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Tamias ochrogenysyellow-cheeked chipmunk

By Mark Fletcher

Geographic Range

Yellow-cheeked, or redwood chipmunks (Tamias ochrogenys), have a narrow distribution in California. Their home range is a small patch along the coast of the northern part of the state that extends no more than 40 kilometers from the shore. The range of this species begins in Sonoma County and extends north to the Eel River, in Humbolt County. Their entire range is less than 20,000 kilometers squared. (Gannon and Lawlor, 1989; Gannon, et al., 1993; Linzey and Hammerson, 2008)

Habitat

Yellow-cheeked chipmunks make burrows for stashing food and avoiding predators. These burrows are extensive and made in dense undergrowth and downed trees. These animals rely on coastal redwood forests and mixed coniferous or Douglas fir forests for their habitat; although they are rarely found in the tree canopy. A study showed significantly greater densities of chipmunks of this group in old growth, versus secondary forests. (Foley and Neito, 2011; Rosenberg and Anthony, 1993)

  • Range elevation
    Sea level to 1280 m
    to 4199.48 ft

Physical Description

Yellow-cheeked chipmunks are the largest members of the subgenus Neotamias, which includes most Townsend’s chipmunks of western North America. They range in length from 233 to 297 mm. Their tail ranges from 97 to 130 mm in length. Their pelage markings consist of alternating bands of black (5 bands) and light tan (4 bands) running dorsally along their back. Two other sets of bands of similar coloration are present above and below their eyes. As with other chipmunks of the group Neotamias, pale tan or yellowish pelage covers their underbelly. The time of year and stage of molt play an important role in their pelage appearance. They shed twice each year, in the fall, then again in the spring. Their winter coat is notably longer, softer, and denser. There are three prominent characteristics that distinguish T. ochrogenys from other members of the Neotamias group including genetics, chip vocalization, and anatomical variation (of genitalia). The chip vocalization consists of paired syllables, resulting in a “chip-chip” call. The baculum of T. ochrogenys is longer and thicker than that of other Neotamias chipmunks. Yellow-cheeked chipmunks show slight sexual dimorphism, females are about five percent larger than males on average. Their dental formula is 1/1 0/0 2/1 3/3 total=22. (Foley and Neito, 2011; Gannon and Lawlor, 1989; Gannon, et al., 1993; Roberson, 2009)

  • Sexual Dimorphism
  • female larger
  • Range mass
    78 to 117.5 g
    2.75 to 4.14 oz
  • Average mass
    94.1 g
    3.32 oz
  • Range length
    233 to 297 mm
    9.17 to 11.69 in

Reproduction

In a year, females will have no more than one litter. No data were found specific to this species, but in other species of chipmunks, females are in estrus for only one day and usually mate with multiple males. (Gashwiler, 1976; Roberson, 2009)

Males are in breeding condition during March, April, and May. Male testes increase in size during reproductive periods. Their testes are the largest in late March through June and gradually shrink through the fall months. Females begin to enter breeding condition about a month later than males, and maintain it for about two months longer. Litters range from two to five individuals, with an average litter size of four. (Gannon, et al., 1993; Gashwiler, 1976; Polite and Harvey, 2000)

  • Breeding interval
    Yellow-cheeked chipmunks breed once yearly.
  • Breeding season
    Yellow-cheeked chipmunks breed during mid-March and into the summer months.
  • Range number of offspring
    2 to 5
  • Average number of offspring
    4

There was no data found for this specific species; however, the young of most chipmunks are altricial. (Roberson, 2009)

Lifespan/Longevity

No reliable data exists specifically for this species. However, in one study, the longest lived specimen of T. ochrogenys was two years old. This was hypothesized to be a gross underestimate of their lifespan. Eastern chipmunks, a close relative of yellow-cheeked chipmunks, live 3 to 4 years. (Foley and Neito, 2011; Levenson, et al., 1985)

Behavior

This species is diurnal and does not hibernate; however, they are slightly less active in winter months. Their burrows are usually made in downed trees, and thick underbrush; often just above ground or slightly below. The burrows mainly consist of extensive networks of many small tunnels. Nest cups have not been found in burrows, suggesting that T. ochrogenys uses them sporadically. Chipmunks are considered solitary animals, rarely having extensive social interactions outside of the breeding season. (Foley and Neito, 2011; Roberson, 2009)

  • Range territory size
    0.005 to 0.73 km^2

Home Range

Using radio telemetry, it was determined that female yellow-cheeked chipmunks inhabit areas ranging from 0.005 to 0.24 km2 and males inhabit areas ranging 0.006 to 0.73 km2. In the same study, males traveled maximum distances of 0.1 to 1.26 km, while females traveled 0.14 to 0.63 km. Although chipmunks avoid social interaction, they are rarely considered territorial, their home ranges often overlap. (Foley and Neito, 2011; Roberson, 2009)

Communication and Perception

Yellow-cheeked chipmunks produce low frequency calls, as compared to their close relatives. They consist of two quick chirps that are repeated. These calls are considered diagnostic of the species and have been used to confirm the elevation of T. ochrogenys from a subspecies. Chipmunks also use visual cues to communicate with each other. (Gannon and Lawlor, 1989; Roberson, 2009)

Food Habits

At the end of winter and beginning of spring, a significant portion of their diet consists of fungi. The rest of the year their diet is very broad. The following dietary items of yellow-cheeked chipmunks are based on the contents of cheek pouches: western raspberry, buckthorn, blue-blossom, wax myrtle, California huckleberry, poison oak, bull thistle, scotch broom, and acorns. Yellow-cheeked chipmunks may also consume insects. (Gannon, et al., 1993)

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

Predation

Predators of yellow-cheeked chipmunks possibly include skunks, minks, weasels, martens, domestic cats, and numerous owl and hawk species. They use burrows and lower branches of trees to escape predation. Chipmunks use alarm calls to deter and confuse predators. These calls also warn other chipmunks in the area of possible danger. (Foley and Neito, 2011; Polite and Harvey, 2000; Roberson, 2009)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Since yellow-cheeked chipmunks are both ground dwelling and semi-arboreal, they are a possible vector of disease and parasite transfer to both woodrats and tree squirrels as they share habitats with both species. They are known hosts of western black-legged ticks (Ixodid pacificus). As with the diet of all chipmunks, their foraging behavior and tendency to stash food in burrows makes them important seed dispersers, although some chipmunks may destroy certain types of seeds. Chipmunks are important in the spread of mycorrhizal fungi. (Foley and Neito, 2011; Gannon, et al., 1993; Roberson, 2009)

  • Ecosystem Impact
  • disperses seeds
Commensal/Parasitic Species
  • western black-legged ticks (Ixodid pacificus) (class Arachnida; phylum Anthropoda)

Economic Importance for Humans: Positive

Chipmunks have immeasurable value to humans as dispersers of seeds and mycorrhizal fungi. (Gannon, et al., 1993; Roberson, 2009)

Economic Importance for Humans: Negative

Chipmunks can become pests, they form dense populations and their nesting and feeding habits are very general. When living in close proximity to humans they can cause destruction to gardens, homes, and campsites. Tamias ochrogenys are known hosts of western black-legged ticks (Ixodid pacificus). These ticks are known to transmit Anaplasma phagocytophilum, a bacterium that causes granulocytic anaplasmosis in humans, domestic animals and wildlife. Chipmunks have been identified as vectors for various other tick transmitted diseases, and even the Hantavirus. (Foley and Neito, 2011; Linzey and Hammerson, 2008; Roberson, 2009)

  • Negative Impacts
  • injures humans
    • carries human disease

Conservation Status

Yellow-cheeked chipmunks are common within their range and currently, no major threats have been identified. Population estimates for the species exceed 10,000 individuals and the population is reported to be stable. (Linzey and Hammerson, 2008)

Contributors

Mark Fletcher (author), University of Alaska Fairbanks, 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

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

carnivore

an animal that mainly eats meat

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.

folivore

an animal that mainly eats leaves.

forest

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

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

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.

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

Foley, J., N. Neito. 2011. The ecology of tick-transmitted infections in the redwood chipmunk (Tamias ochrogenys). Ticks and Tick-borne Diseases, 2/2: 88-93.

Gannon, W., D. Kain, R. Forbes. 1993. Tamias ochrogenys. American Society of Mammalogists, 445: 1-4. Accessed October 02, 2012 at //www.jstor.org/stable/3504118.

Gannon, W., T. Lawlor. 1989. Variation of the Chip Vocalization of Three Species of Townsend Chipmunks. Journal of Mammalogy, 70: 740-753.

Gashwiler, J. 1976. Biology of Townsend's chipmunks in Western Oregon. The Murrelet, 57, No. 2: 26-31.

Levenson, H., R. Hoffmann, C. Nadler, L. Deutsch, S. Freeman. 1985. Systematics of the Holarctic Chipmunks (Tamias). Journal of Mammalogy, 66/2: 219-242.

Linzey, A., G. Hammerson. 2008. "Tamias ochrogenys" (On-line). IUCN ed List of Threatened Species. Accessed October 02, 2012 at http://www.iucnredlist.org/details/42573/0.

Polite, C., T. Harvey. 2000. "Yellow-Cheeked Chipmunk Neotamias ochrogenys" (On-line). California Department of Fish and Game. Accessed November 15, 2012 at https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentVersionID=18162.

Roberson, D. 2009. "Chipmunks" (On-line). Accessed November 15, 2012 at http://creagrus.home.montereybay.com/chipmunks2.html.

Rosenberg, D., R. Anthony. 1993. Differences in Townsent's Chipmunk Populations between Second- and Old-Growth Forests in Western Oregon. The Journal of Wildlife Management, 57 No.2: 365-373. Accessed November 10, 2012 at http://www.jstor.org/stable/3809435.

Sutton, D. 1987. Analysis of Pacific Coast Townsend Chipmunks (Rodentia: Sciuridae). The Southwestern Naturalist, 32/3: 371-376.

Sutton, D. 1995. Problems of Taxonomy and Distribution in Four Species of Chipmunks. Journal of Mammalogy, 76/3: 843-850.

Waldien, D., J. Hayes, M. Huso. 2006. Use of Downed Wood by Townsend's Chipmunks (Tamias townsendii) in Western Oregon. Journal of Mammalogy, 87/3: 454-460. Accessed October 05, 2012 at http://www.jstor.org/stable/4094501.

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