Thirteen-lined Ground Squirrel

Spermophilus tridecemlineatus (Mitchill)

Description:   The thirteen-lined ground squirrel can be distinguished from other Kansas rodents by: 1) small ears, 2) elongated body, 3) thirteen yellowish-buff stripes (broken and solid) alternating with twelve dark brown stripes running from rump to shoulders, 4) underparts cinnamon buff, and 5) relatively short tail yellowish-brown and bordered with buff-tipped hairs. Long claws on the fore feet are employed digging, and internal cheek pouches are used to carry food. Males are slightly larger than females, but there is no difference in their color. Young are similar to adults in color.

Size:   Adults may attain the following dimensions: total length 222-295 mm; tail 67-118 mm; hind foot 31-37 mm; ear 8-12 mm; weight 83-185 grams.

Range and Habitat:   The thirteen-lined ground squirrel occurs throughout the state in dry areas of open, short grasses in native prairie, on overgrazed or mowed grasslands, in parks and golf courses, and occasionally in brushy areas bordering forests. Three subspecies occur in Kansas: Spermophilus tridecemlineatus tridecemlineatus in the northeastern quarter, S. t. texensis Merriam in the southeastern quarter and S. t. arenicola in the western half.

Reproduction:   Breeding begins in April, a week or two after emergence from hibernation. Five to 13 (usually eight to ten) young are born in the middle of May, hairless, helpless, and blind, after a gestation period of 28 days. By twelve days of age the young have discernable hair and stripes. At 21 days they start to walk and in 28 days their eyes open and they are weaned. In a month and a half the young leave the nest and soon become independent. Sexual maturity occurs at about nine months. Nipples are ten in number. Some adult females may produce a second litter later in the summer, but this is rare.

Habits:   The thirteen-lined ground squirrel is a strictly diurnal animal and is largely solitary, but may live in loose-knit colonies. Its home range is small and it forages only a short distance from its nest site. This squirrel is most frequently seen as it gallops with tail straight out behind to its hole where it dives in, calling with a trilling whistle. In a few moment sit reappears at the entrance, and, for a better view, often stands upright at the edge of its burrow to survey the intruder with its keen eyes. When undisturbed away from its den, the thirteen-lined ground squirrel walks slowly among vegetation as it searches for food a, when it stands upright to check for predators, the stripes on its back blend with the upright stalks of grass. It seldom climbs and then only on low shrubs. The burrow system of this squirrel includes an entrance which drops straight down 15-30 centimeters, and then turns horizontally for 25-50 cm. There is no dirt piled at the entrance, and if there are secondary escape exits, they are usually hidden in higher vegetation and are plugged with dirt. Trails generally lead to the main entrance. Somewhere along the tunnel system, generally at the end, is a nest chamber lined with dry grass. In other chambers are stores of seeds and other dry vegetation. During the hottest part of the summer, when food is scarce, this squirrel sometimes returns to its nest and becomes inactive for a week or so. In autumn, after accumulating large stores of fat, it enters its den for hibernation, generally in mid-October or November. After plugging the entrance, it enters its nest, which is below the frost line, curls into a ball with back upright and head tucked under its belly, and remains torpid until March or April. About every two to three weeks it arouses briefly and urinates During hibernation its body temperature is near the temperature of the nest chamber. Respiration is reduced from the usual 150 per minute of summer to three or four, while the heart beats as few as fifteen times per minute in contrast to 200-300 times per minute in normal activity. From one third to one half its body weight is lost during hibernation.

Food:   Grasses (especially in early spring), seeds, and many insects (especially grasshoppers) and other animal matter are consumed by the thirteen-lined ground squirrel. The less perishable items are carried in its cheek pouches to its underground storage chamber. Water is acquired from succulent plants, including cacti, and from metabolic water (water manufactured by the squirrel).

Remarks:   Badgers, coyotes, skunks, foxes, weasels, hawks, and snakes are some of the predators that use this animal for food. Maximum longevity of the thirteen-lined ground squirrel is four or five years.


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