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Tuesday, July 19, 2011

Merriam's Chipmunk

Beauty Of Animal | Merriam's Chipmunk  | 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. (Harvey and Polite, 1999) 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. (Best and Granai, 1994)
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. (Best and Granai, 1994)
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. (Best and Granai, 1994) 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. (Callahan and Compton, 1995)

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. (Best and Granai, 1994; Harvey and Polite, 1999)

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