The thirteen-lined ground squirrel (''Ictidomys tridecemlineatus''), also known as the striped gopher, leopard ground squirrel, squinney, (formerly known as the leopard-spermophile in the age of

Audubon The National Audubon Society (Audubon; ) is an American non-profit environmental organization dedicated to conservation of birds and their habitats. Located in the United States and incorporated in 1905, Audubon is one of the oldest of such organ ...

), is a

ground squirrel Ground squirrels are members of the squirrel family of rodents (Sciuridae), which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known ...

that is widely distributed over grasslands and prairies of North America.

Description

It is brownish, with 13 alternating brown and whitish longitudinal lines (sometimes partially broken into spots) on its back and sides, creating rows of whitish spots within dark lines.

Taxonomy

This species has usually been placed in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Spermophilus ''Spermophilus'' is a genus of ground squirrels in the Sciuridae, squirrel family. As traditionally defined the genus was very species-rich, ranging through Europe, Asia and North America, but this arrangement was found to be paraphyletic to ...

'' with about 40 other species. As this large genus is

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

prairie dog Prairie dogs (genus ''Cynomys'') are herbivorous burrowing ground squirrels native to the grasslands of North America. Within the genus are five species: black-tailed, white-tailed, Gunnison's, Utah, and Mexican prairie dogs. In Mexico, p ...

marmot Marmots are large ground squirrels in the genus ''Marmota'', with 15 species living in Asia, Europe, and North America. These herbivores are active during the summer, when they can often be found in groups, but are not seen during the winter, w ...

s, and

antelope squirrel Antelope squirrels or antelope ground squirrels of the genus ''Ammospermophilus'' are sciurids found in the desert and dry scrub areas of south-western United States and northern Mexico. They are a type of ground squirrel and are able to resist ...

s, Kristofer Helgen and colleagues have split it into eight genera, placing the thirteen-lined ground squirrel in ''

Ictidomys ''Ictidomys'' is a North American genus of rodent in the squirrel family, which contains the thirteen-lined ground squirrel, the Mexican ground squirrel, and the Rio Grande ground squirrel. These species were included in the species-rich ground ...

'' with two other species.

Behavior

The thirteen-lined ground squirrel is strictly diurnal and is especially active on warm days. A solitary or only somewhat colonial hibernator, it often occurs in aggregations in suitable habitats. In late summer, it puts on a heavy layer of fat and stores some food in its burrow. It enters its nest in October (some adults retire much earlier), rolls into a stiff ball, and decreases its respiration from between 100 and 200 breaths per minute to one breath about every five minutes. It emerges in March or early April. The burrow may be long, with several side passages. Most of the burrow is within one to two feet (about half a meter) of the surface, with only the hibernation nest in a special deeper section. Shorter burrows are dug as hiding places. This ground squirrel's home range is two to three acres (0.8 to 1.2 ha). Groundsquirrel4-300

Its primary diet includes grass and weed seeds,

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...

grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...

s, and

cricket Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by striki ...

s, but it may also eat mice and shrews; it will viciously attack and consume

cicada The cicadas () are a superfamily, the Cicadoidea, of insects in the order Hemiptera (true bugs). They are in the suborder Auchenorrhyncha, along with smaller jumping bugs such as leafhoppers and froghoppers. The superfamily is divided into two ...

s if able to catch them. This squirrel sometimes damages gardens by digging burrows and eating vegetables, but also devours weed seeds and harmful insects. It is well known for standing upright to survey its domain, diving down into its burrow when it senses danger, then sometimes poking out its nose and giving a bird-like trill. The "trill" is an alarm call that is most often used by females to warn nearby relatives. It has a maximum running speed of and reverses direction if chased.

Physiology

Thirteen-lined ground squirrels can survive in hibernation for over six months without food or water and special physiological adaptations allow them to do so. During

torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...

, these squirrels maintain hydration by redistributing and storing

osmolytes Osmolytes are low-molecular weight organic compounds that influence the properties of biological fluids. Their primary role is to maintain the integrity of cells by affecting the viscosity, melting point, and ionic strength of the aqueous solution. ...

like sodium, glucose, and blood urea nitrogen in different body compartments (to be identified). When they enter a transient active-like state, small periods of arousal where these squirrels return to an active-like state temporarily, osmolarity and

antidiuretic hormone Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travel ...

levels rise while thirst remains suppressed. Thirteen-lined ground squirrels also suppress the cell cycle and control the expression of cell cycle regulators in the liver during hibernation to conserve energy. Moreover, they are able to maintain their muscle contractile performance during hibernation. Although scientists determined that there is a reduction in the squirrels' muscle mass during torpor, this does not significantly change the muscles' contractile properties.Hindle AG, Otis JP, Epperson LE, Hornberger TA, Goodman CA, Carey HV, Martin SL. Prioritization of skeletal muscle growth for emergence from hibernation. J Exp Biol. 2015 Jan 15;218(Pt 2):276-84. doi: 10.1242/jeb.109512. Epub 2014 Dec 1. PMID: 25452506; PMCID: PMC4302166. During hibernation, thirteen-lined ground squirrels prioritize

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

tissue for maintenance and potential regrowth. They also increase their muscle

antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...

capacity during torpor to protect tissue from

oxidative damage Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal r ...

associated with the restoration of blood flow during the transition period from torpor to arousal. During hibernation, they mobilize

fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...

for fuel instead of

glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one o ...

, which is kept constant during hibernation.Rob S. James, James F. Staples, Jason C. L. Brown, Shannon N. Tessier, Kenneth B. Storey; The effects of hibernation on the contractile and biochemical properties of skeletal muscles in the thirteen-lined ground squirrel, Ictidomys tridecemlineatus. J Exp Biol 15 July 2013; 216 (14): 2587–2594. doi: https://doi.org/10.1242/jeb.080663 During their active-like state, they are able to resume their cell cycle.

References

External links

Thirteen-lined Ground Squirrel Genome Project page at GenBank

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Ensembl Ensembl genome database project is a scientific project at the European Bioinformatics Institute, which provides a centralized resource for geneticists, molecular biologists and other researchers studying the genomes of our own species and other v ...