Yellow-cheeked chipmunks are the largest members of their group (subgenus Neotamias), which includes most Townsend’s chipmunks of western North America. They range in length from 233 to 297 mm. Their tails range from 97 to 130 mm in length. The markings on their fur have alternating bands of black (5 bands) and light tan (4 bands) running lengthwise along their back. They also have two other sets of bands of similar coloration above and below their eyes. As with other chipmunks of their group, they have a pale tan or yellowish underbelly. Their fur is different at different times of the time of year. They shed twice each year, once in the fall and again in the spring. Their winter coat is notably longer, softer, and denser. Although yellow-cheeked chipmunks are similar to other members of their group, they are distinguished by their genetics, vocalizations, and anatomy. They make sounds known as 'chip vocalizations', which consist of paired syllables, resulting in a “chip-chip” call. On average, female yellow-cheeked chipmunks are about five percent larger than males; this is known as sexual dimorphism. (Foley and Neito, 2011; Gannon and Lawlor, 1989; Gannon, et al., 1993; Roberson, 2009)
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)
Yellow-cheeked chipmunks make burrows for stashing food and avoiding predators. These burrows are huge and made in dense forest 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. (Foley and Neito, 2011; Rosenberg and Anthony, 1993)
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 were available for breeding for only one day at a time, when this occurs, they usually mate with multiple males. (Gashwiler, 1976; Roberson, 2009)
Males are in breeding condition during March, April, and May. Females are in breeding condition about a month after males, and maintain it for about two months longer. Litters range from two to five young, with an average litter size of four. (Gannon, et al., 1993; Gashwiler, 1976; Polite and Harvey, 2000)
There was no data found for this specific species; however, the young of most chipmunks are altricial, meaning they are far from independent and require a lot of parental care. (Roberson, 2009)
No reliable data exists specifically for this species. However, in one study, the oldest yellow-cheeked chipmunk was two years old. This is probably much lower than their actual lifespan. Eastern chipmunks, a close relative of yellow-cheeked chipmunks, live 3 to 4 years. (Foley and Neito, 2011; Levenson, et al., 1985)
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 large networks of many small tunnels. Nest cups have not been found in burrows, this suggests yellow-cheeked chipmunks only use their burrows occasionally. Chipmunks are considered solitary animals; they are rarely social outside of the breeding season. (Foley and Neito, 2011; Roberson, 2009)
Female yellow-cheeked chipmunks inhabit areas ranging from 0.005 to 0.24 kilometers squared and males inhabit areas ranging 0.006 to 0.73 kilometers squared. Males travel maximum distances of 0.1 to 1.26 kilometers, while females traveled 0.14 to 0.63 kilometers. Although chipmunks are not social, they are also not usually territorial, their home ranges often overlap. (Foley and Neito, 2011; Roberson, 2009)
Yellow-cheeked chipmunks make low frequency calls, as compared to other chipmunks. These calls include two quick chirps that are repeated. These calls are unique enough to distinguish them from other species. Chipmunks also use visual cues to communicate with each other. (Gannon and Lawlor, 1989; Roberson, 2009)
At the end of winter and beginning of spring, a large part of their diet is fungus. The rest of the year they eat a variety of foods. Based on the contents of their cheek pouches, yellow-cheeked chipmunks likely eat the following: western raspberry, buckthorn, blue-blossom, wax myrtle, California huckleberry, poison oak, bull thistle, scotch broom, and acorns. Yellow-cheeked chipmunks may also eat insects. (Gannon, et al., 1993)
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)
Since yellow-cheeked chipmunks live both on the ground and in trees, they may transfer diseases and parasites to 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 a tendency to stash food in burrows makes them important seed dispersers, although some chipmunks destroy certain types of seeds. Chipmunks are also important in the spread of mycorrhizal fungi. (Foley and Neito, 2011; Gannon, et al., 1993; Roberson, 2009)
Chipmunks can become pests, they form dense populations and their nesting and feeding habits are very general. When living close to humans they can cause damage 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 sickness in humans, domestic animals and wildlife. Chipmunks also carry various other tick transmitted diseases, including the Hantavirus. (Foley and Neito, 2011; Linzey and Hammerson, 2008; Roberson, 2009)
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)
Mark Fletcher (author), University of Alaska Fairbanks, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
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