Tamias merriami

Geographic Range

Merriam's chipmunks ( Tamias merriami ) are distributed throughout central and southern California. In particular, they occurs below 2700 m in the South Coast, Transverse, Peninsular, and Southern Sierra Nevada ranges.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Merriam's chipmunks occur in habitats that have trees, shrubs, logs, stumps, snags, rocks, and litter. An important factor is understory brush that they use for foraging. These animals inhabit chaparral, oak and pine forests, thickets by streams, and are often found around rock outcroppings. They also inhibit a wide variety of habitats if there are no competing species, such as black bears, mule deer, wild pigs, deer mice, kangaroo rats, and woodrats.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• chaparral chaparral
• forest forest

Physical Description

Merriam's chipmunks are grayish-brown, with dark stripes of equal width on the dorsal area. The stripes are typically gray or brown, rarely black. The belly and cheeks are white. The tail is long and bushy, and is usually edged with dull white. The average length of the head and body is 134.6 mm. Length of tail is 109.5 mm. The average mass is 71.8 g from males and 77.8 g for females. Hind foot length averages 35.8 mm. The length of the rostrum is 14.1 mm. Braincase length is 24.2 mm. The length of the maxillary tooth-row is 5.9 mm. The length of nasals is 12.1 mm for males and 12.6 mm for females. Width of nasals is 2.5 mm. The depth of the cranium is 14.7 mm. The dental formula for Merriam's chipmunks is i 1/1, c 0/0, p 2/1, m 3/3 = 22.

Merriam's chipmunk seems to follow Gloger's rule. The darker populations occur in the humid coastal areas of the redwood forests from San Francisco Bay southward. The palest populations are in single-leaf pinyon forests in Walker Pass in the semi-arid Kern Basin and on the eastern slope of the Sierra Nevada.

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

• Sexual Dimorphism
• female larger

Reproduction

The nature of the mating system in T. merriami has not been reported. However, the act of mating has been well described. Females attract males by calling to them. Females call for 10 to 20 minutes intervals. These intervals of calling may take up 3 to 4 hours of a female's day. A male will approach a calling female and perform a display. During this display, the male runs and leaps around the female. Then he will nuzzle his face on the female's face. The female may go into a crouching postion, allowing the male to mount her. In one instance, copulation consisted of four series of pelvic thrusts. There were 12 to 24 thrusts in each series, and each series of thrusts lasted about four seconds. After each series, the male rested and brushed his face side to side on the back of the female's neck. The entire copulation lasted for about 18 seconds.

Merriam's chipmunks breed from mid-January to June, with a peak during April. Gestation is about thirty-two days. Average litter size is four, but ranges from three to eight. Females have one litter per year. Mothers spend most of their time with their young for about two weeks. Nests are made in logs, stumps, snags, and burrows. Males that survive the breeding season are usually in poor condition. They will go to their burrows to recover in May and stay there until August or September.

The young are altricial, and must develop some before they emerge from the natal burrow or nest. At about one month of age, the young are able to leave the burrow. Their movements are uncoordinated, and they do things like go down trees backwards, rather than head-first. It takes about two weeks for them to develop the ability to jump accurately.

There is an extended period of juvenile learning after emergence from the natal burrow or nest. The young go through a predictable pattern of behavioral development, including exploration of the area around their shelter, tandem following, recognition of trails, recognition of food, increased alertness to the mother's expressions, play, increased area of exploration, and development of dominance rankings.

Sexual development is apparently variable. By 11 weeks of independence, the young of the year are about the same size as adults, but maintain a distinct subadult pelage. Puberty is marked in females by a pinkening of the genitals, swelling of the vulva and rupture of the covering membrane.

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

The young of this species are altricial, and do not leave the nest until they are about a month of age. When the young chipmunks become active in the nest, their senses are functional. The first day out of the nest, the young will give alarm and agitation calls. It takes about two weeks for the young to develop accuracy in jumping. Young learn how to forage by following their mother around.

• Parental Investment
• altricial altricial
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • protecting
    • female
• extended period of juvenile learning

Lifespan/Longevity

Merriam's chipmunks can live up to 5 years in the wild.

Behavior

Merriams's chipmunks are diurnal and most do not hibernate. At high elevations, some may hibernate to avoid the snow and cold. During the fall, they collect and cache food, choose a shelter spot, and feed to increase thier mass. During the winter, males form groups and display for precourtsip. Mating continues through spring. In the summer, adults molt and gain weight.

Merriam's chipmunks use woodpecker cavities, natural cavities, and burrows from pocket gophers for night shelter. Most night shelters face east. They usually do not forage more than 300 meters from their night shelter. Merriam's chipmunks travel along tree branches and logs. The trails are communal and are used generation after generation.

• Key Behaviors
• terricolous
• diurnal diurnal
• motile motile
• sedentary sedentary
• dominance hierarchies dominance hierarchies

Home Range

Most members of this species forage within an range of 300 meters of their night shelter.

Communication and Perception

Merriam's chipmunks use four main calls. The "chuck" has a narrow frequency range and causes others to be quiet and to hide. The "chip" has a wide frequency range and can be located without difficulty. It is usually made by a chipmunk by its den and incites others to call. The "trill" is usually intertwined with the chip and is used for alarm. Lastly, the "chipper" is a series of disorderly notes made from an individual who has been scared and is going for cover.

Scent communication is also important. These animals have functional scent glands by the age of 4 weeks. The vulva emits an odor important for reproduction. Scent marking is common.

In addition, there is tactile communication during mating and between a mother and her offspring. Because the species is diurnal and social, it is likely that visual signals, such as body postures, are also used.

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

• Other Communication Modes
• pheromones pheromones
• scent marks scent marks

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

Food Habits

Evidence has shown that Merriam's chipmunks consume more than seventy species of plants. Acorns are a major food source throughout the year. These animals will also consume insects, lizards, muscle tissue of sparrows, seeds found in the feces of goldfinches, and embyronic membrane from eff shells of California quail.

They have two daily forages and a resting period during midday. The first foraging period is in the morning and lasts about three and half hours of constant activity. The second foraging is more relaxed and ends when they goes into their shelter for the night. Searching for food to store in caches takes up most of its active time. Foraging areas are jointly used and there is seldom conflict over food. These animals search for food in forest understory and in trees.

Using their cheekpouches they carry food to another site where they remove the husk and then eat the seeds. If they cache an acorn, they do not remove the husk. They make a pit about 3.8 cm deep and deposit a single acorn. They cover the hole with leaf litter and soil. Merriam's chipmunks also store food in dead logs, between limbs, and branches of trees. When storing food, females generally cache acorns further apart than males.

• Primary Diet
• herbivore herbivore
  • granivore granivore

• Animal Foods
• birds
• reptiles
• eggs
• insects

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

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

Predation

Merriam's chipmunks are prey to several species. These include long-tailed weasels ( Mustela frenata ), bobcats ( Lynx rufus ), coyotes ( Canis latrans ), gray foxes ( Urocyon cinereoargenteus ), sharp-shinned hawks ( Accipiter striatus ), badgers ( Taxeda taxus ), Coopers's hawk ( Accipiter cooperii ), great horned owls ( Bubo virginiana ), Pacific rattlesnakes ( Crotalus viridis ), garter snakes ( Thamnophis ), gopher snakes ( Pituophis melanoleucus ), and domestic cats ( Felis domesticus ).

Ecosystem Roles

Merriam's chipmunks are prey items for a wide variety of carnivores. They also cache acorns, which may help disperse oak trees.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

There is no specific information available on this topic. However, these animals are cute and can be entertaining to people who view them scurrying about. Also, they serve as food for predators which people also enjoy watching. Although this does not exactly make Merriam's chipmunks a source of ecotourism, it should be noted that even without substanitial economic impact on humans, there is some human benefit from this species.

Economic Importance for Humans: Negative

This species has no reported negative economic impact on humans.

Conservation Status

Merriam's chipmunks are not listed by CITES or IUCN.

Additional Links

Encyclopedia of Life

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Kim May (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

References

Best, T., N. Granai. 1994. Tamias merriami. Mammalian Species , 476: 1-9.

Callahan, J., S. Compton. 1995. Reproductive behavior in Merriam's chipmunk. Great Basin Naturalist , 55/1: 89-91.

Harvey, T., C. Polite. 1999. "California Wildlife Habitat Relationship System" (On-line). Accessed May 07, 2004 at http://www.dfg.ca.gov/whdab/html/M060.html .