Sciuridae fossils have been found worldwide, however their biogeography (dispersal over evolutionary time) is still obscure. No fossil from the Pleistocene era has been found of Townsend's chipmunks.
Townsend's chipmunks perceive their environment through sight, hearing, and smell, but communicate using vocalizations, threat displays, and touch. Their most important method of communication is vocalizations, primarily alarm calls made by males, females, adults, and juveniles. This is an interesting behavior, because even if the Tonwsend's chipmunks tend to be solitary, they give alarm calls to warn their conspecifics, compromising their own survival. This can be considered as altruism. This phenomenon seems to be more important when the chipmunks are genetically related. This involve kin selection: they are able to recognize individuals to which they are more related. This is mainly accomplished by familiarization when they are young, such as sniffing and grooming.
Communication Channels: tactile ; acoustic
Other Communication Modes: pheromones
Perception Channels: visual ; tactile ; acoustic ; chemical
Townsend's chipmunk populations are quite stable. They are not threatened and are considered quite common. Herbicide treatment of Douglas-fir plantations caused a decline in a coastal population in British Columbia in the 1980's, but only temporarily. Their density ranges from 0.6 to 1.1 individuals per hectare in a mature forest, but may be 2 to 4 times higher in clear-cuts (3 to 10 years after the cut).
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Townsend's chipmunks are potential fungus dispersers, which mean they can also be an agent in the dissemination of harmful fungus, especially for conifer seeds. Thus they can cause problems in commercial forestry, though on a limited scale.
Townsend's chipmunks rely partially on a mycophagous diet, so they can potentially play a role in forest ecology. They can disperse fungi that contribute to create enriched soils, resulting in a global enhancement of soil quality in the forest. Thus it might be an advantage in commercial forestry.
Townsend's chipmunks are mainly primary consumers (though they do not feed exclusively on plants), enabling energy flows from primary producers to secondary consumers. Townsend's chipmunks are potential seed dispersers. They partially feed on seeds which may end up in their feces because of their low digestibility. Moreover, they store seeds in their burrows, and even if they consume these during winter, some might remain at the beginning of the spring and germinate. They may also participate in fungi dispersal. They spread the spores by carrying them on their feet, and by eating fungi, can also disperse them in their feces. Townsend's chipmunks can be host for some parasites like coccidain parasites (Eimeria) and contribute to their propagation in the ecosystem.
Ecosystem Impact: disperses seeds
Commensal/Parasitic Species:
Townsend's chipmunks have a fairly diverse diet. Underground fungi (truffes) emit a strong odor and seem to be the favorite food of the Townsend's chipmunks, especially during winter. Thus they are primarily mycophagous, but tend to diversify they diet depending upon the availability of the different resources. During the summer, they feed mainly on berries including blackberries (Rubus fruticosus), salal berries (Gaultheria shallon), and thimble-berries (Rubus parviflorus). In the fall, their diet tends to switch to seeds: maple (Acer pseudoplatanus) seeds, thistle (Cynareae) seeds, grain seeds, conifer seeds, but also acorns (Quercus), huckleberries (Vaccinium and Gaylussacia), grass and roots. Townsend's chipmunks forage mainly on the ground, but may also climb in trees. They use their cheek pouches to carry food from their foraging areas to their burrow.
Animal Foods: insects
Plant Foods: roots and tubers; seeds, grains, and nuts; fruit
Other Foods: fungus
Foraging Behavior: stores or caches food
Primary Diet: omnivore ; mycophage
Townsend's chipmunks are found in the northwestern United States. Their distribution ranges from the the Rogue River in southern Oregon to southwestern British Columbia along the Pacific coast. Thus they are found in an oceanic, or marine west coast climate.
Biogeographic Regions: nearctic (Native )
Townsend's chipmunks are mainly found in dense hardwood forests and dense coniferous forests. They tend to live in riparian areas within the forests, or in areas with dense shrub cover which influence their behavior. They can sometimes reach more open areas, like clear-cut forests, especially several years after the cut when the secondary forest is growing. This provides shrub cover and an abundant source of food. Their home range extends from the coast to the sub-alpine areas of the Cascade Range in Oregon. For nesting, they look for talus slope with lose rocks that provide a shelter.
Range elevation: 0 (low) m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest
Other Habitat Features: riparian
In captivity, an individual Townsend's chimpunk lived to 9.3 years. Another specimen has been said to have lived up to 10.2 years, but this was inadequately documented. In the wild, Townsend's chipmunks live 2 to 7 years, with an expected lifespan of 5 years. Food availability may be a limiting factor in populations, and might reduce survival and reproduction.
Range lifespan
Status: wild: 2 to 7 years.
Range lifespan
Status: captivity: 10.2 (high) years.
Typical lifespan
Status: wild: 7 (high) years.
Average lifespan
Status: wild: 5 years.
Average lifespan
Status: captivity: 7 hours.
Townsend's chipmunks have dark brown and striped backs. There are five dark stripes alternating with four lighter stripes; the middle one is usually darker. Unlike squirrels, chipmunks have striped faces. Townsend's chipmunks have two gray and three brown stripes on their faces. Other anterior stripes might also be observed, but they are mostly obsolete. Underparts are creamy white to gray. Ears are black in front and gray behind. The bushy tail is dark brown to dark tipped with gray above, and brown below. The tail is held erect while running. Townsend's chipmunks tend to be brighter during the summer, and undergo two molts annually in May and August. Juvenile pelage is similar to adults.
Townsend's chipmunks are considered fairly large among chipmunks. Their size range from 22 to 38 cm, and averages 25.5 cm. This includes a tail of 7 to 17 cm. Their weight ranges from 60 to 118 g, and averages 75 g. Females are 2% to 6% larger than males, which leads to a female dominance in the population.
Their dental formula is: 1/1 0/0 2/1 3/3 =22, with a small vestigial upper premolar that all western North American chipmunks possess and eastern North American do not.
Range mass: 60 to 118 g.
Average mass: 75 g.
Range length: 22 to 38 cm.
Average length: 25.5 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger
Townsend's chipmunks use alarm calls to warn other individuals, especially their relatives. Their small size and color of fur also make them cryptic, which is an advantage for a prey. They also display some behavioral adaptations like the preference for covered areas. Townsend's chipmunks are preyed upon by weasels (Mustela), minks (Neovison vison), bobcats (Lynx rufus), house cats (Felix catus), foxes (Vulpes), martens (Martes), skunks (Mephitidae), hawks (Accipitrinae), owls (Strigiformes), and snakes (Serpentes).
Known Predators:
Anti-predator Adaptations: aposematic ; cryptic
There is little documentation regarding mating systems of Townsend's chipmunks. Mating is seasonal and occurs for 2 weeks in spring. Like most chipmunks, they are likely not promiscuous, nor do they form a pair bond.
Mating System: polygynandrous (promiscuous)
Townsend's chipmunks only breed once a year for a period of 2 weeks right after hibernation. This is so that all reproduction activities can occur between late spring and early summer, when food availability and climate are more favorable. In this way, young can mature during summer and prepare for winter.
Townsend's chipmunks are viviparous. Gestation lasts 28 days and parturation occurs from May to June. Females give birth to 3 to 6 young in their burrows. At birth the young have no hair or teeth. Their eyes are closed, ears folded, feet webbed, and skin translucent. They weigh around 3.5 g. At 10 days, dorsal hairs have begun to grow on their back, and their eyes are still closed. They are not totally helpless, but are able to use their forelimbs to move by pulling and pushing. By 20 days, they have fur, incisors, and are more active. They appear above ground in July, when food and climate conditions are favorable. At the end of the 50-day weaning period, they weigh around 35 g. At 90 days, they are considered adults. Adults reach sexual maturity at 353 days, and Townsend's chipmunks can reproduce the following summer.
Breeding interval: Townsend's chipmunks breed once a year.
Breeding season: Townsend's chipmunks breed for 2 weeks in spring, usually in late April.
Range number of offspring: 3 to 6.
Average gestation period: 28 days.
Average weaning age: 50 days.
Average time to independence: 90 days.
Average age at sexual or reproductive maturity (female): 353 days.
Average age at sexual or reproductive maturity (male): 353 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Pups are altricial at birth, so the mother provides protection and sustenance. She primarily keeps them in the burrow, and feeds them milk until they transition to an omnivorous diet. The mother nurses the young until they leave the burrow and become independent.
Parental Investment: altricial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
