Urocitellus richardsonii (Sabine, 1822)

Adult Length

Adults of Urocitellus richardsonii, commonly known as Richardson's ground squirrel, typically reach around 30 centimetres (12 inches) in total length.

Weight Variation Factors

Their body weight changes dramatically based on season and location.

Post-Hibernation Weight

When they first emerge from hibernation, females weigh between 200 and 275 grams (0.441–0.606 pounds), while males weigh between 350 and 450 grams (0.77–0.99 pounds).

Pre-Hibernation Weight

By the time they re-enter hibernation, their weight can increase to nearly 750 grams (1.65 pounds).

Sexual Size Dimorphism

On average, males are slightly larger and heavier than females.

Fur Coloration

This species has dark brown fur on its upper body and tan fur on its underbelly.

External Morphology

Compared to other ground squirrels, its tail is shorter and less bushy, and its external ears are so short that they appear more like small holes on the head.

Behavior Comparison

The behavior of Richardson's ground squirrel is more similar to that of a prairie dog than a typical ground squirrel.

Common Nickname Origin

Its tail trembles constantly, which gives the species the common nickname "flickertail".

Wild Life Expectancy

Average life expectancy differs by sex: males live an average of 3 years, while females live an average of 4 years.

Captive Lifespan

Individuals held in captivity may live between 5 and 7 years.

Native Range

This species is native to short grass prairies, and is found mainly in northern U.S. states including North Dakota and Montana, as well as western Canada including central and southern Alberta, southern Saskatchewan, and southern Manitoba.

Range Expansion

Its native range has expanded as forests were cleared to create farmland.

Suburban Habitat Adaptation

It is not limited exclusively to prairie habitats; it sometimes adapts to live in suburban environments, where it is often considered a pest because of the burrows it digs.

Urban Burrowing Behavior

It is not uncommon to find these squirrels digging tunnels under the sidewalks and patios of urban homes.

Reproductive Frequency

Female Richardson's ground squirrels produce one litter per year.

Litter Size

The average litter size is 6 individuals, and the largest recorded litter size is 14.

Birth Period

Offspring are born in April or May.

Juvenile Emergence Timeline

Young squirrels stay underground in the natal burrow until they are approximately 30 days old, emerging from the burrow from late May to mid-June.

Juvenile Emergence Weight

When they first emerge, young squirrels weigh between 50 and 100 grams.