Thirteen-lined Ground Squirrel
| Scientific Name | Ictidomys tridecemlineatus |
| Survival Strategy | True hibernator |
| Begin Hibernation | October |
| End Hibernation | April |
| Conservation status | Least Concern |
Spring
Ground squirrels mate soon after they emerge from their winter burrows in late March or April and give birth in May after a gestation period of 28 days.
Summer
Young ground squirrels leave their underground nest at 5 to 6 weeks and, by eight weeks, live an independent (and hazard-filled) life. They consume a large amount of food, often doubling their springtime body weight. Much of this weight gain is brown fat (brown adipose tissue), which provides most of the energy needed to survive hibernation.
Fall
By October, ground squirrels have entered their winter burrows and are transitioning to the winter torpor state of hibernation.
Winter
The thirteen-lined ground squirrel spends the entire winter underground, occasionally coming out of torpor to eat and urinate.
Behavior
Burrows
Thirteen-lined ground squirrels forage within a few meters of an escape burrow. They dig several shallow tunnels throughout their territory, typically with only one entrance. They retreat to safety underground at the first sign of danger, such as the passing shadow of a hawk.
They will also build deeper, more complex burrows for sleeping, raising young, and hibernating. These elaborate underground homes are 4 to 6 meters (15 to 20 ft) long, with several entrances, and made of a network of tunnels and chambers below the frost line. Before hibernation, ground squirrels will seal the openings with soil.
Physiology
Hibernation is Not Sleep!
In its underground shelter, the thirteen-lined ground squirrel curls into a ball and enters a state of hibernation. Its body temperature drops to near-freezing, its heart rate drops from 200 beats per minute to around 20 beats per minute, and its breathing slows down from 150 breaths per minute to less than one breath every five minutes, using about 2% of its normal oxygen. A Thirteen-lined ground squirrel will briefly come out of hibernation about every ten days to eat stored food and urinate. At that time, its body temperature rises from 8°C (46°F) to 37°C (98°F) in less than three hours.
Avoiding Dehydration
Ground squirrels do not drink water for seven months of hibernation. They produce hormones that tell the kidneys to make less urine to avoid dehydration. They also remove salts and other compounds from the blood, preventing osmosis from moving water out of their cells and activating a thirst response in the brain. Unlike the blood of hibernating ground squirrels, movie theater popcorn has extra salt to trigger thirst and generate soda sales.
Understanding how thirteen-lined ground squirrels prevent dehydration could advance treatments for diabetes and planning for extended human space flights.
Bone Loss and Muscle Building
The inactivity of nearly six months of hibernation impacts the thirteen-lined ground squirrel’s body. It will lose up to 40% of its body weight and experience bone loss during the winter. However, it can maintain and even build muscle during hibernation, which allows it to be fully active when it emerges in the spring.
Avoiding Cold Temperature Blood Clotting
During hibernation, the thirteen-lined ground squirrel’s body temperature is around 8°C (46°F), a temperature that would cause blood platelets in most mammals to form deadly clots (hemostasis). Ground squirrels suppress this clotting for over seven months while hibernating in their burrows. When they reemerge in the spring, they must quickly restore their clotting ability to avoid lethal bleeding due to any minor injury.
Unlike in hibernating ground squirrels, human platelets form clots if exposed to cold temperatures. Medical centers must store human platelets at room temperature, which causes them to have a short shelf-life. Understanding how ground squirrels prevent hemostasis could lead to long-term storage of human platelets through refrigeration and save many patients’ lives.
Diet
Thirteen-lined ground squirrels are opportunistic omnivores. Half of the food they eat is animal matter, such as insects, mice, baby birds, and other small animals. They also eat seeds and are particularly fond of sunflower seeds that fall from bird feeders. This rodent also enjoys whatever tender plant parts are in season. Ground squirrels will learn quickly where accessible food sources are, such as garden tomatoes and birdseed bags.
Lifespan and Mortality
If they survive to adulthood, Thirteen-lined ground squirrels live for about two years.
Up to 90% of young ground squirrels die from predation before their first hibernation begins.
Predators
Predators include hawks, foxes, coyotes, badgers, and snakes.
Climate Vulnerability
There are no known vulnerabilities due to climate change at this time.
Never stop learning
Etymology: The thirteen-lined ground squirrel’s scientific name is Ictidomys tridecemlineatus. “Ictidomys” comes from the Greek iktidos meaning “a weasel” and myos meaning “mouse. “tridecemlineatus” is Latin for “thirteen-lined.
Sports: Goldy the Gopher, the mascot for the “Golden Gophers” of the University of Minnesota, is a thirteen-lined ground squirrel. (Go Badgers!)
First Nations: The Cree word for thirteen-lined ground squirrel is “sasagawaptsoos.”
References
| Animal Diversity Web: thirteen-lined ground squirrel Petrella, S. 1999. “Spermophilus tridecemlineatus” (On-line), Animal Diversity Web. https://animaldiversity.org/accounts/Spermophilus_tridecemlineatus/ |
| No-Exercise Routine: Squirrels Build Muscle While Hibernating https://www.discovermagazine.com/health/no-exercise-routine-squirrels-build-muscle-while-hibernating |
| eek!:13-lined Ground Squirrel https://eekwi.org/critter/mammal/13squirrel.htm |
| Not so nutty: Fat-burning squirrels may hold clues for future diet drugs https://www.mprnews.org/story/2014/02/10/not-so-nutty-fat-burning-squirrels-may-hold-clues-for-future-diet-drugs |
| University of Minnesota’s Evolution of Goldy the Gopher https://www.thedailygopher.com/2014/8/25/6065837/goldy-gopher-minnesota-evolution-history |
| Hohn, E. Otto. “Mammal and Bird Names in the Indian Languages of the Lake Athabasca Area.” Arctic, vol. 26, no. 2, 1973, pp. 163–171. JSTOR, www.jstor.org/stable/40508379. |
| Here’s how hibernating squirrels live for months without water https://www.science.org/content/article/here-s-how-hibernating-squirrels-live-months-without-water |
| Cooper, Scott T et al. “The hibernating 13-lined ground squirrel as a model organism for potential cold storage of platelets.” American journal of physiology. Regulatory, integrative and comparative physiology vol. 302,10 (2012): R1202-8. doi:10.1152/ajpregu.00018.2012 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3362150/ |
| Cleary, Edward C. and Craven, Scott R., “Thirteen-Lined Ground Squirrels” (1994). The Handbook: Prevention and Control of Wildlife Damage. 24. https://digitalcommons.unl.edu/icwdmhandbook/24 |