Douglas squirrel

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Douglas squirrel

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Genus: Tamiasciurus
Species:
T. douglasii
Binomial name
Tamiasciurus douglasii
(Bachman, 1839)[2]
Subspecies[3]
Range (does not include T. d. mearnsi)

The Douglas squirrel (Tamiasciurus douglasii) is a

alarm call.[4]

Description

Sciuridæ
". Adults are about 33 cm in length (including its tail, which is about 13 cm long), and weigh between 150 and 300 grams. Their appearance varies according to the season. In the summer, they are greyish or almost greenish-brown on their backs, and pale orange on the chest and belly, while legs and feet appear brown. In the winter, the coat is browner and the underside is grayer; also, the ears appear even tuftier than they do in summer. Like many squirrels, Douglas squirrels have a white eye-ring.

Anacortes Community Forest Lands (Washington)

Breeding

Mating can occur as early as February. Gestation is about four weeks, and the young (which are

altricial
) are weaned at about eight weeks of age. There may be up to six kits in a litter, though four is more usual. In the southern and lower parts of their range, they produce two litters each year.

Habitat

Douglas squirrels live in

Sierra Nevada (mountains) of California, northwards to the southwestern coast of British Columbia. Tamiasciurus douglasii prefer old-growth forests or mature second-growth forests, and some authors regard them as dependent on its presence. Mearns's squirrel is a distinctive subspecies of the Douglas squirrel that instead inhabits xeric pine forests in a small portion of Baja California.[5]

Throughout most their range, Douglas squirrels essentially replace the niche of the American red squirrel, which inhabits the coniferous forests of the rest of North America. The two species have very minimal overlap in the territory.

Douglas squirrels are territorial; in winter, each squirrel occupies a territory of about 10 000 square metres, but during the breeding season a mated pair will defend a single territory together. Douglas squirrels are active by day, throughout the year, often chattering noisily at intruders. On summer nights, they sleep in ball-shaped nests that they make in the trees, but in the winter they use holes in trees as nests. Groups of squirrels seen together during the summer are likely to be juveniles from a single litter.

Diet

Douglas squirrels mostly eat seeds of coniferous trees such as

giant sequoia cones, as well as acorns, berries, mushrooms, the eggs of birds such as yellow warblers, and some fruit including strawberries and plums. Douglas squirrels are larder hoarders,[6] storing their food in a single location or 'larder' called a midden
. As the squirrel peels the scales of cones to get at the seeds, the discarded scales accumulate into piles that can grow to several meters across as the same site is used by generations of squirrels.

Their predators include Pacific martens, bobcats, domestic cats, northern goshawks, and owls; although they quickly acclimatize to human presence, humans can be a threat to them, through robbing of their cone caches to find seeds for tree cultivation and through the destruction of old-growth forest. However, the squirrels' numbers appear to be unaffected by commercial thinning of forests.[7]

Pacific silver fir cone debris from Douglas squirrels feeding, North Cascades National Park
Tamiasciurus douglasii alarm call
Alarm call of the Douglas squirrel (Tamiasciurus douglasii)
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References

  1. ^ Linzey, A. V. & Hammerson, G. (2008). "Tamiasciurus douglasii". IUCN Red List of Threatened Species. 2008. Retrieved 8 January 2009.
  2. ^ Bachman, J. (1839) Archived January 7, 2009, at the Wayback Machine. Description of several new Species of American quadrupeds. Journal of the Academy of Natural Sciences of Philadelphia, 8, 57-74.
  3. OCLC 26158608
    .
  4. ISBN 0-87156-663-X
    .
  5. PMID 27083861
    .
  6. ^ "Gray squirrels and scatter hoarding". 24 September 2013. Retrieved 2015-11-20.
  7. doi:10.1139/x02-126
    .

External links

Wikimedia Commons has media related to Tamiasciurus douglasii.
Wikispecies has information related to Tamiasciurus douglasii.
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