The Douglas squirrel (''Tamiasciurus douglasii'') is a
pine squirrel
Pine squirrels are squirrels of the genus ''Tamiasciurus'', in the Sciurini tribe, of the large family Sciuridae.
Species
This genus includes three species:
*''Tamiasciurus hudsonicus'' — American red squirrel
*''Tamiasciurus douglasii'' ...
found in the
Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
of North America, including the northwestern coastal states of the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
as well as the southwestern coast of
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
in
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, with an isolated subspecies in northern
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
. It is sometimes known as the chickaree or pine squirrel, although these names are also used for the
American red squirrel
The American red squirrel (''Tamiasciurus hudsonicus'') is one of three species of tree squirrels currently classified in the genus ''Tamiasciurus'', known as the pine squirrels (the others are the Douglas squirrel, ''T. douglasii'', and the sou ...
.
Variant spellings
Spelling is a set of conventions that regulate the way of using graphemes (writing system) to represent a language in its written form. In other words, spelling is the rendering of speech sound (phoneme) into writing (grapheme). Spelling is one ...
of the
common name
In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
are Douglas' squirrel and Douglas's squirrel. The
Native Americans of
Kings River called it the "Pillillooeet", in imitation of its characteristic
alarm call
In animal communication, an alarm signal is an antipredator adaptation in the form of signals emitted by social animals in response to danger. Many primates and birds have elaborate alarm calls for warning conspecifics of approaching predators ...
.
Description
John Muir
John Muir ( ; April 21, 1838December 24, 1914), also known as "John of the Mountains" and "Father of the National Parks", was an influential Scottish-American naturalist, author, environmental philosopher, botanist, zoologist, glaciologist, a ...
described the Douglas squirrel, ''Tamiasciurus douglasii'', as "by far the most interesting and influential of the California
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.
Breeding
Mating can occur as early as February. Gestation is about four weeks, and the young (which are
altricial
In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...
) 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
coniferous
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extant ...
forest
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
s along the Pacific Coast, from the
Sierra Nevada
The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...
(mountains) of
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
, northwards to the southwestern coast of
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
. ''Tamiasciurus douglasii'' prefer
old-growth forest
An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological featur ...
s or mature second-growth forests, and some authors regard them as dependent on its presence.
Mearns's squirrel
Mearns's squirrel (''Tamiasciurus douglasii mearnsi'') is a subspecies of the Douglas squirrel Endemism, endemic to Mexico. It is endangered species, endangered and occurs in low densities, and is threatened by habitat loss.Koprowski, Ramos, Pasc ...
is a distinctive subspecies of the Douglas squirrel that instead inhabits
xeric
Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (ancient Greek xērós, “dry") shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this h ...
pine forests in a small portion of
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
.
Throughout most their range, Douglas squirrels essentially replace the
American Red Squirrel
The American red squirrel (''Tamiasciurus hudsonicus'') is one of three species of tree squirrels currently classified in the genus ''Tamiasciurus'', known as the pine squirrels (the others are the Douglas squirrel, ''T. douglasii'', and the sou ...
, which inhabits the coniferous forests of the rest of North America, in these areas. 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
Douglas fir (''Pseudotsuga menziesii''),
Sitka spruce (''Picea sitchensis'') and
shore pine (''Pinus contorta''). They also eat the fleshy scales of green
giant sequoia
''Sequoiadendron giganteum'' (giant sequoia; also known as giant redwood, Sierra redwood, Sierran redwood, California big tree, Wellingtonia or simply big treea nickname also used by John Muir) is the sole living species in the genus ''Sequoiade ...
cones, as well as acorns, berries, mushrooms, the eggs of birds such as
yellow warbler
The yellow warbler (''Setophaga petechia'') is a New World warbler species. Yellow warblers are the most widespread species in the diverse genus ''Setophaga'', breeding in almost the whole of North America, the Caribbean, and down to northern S ...
s, and some fruit including strawberries and plums. Douglas squirrels are
larder
A larder is a cool area for storing food prior to use. Originally, it was where raw meat was larded—covered in fat—to be preserved. By the 18th century, the term had expanded. Now a dry larder was where bread, pastry, milk, butter, or cooked m ...
hoarders, storing their food in a single location or 'larder' called a
midden
A midden (also kitchen midden or shell heap) is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, mollusc shells, potsherds, lithics (especially debitage), and other artifacts and ecofact ...
. 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
American marten
The American marten (''Martes americana''), also known as the American pine marten, is a species of North American mammal, a member of the family Mustelidae. The species is sometimes referred to as simply the pine marten. The name "pine marten" ...
s,
Bobcat
The bobcat (''Lynx rufus''), also known as the red lynx, is a medium-sized cat native to North America. It ranges from southern Canada through most of the contiguous United States to Oaxaca in Mexico. It is listed as Least Concern on the IUC ...
s,
domestic cats
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of t ...
,
northern goshawk
The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
s, and
owl
Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...
s; 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.
[Ransome, D. B., & Sullivan, T. P. (2002). Short-term population dynamics of ''Glaucomys sabrinus'' and ''Tamiasciurus douglasii'' in commercially thinned and unthinned stands of coastal coniferous forest. Canadian Journal of Forest Research, 32, 2043-2050.]
References
External links
Tracks and calls of the Douglas SquirrelSmithsonian: "The Douglas Squirrel"
{{Authority control
Tamiasciurus
Mammals of the United States
Mammals of Canada
Fauna of the Sierra Nevada (United States)
Fauna of the Western United States
Fauna of the Northwestern United States
Mammals described in 1839
Taxa named by John Bachman