebec(Canada),andfromMichiganandIndianaEtoNewYorkandStoNVirginia(USA).

T.h.minnesotaJ.A.Allen,1899—NCUSA,fromENorthDakotaandNESouthDakotatoWisconsin,Iowa,andNIllinois.

T.h.pallescensAH.Howell,1942—SManitoba(Canada)andNorthDakota(USA).

T.h.petulansOsgood,1900—NcoastalSEAlaska(USA)andSWYukon(Canada).

T.h.picatusSwarth,1921—CcoastalSEAlaska(USA)andcontiguousBritishColumbia(Canada).

T.h.prebleiAH.Howell,1936—mostofAlaska(USA)andNW&CCanada.

T.h.regalisA.H.Howell,1936—IsleRoyaleinLakeSuperior,USA.

T.h.richardsoniBachman,1839—SEBritishColumbia(Canada),WMontana,CIdaho,andWOregon(USA).

T.h.streatoriJ.A.Allen,1898—SBritishColumbia(Canada),EWashingtonandNIdaho(USA).

T.h.ungavensisR.M.Anderson,1942—NQuébecandNewfoundlandandLabradorinNECanada.

T. h. ventorumJ. A. Allen, 1898 — SW Montana, NW Wyoming, S E Idaho, and N Utah (USA).

Descriptive notes. Head-body mean 187 mm (males) and 189-7 mm (females), tail mean 123-7 mm (males) and 123-6 mm (females); weight mean 194 g (males) and 213 g (females). The North American Red Squirrel has reddish to ferruginous brown to olivaceous gray dorsal pelage, with reddish medial band that is especially apparent in grayish forms. Venter is white to grayish and is separated from dorsum by charcoal to black longitudinal stripe. White to buff eye ring is usually prominent, with white to buff at snout and chin. In winter, ears can have black tuft and postauricular white to buff patches. Tail is similar in color to dorsum, with ventral side often most reddish and frosted with white to cream. Bright reddish forms are abieticola, gymnicus, hudsonicus, lawrentianus, loqguax, minnesota, preblei, and ungavensis. Brownish or olivaceous subspecies are baileyi, columbiensis, dakotensis, dixienss, lanuginosus, pallescens, petulans, picatus, richardsoni, streatori, and ventorum. Subspecies regalis and kenaiensis are geographically isolated. Chromosome numberis 2n = 46.

Habitat. Deciduous and coniferous forests. In northern, western, and high-elevation parts of the distribution, boreal coniferous forests with considerable pine (Pinus), fir (Pseudotsuga and Abies), spruce (Picea), and hemlock (7suga), all Pinaceae with closed canopies are most favored. North American Red Squirrels use open parkland forests in some areas. In the eastern distribution, they also occupy mixed coniferous-deciduous forests and hardwood forests with scattered conifers. The North American Red Squirrel can be found in urban parks, suburban areas with mature trees, and secondary growth forests.

Food and Feeding. The North American Red Squirrel is primarily granivorous but also can be opportunistically omnivorous. Primary foods include seeds of conifers, oak

(Quercus) and beech (Fagus), both Fagaceae; hickory (Carya) and walnut (Juglans), both Juglandaceae; and maple (Acer, Sapindaceae). Epigeous and hypogeous mycorrhizal fungi are also commonly eaten. Supplementary planttissues are eaten, including tree buds and flowers, fruits, and phloem. When encountered, the North American Red Squirrel will feed on insects, bones, scavenged carcasses, eggs, avian nestlings, and other animal material. It hoards food, primarily conifer cones, in a larder (midden) located near the center of a home range near large trees, dense understory, and fallen logs. In deciduous forests, the North American Red Squirrel scatterhoards seeds and buries them just under the surface. A midden is crucial for overwinter survival because it permits storage of conifer cones in cool moist environments to maintain conifer seeds. Individuals pilfer cones from caches of neighbors and other species are attracted to middens for potential food and cover. Fungi, especially hypogeous truffles, are eaten heavily in summer and are often cached in tree branches and cavities.

Breeding. The North American Red Squirrel nests in leaf and twig dreys, cavities in trees, or occasionally in burrows in which young are born. Females ovulate spontaneously and are in estrus for only one day during breeding season. Mating bouts that involve several males chasing a female and with copulations by multiple males. Gestation averages 33 days, and litter sizes average 3-2-5-4 young. North American Red Squirrels typically produce only one litter per year, but females can produce two litters per year, especially in the eastern part of the distribution. Young leave the nest by c.7 weeks of age; they are weaned at c.14 weeks and are independent a few weeks after weaning. Most young disperse from their natal areas at this time, although in some populations, dispersal can be male-biased, and individuals can move more than 1 km before they settle.

Activity patterns. North American Red Squirrels are diurnal, with midday peak in activity in winter and bimodal activity pattern in spring and summer. It remains active throughout the year but can enter torpor for short bouts of several days during extreme weather events.

Movements, Home range and Social organization. The North American Red Squirrel is generally asocial. In coniferous forests where cones are stored in middens, the North American Red Squirrel is fiercely territorial and maintains exclusive use of a territory that is usually less than 1 ha. Although most young disperse from natal areas, young sometimes inherit territories of their mothers after weaning. Densities are 0-5-2 ind/ ha in most habitats. In areas where North American Red Squirrels do not maintain middens, such as deciduous and mixed forests, overlapping home ranges are common. Minimal sex differences in space use have been reported. Most interactions are agonistic and consist of vocalizations and foot stomping, followed by chasing and rarely combat. Adults sometimes nest together in winter. Alarm calls can be high-pitched whines followed by a series of chatters or chucks. A loud territorial call known as the rattle reverberates through the forest, especially in autumn when food resources are stockpiled. Movement is impeded by forest openings.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Population trend of the North American Red Squirrelis stable. It responds negatively to forest fragmentation and clear cutting, but its substantial distribution likely ensures persistence. North American Red Squirrels can damage trees by bark stripping and girdling trees to consume phloem and cambium.

Bibliography. Benkman & Siepielski (2004), Berteaux & Boutin (2000), Bertolino (2009), Boon et al. (2007, 2008), Boutin et al. (2006), Descamps et al. (2006), Howell (1936b), Kemp & Keith (1970), Lane et al. (2008), Larsen & Boutin (1994, 1995), Layne (1954), McAdam & Boutin (2003), McAdam et al. (2007), Price et al. (1986), Rusch & Reeder (1978), Smith (1965, 1968, 1970, 1978, 1981), Steele (1998), Thorington et al. (2012), Wheatley et al. (2002).