Tamias siskiyouSiskiyou chipmunk

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Geographic Range

Siskiyou chipmunks (Tamias siskiyou) are found in central to southern Oregon and northern California, near the Pacific coast. Their geographic range is limited by natural barriers such as the Klamath River in Del Norte County, California and the Rogue River in Josephine County, Oregon. Likewise, the Siskiyou, Marble, South Fork and western Cascade Mountains also limit their geographic range. These barriers mark a dividing line between this species and similar chipmunks, such as Townsend's chipmunks. (McIntire, 1984; Sutton and Patterson, 2000)

Habitat

Siskiyou chipmunks are found in habitats with maritime climates involving wet winters with heavy snow accumulation and dry summers. These chipmunks live in mature forests of sugar and Jeffrey pines, incense cedars and Douglas fir trees. Areas that have been logged provide the benefit of stumps, logs and piles of coarse, woody debris for shelter and nesting. They make their homes in hollow trees, under fallen logs and in piles of leaves and wood. However, Siskiyou chipmunks are found mainly in dense forests, due to the canopy of conifer trees. These animals prefer upland habitats and are often found far from streams. However, if the area near a stream is heavily grazed by livestock, their habitation is more likely. The geologic formation of their habitat is primarily sandstone and limestone. (Johnston and Anthony, 2008; Sutton and Patterson, 2000)

  • Range elevation
    150 to 2400 m
    492.13 to 7874.02 ft

Physical Description

Among Siskiyou chipmunks, geographic variation is exhibited in both size and color, resulting in two subspecies. The inland and costal variations are distinguished primarily through cranial measurements and pelage differences. This variation is the product of an abrupt habitat change at the margin of the coastal forest, roughly 32 km inland. This geographic coloration difference is seen in neighboring species of chipmunks as well, indicating a possible adaptive reaction to environmental conditions. (Sutton and Patterson, 2000)

The subspecies Tamias siskiyou humboldti is found from the coast to about 32 km inland. Their coloration is darker and browner than their inland neighbors and they have lighter stripes. This subspecies also has dark lateral stripes that do not extend to the rump or ears. Behind the ears, they have pale gray patches. The undersides of this subspecies are gray, with pink or cinnamon. This subspecies also has larger cranial measurements. While the inland population, Tamias siskiyou siskiyou, is light brown with pale gray and creamy white undersides. Their rump and thighs are a dark, smoky color. They have a dark patch behind their eyes and a whitish patch behind their ears. These mammals have dark body stripes on their light, tawny brown and pale gray coat. Two sayal brown facial stripes distinguish it from Allen's chipmunks when paired with the grayish cinnamon inner body stripes and it is less gray than Townsend's chipmunks. (Sutton and Patterson, 2000)

Seasonal variation is also seen in both subspecies. Tamias siskiyou humboldti molts in June to produce a tawnier, cinnamon pelage with paler stripes. A second molt occurs in August or September that results in a thicker, darker olive color, with pale gray stripes. Tamias siskiyou siskiyou gradually becomes more brightly colored after the spring breeding season through the summer months. During September to November, these chipmunks develop darker, denser and duller pelage in preparation for winter. Sexual dimorphism is present in the lengths of their hind feet, mandibular toothrow and mandible in both subspecies, in each length, females are larger. Sexual characteristics and measurements can be used to distinguish between Siskiyou chipmunks and related species. Their baculum is unique due to its short, dorsoventrally thick shaft, broad base, small, distinct keel and slender tip, which is longer than the shaft. The baubellum is also atypical, with a dorsoventrally wide and laterally narrow base. The baubellum is nearly equal in length to the male shaft; the tips are thick, with small keels and narrow, lateral shelves. (Sutton and Patterson, 2000)

  • Sexual Dimorphism
  • female larger
  • Range mass
    65 to 85 g
    2.29 to 3.00 oz
  • Range length
    250 to 268 mm
    9.84 to 10.55 in

Reproduction

Siskiyou chipmunks mate in the spring after emerging from hibernation, this occurs in mid-April for lower elevations and a few weeks later in higher elevations. These animals appear to have a promiscuous mating system. (Sutton and Patterson, 2000)

Siskiyou chipmunks breed once a year, typically resulting in 4 to 6 offspring after about a 28 week gestation period. The offspring remain in nests located in trees or in grass and moss-lined burrows, they are fed by their lactating mother for at least a few weeks. (; Sutton and Patterson, 2000)

  • Breeding interval
    Siskiyou chipmunks breed once each year.
  • Breeding season
    Siskiyou chipmunks breed after emerging from hibernation, this occurs in mid-April in lower elevations and a few weeks later in higher elevations.
  • Range number of offspring
    4 to 6
  • Average gestation period
    28 days
  • Range weaning age
    3 to 4 weeks

Among Siskiyou chipmunks, most births occur in May and June. Many females collected in June and July were lactating, which indicates that females care for their offspring for several weeks or months. (Sutton and Patterson, 2000)

Lifespan/Longevity

Little is known about the lifespan of these mammals as they are not typically kept in captivity or studied across multiple years in the wild.

Behavior

These chipmunks are generally solitary creatures that move around their small home ranges. During the winter, some hibernate, become less active or simply seek shelter during periods of severe weather. (; Hammerson, 2013; Sutton and Patterson, 2000)

  • Range territory size
    2000 to 40000 m^2

Home Range

Their home range and territory sizes are likely the same. Their home range is generally small, ranging from about 0.5 to 1.0 hectare (5000 to 10000 m^2). Other reports place this limit at 0.2 to 4.0 ha. Most individuals stay in one general area but are capable of moving up to 5 km to reach a suitable habitat. (; Hammerson, 2013)

Communication and Perception

Siskiyou chipmunks are known for having a distinct call of one long, intense syllable. Their call starts low in frequency, rises and falls again. When measured, the calls begin at 300 kHz, rise to 1,600 kHz or greater, then fall back to about 400 kHz. ("Tamias siskiyou", 2013)

Food Habits

Siskiyou chipmunks are fungivores, feeding on mature fruiting bodies of mycorrhizal fungi that grow within plant roots in a symbiotic relationship. This species also feeds on various plants, seeds, nuts and insects. Siskiyou chipmunks store food in a cache in preparation for the winter months. (; McIntire, 1984)

  • Animal Foods
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit
  • Other Foods
  • fungus

Predation

Siskiyou chipmunks have coloration similar to their environment and stay beneath herbaceous cover to avoid predation. Their predators include various mammals, snakes, hawks and owls. Since they are mainly diurnal animals, their coloration blends in with the environment. However, this adaptation is not as helpful against nocturnal predators. (; Sutton and Patterson, 2000)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

These chipmunks spread seeds and fungal spores from their food in their feces, in this way they help maintain plant biodiversity. (McIntire, 1984)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

As a fungivore, Siskiyou chipmunks spread fungal spores, Rhizopogon spores are the most common. Certain types of fungus can improve tree growth through root uptake. Therefore, these chipmunks indirectly supplement forest health and biodiversity, which can impact potential logging. (Jacobs and Luoma, 2008)

Economic Importance for Humans: Negative

There are no known adverse effects of Siskiyou chipmunks on humans.

Conservation Status

Currently, there are no known threats to the population of Siskiyou chipmunks.

Other Comments

Siskiyou chipmunks were once thought of as an intermediary species between the neighboring yellow-cheeked chipmunks and Allen's chipmunks. Their previous names include Eutamias townsendii siskiyou, Eutamias siskiyou and Neotamias siskiyou. (Sutton and Patterson, 2000)

Contributors

Natalie Singleton (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mycophage

an animal that mainly eats fungus

native range

the area in which the animal is naturally found, the region in which it is endemic.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

1990. California Department of Fish and Game Book: Siskiyou chipmunk. Sacramento: California Department of Fish and Game.

2013. "Tamias siskiyou" (On-line). Smithsonian National Museum of Natural History: North American Mammals. Accessed April 05, 2013 at http://www.mnh.si.edu/mna/image_info.cfm?species_id=387.

Hammerson, G. 2013. "Neotamias siskiyou" (On-line). NatureServe Explorer. Accessed April 04, 2013 at http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Neotamias%20siskiyou.

Jacobs, K., D. Luoma. 2008. Small mammal mycophagy response to variations in green-tree retention. Journal of Wildlife Management, 72/8: 1747-1755.

Johnston, A., R. Anthony. 2008. Small-mammal microhabitat associations and response to grazing in Oregon. Journal of Wildlife Management, 72/8: 1736-1746.

McIntire, P. 1984. Fungus consumption by the Siskiyou chipmunk within a variously treated forest. Ecology, 65/1: 137-146.

Sutton, D., B. Patterson. 2000. Geographic variation of the western chipmunks Tamias senex and T. siskiyou, with two new subspecies from California. Journal of Mammalogy, 81/2: 299-316.