Tamias amoenus

Geographic Range

Yellow-pine chipmunks, Tamias amoenus , are found in the northwestern United States and southwestern Canada. They occur throughout Idaho, Washington, and Oregon (excluding coastal areas), as well as northern Nevada and northern Utah, western Wyoming and western Montana, and mountainous areas of California. In Canada, yellow-pine chipmunks occupy most of southern British Colombia and the mountainous regions of southwestern Alberta.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Yellow-pine chipmunks are most common in brushy coniferous forests, but can be found in a broad range of habitat types including areas with rocky outcrops, chaparral, and meadows. They occupy areas that are dominated by shrubs such as service berry ( Amelanchier ), snowberry ( Symphoricarpos ), mountain mahogany ( Cercocarpus ), currant ( Ribes ), antelope brush ( Purshia ), and buckbrush ( Ceanothus ).

Yellow-pine chipmunks require logs, snags, rock crevices, or stumps for nesting, in addition to shrubs and ground litter for cover.

Yellow-pine chipmunks typically occur at altitudes ranging from 600 to 2,800 m, however in Washington they have been recorded at elevations of up to 4,300 m.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• chaparral chaparral
• forest forest
• mountains mountains

• Other Habitat Features
• riparian riparian

Physical Description

Yellow-pine chipmunks are small compared to other members of the genus Tamias . They measure 181 to 245 mm in length, and can weigh between 30 and 70 g. Females tend to be larger than males.

These animals have five black, evenly-spaced, longitudinal stripes down the back. The three dorsal stripes extend from shoulder to rump, whereas the two lateral strips extend only to mid-body. The pale stripes are usually white or grayish. Body color varies depending upon subspecies. Tamias amoenus affinis has a pinkish-cinnamon colored body, T. a. monoensis is a cinnamon buff, T. a. luteiventris is sayal-brown, T. a. felix is ochraceous tawny, and T. a. ludibundus is tawny. The underside of the tail ranges from pinkish-cinnamon to grayish-yellow to sayal-brown. The ears are whitish behind and black in front.

Yellow-pine chipmunks can be distinguished from similar species by the genital bones of both sexes. They can also be distinguished based upon size and color. Lodgepole chipmunks are larger than yellow-pine chipmunks, have bigger ears, and more sharply contrasting stripes. The outer stripes of lodgepole chipmunks are also wider than the inner stripes. Least chipmunks are smaller than yellow-pine chipmunks, and also paler in color. Yellow-pine chipmunks are smaller and redder than Unita chipmunks . Unita chipmunks also have grayer shoulders and heads.

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

• Sexual Dimorphism
• female larger

Reproduction

Yellow-pine chipmunks are polygynandrous. Females are in estrous for one day each year. They use vocalizations to attract mates a few days before the onset of estrous. On the day of estrous, females are typically pursued by two to six males in what is called a “mating chase”. A female mates with multiple males during this mating chase. All sexually mature males and females mate during the mating season, which occurs in late April or early May.

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

Female yellow-pine chipmunks are in estrous for one day and breed only once per year during late April to early May. Average gestation period is 30 days, after which a female usually gives birth to a litter of 3 to 8 babies. Young are highly altricial at birth and remain in the burrow until they are weaned at six weeks of age. Young begin to disperse and find their own burrows at about 8 to 12 weeks of age. They reach sexual maturity at 12 to 23 months.

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

Pregnant females make nests of leaves, grass, lichen, and feathers in burrows that are about 1.5 m below ground or up to 18 m in trees. Babies are altricial and depend on the mother for food and protection until they emerge from the burrow at about 6 weeks of age. Males do not contribute to the care of the offspring. At about 8 weeks of age, young of both sexes disperse to find their own nests and burrows for winter.

• Parental Investment
• altricial altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Yellow-pine chipmunks have been known to live up to 5 years 2 months in the wild. Young have a 30% survival rate. Once they emerge from the den at about 6 weeks of age, they are easy prey for a variety of predators. Adults have a summer survival rate of 33% to 88% and a winter survival rate of 97%.

No information was available on the lifespan and survival rate of captive yellow-pine chipmunks.

Behavior

Yellow-pine chipmunks are solitary except during the breeding season in late April and early May. They are active from just before sunrise until about a half hour after sunset. The chipmunks return to their burrows during the middle of the day and are rarely seen from 0900h to 1500h. On cloudy days, or days with light rain, they may be active all day.

Most of a yellow-pine chipmunk's day is spent foraging or grooming. These animals frequently brush their fur, take dust baths, and wash their faces. Like most chipmunks , yellow-pine chipmunks move with short jerky movements. The tail is held horizontally or erect during running, and swings from side to side as an individual sits. Foraging typically takes place in areas with shade and shrub cover.

Yellow-pine chipmunks enter a state of torpor for about four months during the winter. When in torpor, they emerge every 5 to 7 days to eat seeds stored in various caches. Caches have been recorded to contain up to 68,000 items. Yellow-pine chipmunks do not gain a heavy fat layer in winter like most other chipmunks . They enter torpor when temperatures drop below 23˚C and photoperiods begin to decrease.

Yellow-pine chipmunks are often found in association with golden-mantled ground squirrels and well as least chipmunks . When engaging in interspecific competition with least chipmunks , yellow-pine chipmunks are dominant.

• Key Behaviors
• terricolous
• diurnal diurnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• hibernation hibernation
• solitary solitary

Home Range

Home ranges for males range from 0.4 to 2.8 ha and average 1.3 ha. Female home ranges are smaller, ranging from 0.1 to 1.1 ha and averaging about 0.6 ha.

Yellow-pine chipmunks are not territorial and may have overlapping home ranges, however they will defend areas that are in the immediate vicinity of the entrance to their burrows.

Communication and Perception

Yellow-pine chipmunks have 10 different recognizable vocalizations. Most of these calls are alarm calls to alert conspecifics of predators. When greeting conspecifics, they first touch noses, then smell the sides of the face and neck, and last they sniff the anus. Visual signals, such as body posture, are important in communication.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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

Food Habits

Yellow-pine chipmunks are mostly omnivorous. They consume at least 59 species of seeds, plants, fruits, fungi, corms, and insects. They are also known to eat small mammals, bird eggs, and roots. They use their cheek pouches to carry conifer seeds and other foods to their burrows.

These chipmunks forage both on the ground and in trees. Foraging is done during the day and from spring to fall. In the fall, they begin storing food in caches for winter. Winter caches of up to 68,000 items, ranging from seeds to bumble bees, have been recorded.

• Primary Diet
• omnivore omnivore

• Animal Foods
• mammals
• eggs
• insects
• terrestrial non-insect arthropods
• terrestrial worms

• Plant Foods
• leaves
• roots and tubers
• seeds, grains, and nuts
• fruit
• flowers

• Other Foods
• fungus

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

Predation

Yellow-pine chipmunks usually live in underground burrows, which help conceal them from predators. The black and white stripes on the back of these animals help to camouflage them in open forests where sharp shadows are cast by the sun. They also have, to some extent, a system of watch where one chipmunk looks out for predators and warns the others with alarm vocalizations. This is mostly observed in more open areas where chipmunks are more exposed to predators.

Predators include coyotes ( Canis latrans ), goshawks ( Accipiter gentilis ), long-tailed weasels ( Mustela frenata ), badgers ( Taxidea taxus ), bobcats ( Lynx rufus ), rattlesnakes ( Crotalus viridis ), and sparrow hawks ( Falco sparverius ).

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Yellow-pine chipmunks are important dispersers of the seeds of various conifer species. They also contribute to the food base of many different carnivore species.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Like most chipmunks, yellow-pine chipmunks are favored among nature lovers. This species is less destructive of young conifers (often harvested by humans for timber) than other small mammals.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

Yellow-pine chipmunks have been identified as hosts for the disease vectors responsible for Colorado tick fever, tick-borne relapsing fever, hantavirus pulmonary syndrome, and Rocky Mountain spotted fever richettsia. They also become heavily infested with bot fly warbles and fleas that are known to carry plague.

Destruction by yellow-pine chipmunks of young conifers intended for timber harvest has been documented, however the overall damange is insubstantial.

• Negative Impacts
• injures humans
  • causes disease in humans causes disease in humans
  • carries human disease
• causes or carries domestic animal disease causes or carries domestic animal disease

Conservation Status

Yellow-pine chipmunks are common in the northwestern United States and southwestern Canada. The species has no special status.

Additional Links

Encyclopedia of Life

Contributors

Melissa Looney (author), Humboldt State University, Brian Arbogast (editor, instructor), Humboldt State University.

Nancy Shefferly (editor), Animal Diversity Web.

References

Banfield, A. 1974. The Mammals of Canada . Toronto: University of Toronto Press.

Harvey, T., C. Polite. 2003. "California Department of Fish and Game" (On-line). California Wildlife Habitat Relationships System. Accessed March 01, 2005 at http://www.dfg.ca.gov/whdab/html/M055.html .

Kays, R., D. Wilson. 2002. Mammals of North America . Oxfordshire: Princeton University Press.

Larrison, E. 1976. Mammals of the Northwest: Washington, Oregon, Idaho, and British Columbia . Seattle: Seattle Audubon Society.

Schulte-Hostedde, A., J. Millar, L. Gibbs. 2002. Female-biased sexual size dimorphism in the yellow-pine chipmunk (Tamias amoenus): sex-specific patterns of annual reproductive success and survival. Evolution , 56/12: 2519-2529.

Sutton, D. 1992. Tamias amoenus. Mammalian Species , 390: 1-8.

Verts, B., L. Carraway. 1998. Land Mammals of Oregon . Los Angeles: University of California Press.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals . Washington: Smithsonian Institute Press.

Zeveloff, S., F. Collett. 1988. Mammals of the Intermountain West . Salt Lake City: University of Utah Press.

eNature.com, Inc. 2003. "National Wildlife Federation" (On-line). eNature.com. Accessed February 18, 2005 at http://www.enature.com/fieldguide/showSpeciesSH.asp?curGroupID=5&shapeID=1041&display=2&curPageNum=32&recnum=MA0129 .