The Sonoma chipmunk (''Neotamias sonomae'') is a species of

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

in the squirrel family

Sciuridae Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to northwestern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

in 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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

. Members of

Neotamias ''Neotamias'' is a genus of chipmunks within the tribe Marmotini of the squirrel family. It contains 23 species, which mostly occur in western North America. Along with ''Eutamias'', this genus is often considered a subgenus of ''Tamias''. Spe ...

are characterized by having 2 premolars. ''N. sonomae'' has 2 subspecies: ''N. s. alleni'' and ''N. s. sonomae''.

Distribution

The Sonoma chipmunk is only found in

, north of the

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water f ...

. Most of its range is within Sonoma and Marin counties.

Habitat

Sonoma chipmunks are found in areas of

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranea ...

. They can be found in

s of sticky laurel,

Ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine is a very large pine tree species of variable habitat native to mountainous regions of western North America. It is the ...

Douglas fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three v ...

spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfam ...

redwood Sequoioideae, popularly known as redwoods, is a subfamily of coniferous trees within the family Cupressaceae. It includes the largest and tallest trees in the world. Description The three redwood subfamily genera are '' Sequoia'' from coasta ...

, and black oak. They are generally associated with

coniferous forests 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 exta ...

. The

that Sonoma chipmunks inhabit is characterized by sagebrush plains. Sonoma chipmunks are found in

elevation The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § ...

s from 0 to 1800 m. These chipmunks typically live on the ground and make

burrow An Eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of s ...

s in the ground, but they can climb and may make

nest A nest is a structure built for certain animals to hold eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of organic materi ...

s in trees.

Physical characteristics

The Sonoma chipmunk has a total body length (including

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammal ...

) ranging from 220-264mm.

Tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammal ...

length ranges from 100-126mm, hind foot (pes) length is 34-39mm, and ear flap (pinna) length is 15-19mm. These chipmunks have 5 black/brown stripes running the length of their body with white stripes in between. The rest of the dorsal and ventral parts of the body range from tawny to cinnamon to gray. The

is edged in white. The belly is grayish white. Sonoma chipmunks have 2 molts per year, having a summer and winter

pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket ...

. The winter

is generally slightly darker and duller than the summer

. ''N. s. alleni'' is smaller and darker than ''N. s. sonomae''. There is no distinct

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

. There are 2 other species of chipmunks found in the geographic range of the Sonoma chipmunk: the

yellow-pine chipmunk The yellow-pine chipmunk (''Neotamias amoenus'') is a species of order Rodentia in the family Sciuridae. It is found in western North America: parts of Canada and the United States. These chipmunks are normally found in brush-covered areas, and ...

and the Townsend's chipmunk. The yellow-pine chipmunk will be smaller and less reddish than ''N. sonomae'' and will lack a white-edged tail. ''N. sonomae'' can be distinguished from the Townsend's chipmunk by having longer ears, tail, and legs, being paler, and having a bushier

. The

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

s of Sonoma chipmunks have the distinct post orbital process that is found in all sciurids. The

has a deep

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

, a long

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

, and small

incisive foramina In the human mouth, the incisive foramen (also known as: "''anterior palatine foramen''", or "''nasopalatine foramen''") is the opening of the incisive canals on the hard palate immediately behind the incisor teeth. It gives passage to blood vesse ...

. The

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s are curved and pincer-like, and the

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

are simple and

cuspidate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

. The

dental formula Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolog ...

for ''N. sonomae'' is .

Diet and behavior

Sonoma chipmunks typically forage on the ground or climb along small branches in brush. They eat

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...

herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicina ...

s, buds of

woody plant A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to herbaceous plants that die back to the ground until sp ...

s, as well as

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

s and

bird egg Bird eggs are laid by the females and range in quantity from one (as in condors) to up to seventeen (the grey partridge). Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been fertilized; it ...

s. Food is collected in their

cheek pouch Cheek pouches are pockets on both sides of the head of some mammals between the jaw and the cheek. They can be found on mammals including the platypus, some rodents, and most monkeys, as well as the marsupial koala. The cheek pouches of chipmunks ...

es and stored in their

s. These chipmunks will find elevated places to eat and rest so they can watch the surrounding area for

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...

s. Sonoma chipmunks have high-pitched, bird-like alarm calls that are distinct from other chipmunks and are emitted in response to potential threats. Females are usually the ones to make alarm calls. These alarm calls likely

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variati ...

due to

kin selection Kin selection is the evolutionary strategy that favours the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin altruism can look like altruistic behaviour whose evolution ...

, as the chipmunks nearby that hear the alarm calls are typically related to the individual making the

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 predato ...

. When an

is heard, the chipmunk will quickly move along a direct path to a covered, protected area and become still. These chipmunks undergo

torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...

winter Winter is the coldest season of the year in polar and temperate climates. It occurs after autumn and before spring. The tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultur ...

but arise periodically to eat from their food cache, since they do not accumulate fat stores.

Reproduction

Sonoma chipmunks

breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slig ...

once per year, anywhere from February to July, but most often in April to May. There is occasionally a second

breeding season Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...

for females if their first litter is lost.

Gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pr ...

lasts for 28–36 days. 3-5 young are produced per litter, but it is usually 4. The babies are

weaned Weaning is the process of gradually introducing an infant human or another mammal to what will be its adult diet while withdrawing the supply of its mother's milk. The process takes place only in mammals, as only mammals produce milk. The infan ...

after approximately 3 weeks, and the mother stops associating with them after they are

. The juveniles stay together for a few more weeks after their mother leaves. After this, the juveniles disperse. Males disperse in a larger range than females. Juveniles reach

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...

within one year, and the lifespan of these chipmunks is around 64 months. Females have higher survivorship and live longer than males. There is a 1:1 ratio of males to females when the juveniles disperse in spring. By the end of the year, this ratio favors females due to the higher risk of mortality in the wider ranging males. However, the ratio again becomes 1:1 by the fall of their second year of life, as first-year adult females have a high risk of mortality during their first breeding attempt. Over time, the ratio will once again favor females.

References

External links

{{Taxonbar, from1=Q24662792, from2=Q517630 Neotamias Endemic fauna of California Mammals of the United States Chipmunk, Panamint Fauna of the San Francisco Bay Area Natural history of the California Coast Ranges Natural history of Sonoma County, California Mammals described in 1915 Taxa named by Joseph Grinnell Taxonomy articles created by Polbot