Spermophilus richardsoniiRichardson's ground squirrel

Geographic Range

Spermophilus richardsonii is found in central Alberta and western Montana to western Minnesota.

Habitat

Richardson's ground squirrel lives in areas of open plains with short grasses. The animal also spends large amounts of time in the soils of these areas in burrows. The animal avoids heavily forested areas.

Physical Description

Total body length for Richardson's ground squirrels is from 283 to 337 mm in males and 264 to 318 mm in females. Tail length varies from 65 to 88 mm in males and 55 to 82 mm in females. Pre-hibernation males ranged in weight from 440 to 745 g, and from 290 to 500 grams post-hibernation. Pre-hibernation females ranged from 330 to 590 grams and from 120 to 290 grams post-hibernation . They are dark brown along the top of the body and lighter brown on the sides with a whitish underbelly. The tail is short and covered with fur, but is not bushy.

  • Average mass
    342.5 g
    12.07 oz
    AnAge
  • Average basal metabolic rate
    0.788 W
    AnAge

Reproduction

Females are monestrous and have one litter per year. Mating takes place soon after hibernation ends, from late March to early May. Intense male competition for access to females occurs during the mating period. Each females is receptive for only about 3 hours but will mate with several males during that time. As soon as a female is impregnated she becomes aggressive towards males. Females prepare nest chambers where their litter will be born and reared. Gestation lasts for 23-31 days and litters are typically 6 to 8 young. The young are weaned at 4 to 6 weeks of age. The young reach adult size and sexual maturity at about 11 months. Females live for 2 to 4 years, sometimes living as long as 6 years. Male Richardson's ground squirrels rarely live longer than two years as a direct result of energetic expense and mortality associated with male-male competition during mating.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    6.06
    AnAge
  • Average gestation period
    24 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    335 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    335 days
    AnAge

Behavior

Richardson's ground squirrels construct complex burrows, reaching from 3.5 to 15 meters in length, 75 mm in diameter, and .75 to 2 meters deep. There are several chambers and an average of 8 entrances to the burrow system. The main entrance is marked with a mound of dirt.

Richardson's ground squirrels hibernate for seven months each year, from September or October to April or May. During hibernation, these animals live off fat reserves they accumulate during the active portion of the year.

After emerging from hibernation, males establish territories of about .058 ha. This area usually encompasses 3 to 5 female burrows. After mating has occurred, females establish their own territory which averages .016 ha within the male's territory. The female's territory remains the same each year, being passed on from mother to daughter.

S. richardsonii has three daily activity periods, during the first two hours after sunrise, the hours between 10:00 AM and 2:00 PM, and from 4:00 PM until sunset.

Communication and Perception

Food Habits

The diet of S. richardsonii consists of seeds, nuts, grains, bulbs, green vegetation, insects and other types of small invertebrates. Food is stored in the burrow, but is eaten only after awakening from hibernation.

Economic Importance for Humans: Positive

Richardson's ground squirrels are important members of their ecosystems, acting to recycle soil nutrients and providing an important source of prey for many predator species, they are also available as pets.

Economic Importance for Humans: Negative

Richardson's ground squirrels carry fleas that transmit the bacterial disease bubonic plague. They have also been known to cause the spread of tularemia and Rocky Mountain spotted fever. Richardson's ground squirrels are a major agricultural pest in Canada and the northern United States, they can cause massive crop destruction.

Conservation Status

Due to the clearing of forests for farm land, the natural habitat and population size of S. richardsonii has increased dramatically.

Other Comments

Owners of Richardson's ground squirrels seem to agree that the creatures make very nice pets. The animal enjoys chewing on furniture and curtains, however, some claim that the squirrels can be trained by tapping them on the nose when they misbehave. Pet distributers recognize the importance of exercise and ask all pet owners to keep a wheel in the cage. The animals enjoy being played with and petted frequently.

Contributors

Sandra Bruening (author), University of Michigan-Ann Arbor, Sandra Bruening (author), University of Michigan-Ann Arbor, Cynthia Sims Parr (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Accessed November 20, 1999 at www.nature.ca/notebooks/english/richgrds.htm.

Accessed November 19, 1999 at www.cadvision.com/rothermj.

Michener, G. 1985. Chronology of reproductive events for female Richardson's ground squirrels.. Journal of Mammalogy, 66: 280-288.

Nowak, R. 1999. Walker's Mammals of the World 6th ed. Vol II. Baltimore: The John Hopkins University Press.