Males emerge from hibernation before females and compete for access to females as they emerge. Once mating is completed, there is no further interaction between males and females.
Mating System: polygynous
Only one litter per year is produced due to the small amount of time S. washingtoni are active above ground (Verts and Carraway, 1998). Litter size ranges from five to eleven (Verts and Carraway, 1998) and an average of eight embryos was found in a sample of 26 S. washingtoni (Hayssen et al., 1993).
The reproductive season begins in January and sometimes lasts through April. Breeding occurs in late January and early February (Verts and Carraway, 1998). Young are birthed in late February and March in Washington and mostly in March in Oregon (Hayssen et al., 1993).
Spermophilus washingtoni reaches sexual maturity early and first breed as yearlings (Verts and Carraway, 1998).
In 1941, T. Scheffer reported that S. washingtoni are polygamous, but little else has been reported on mating behavior or parental care.
Breeding interval: Breeding occurs once yearly.
Breeding season: Breeding occurs in late January and early February.
Range number of offspring: 5 to 11.
Average weaning age: 1 months.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
The young are birthed underground in burrows and emerge by March (Hayssen et al., 1993). They are altricial and at birth their eyes and ears are closed and no teeth have erupted. However, development is rapid and within 10 days head and body hair is present. After about 15 days the incisors erupt, and the eyes open within 20 days (Tomich, 1982). In late March, when about 1 month old, babies weigh from 22 to 44 grams (Hayssen et al., 1993) and average 38.8 grams (Verts and Carraway, 1998). Weaning takes place in the first month, and after one month no milk curd is found in the stomachs of some captured individuals (Verts and Carraway, 1998). By late April, the average mass is 116 grams (range: 89 - 139 grams). The mass by late May ranges from 147 to 205 grams. The male ranges from 175 to 205 grams and the females ranges from 147 to 193 grams.
Males do not care for young.
Parental Investment: altricial ; pre-fertilization (Provisioning); pre-hatching/birth (Provisioning: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)