Friday, April 12, 2013

Native Species Profile - Thirteen-lined Ground Squirrel

Of the sixty-six  species of native mammals currently found in Michigan (or sixty-seven or sixty-eight species - depending on which list you use) very few are true hibernators.  To be considered a "hibernator" an animal must become inactive for an extended period of time and its heart rate, breathing rate, and body temperature all must lower significantly in cold weather.  Some animals that we think of as hibernators, such as black bears and chipmunks, do not actually hibernate.  Instead these animals can and do wake up and become active throughout the winter.  Our only true hibernators are bats, the Woodland Jumping Mouse (Napaeozapus insignis), Meadow Jumping Mouse (Zapus hudsonius), Woodchuck (Marmota monax), and Thirteen-lined Ground Squirrel (Spermophilus tridecaemlineatus).

A Thirteen-lined Groundsquirrel

The Thirteen-lined Ground Squirrel enters hibernation as early as September and does not emerge until April, spending between 6 and 8 months below ground.  During this time, its heart rate drops from around 200 beats per minute to 4 or 5 beats per minute.  Despite the reduced metabolic rates,a hibernating Thirteen-lined Ground Squirrel will lose up to fifty percent of its body weight.  This weight loss is not insignificant when the Ground Squirrel weighs at most 9 ounces.

A closer view - note the alternating dark and light stripes, with light spots in the dark stripes

Named after the thirteen alternating dark and light lines on its back, the Thirteen-lined Ground Squirrel is a native of shortgrass prairies throughout the central United States and Canada.  It is found from Texas in the south to Alberta, Manitoba and Saskatchewan in the north.  From east to west it ranges from Michigan and Ohio to Montana, Wyoming, and Utah.

In Mid-Michigan, the easiest place to find them is in cemeteries and parks.  They are very common in Riverside Cemetery in Mt. Pleasant.  Look for small round holes around headstones and 2 inch wide runways through the lawn.  Watch for them standing on their hind legs, with their forelegs tucked to their chest.  This posture allows them to see over the grass and keep an eye out for predators.

Thirteen-lined Ground Squirrels will often from loose colonies, each ground squirrel will have its own burrow but individuals will interact during the day.  Young ground squirrels often dig burrows near their mother, extending the size of the colony.

Like other squirrels, the Thirteen-lined Ground Squirrel is an omnivore.  It eats a variety of grasses and other green plants, seeds, insects, eggs from ground-nesting birds, and sometimes mice.  My wife has a ground squirrel that frequently visits her birdfeeders to forage for seeds on the ground.

A Thirteen-lined Ground Squirrel standing on its hind legs

Basic Information

Thirteen-lined Ground Squirrel
Spermophilus tridecaemlineatus

Size:  6-8” long

Weight: 4-9 ounces

Habitat:  open grassy areas, fields, lawns, pastures, meadows, prairies, roadsides, cemeteries

Eats:  green plants, seeds, insects, bird eggs, mice

No comments:

Post a Comment