Tamias siskiyou

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 .

• Biogeographic Regions
• nearctic nearctic
  • native native

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.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

• Other Habitat Features
• riparian riparian

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.

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 .

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

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.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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.

• Parental Investment
• female parental care female parental care

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.

• Key Behaviors
• arboreal arboreal
• diurnal diurnal
• motile motile
• sedentary sedentary
• hibernation hibernation
• solitary solitary

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.

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.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• mycophage mycophage

• Animal Foods
• insects

• Plant Foods
• seeds, grains, and nuts
• fruit

• Other Foods
• fungus

• Foraging Behavior
• stores or caches food stores or caches food

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.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

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

• 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.

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 .

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

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.

References

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.

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 .

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