Cascade golden-mantled ground squirrels are polygynous. Males emerge earlier from hibernation and then guard a territory waiting for the females to emerge and begin estrous. Males will mate with females who reside within theor territory.
Somewhat atypically, in the fall males usually enter into hibernation later than females. This is thought to be a mating strategy. In other species of ground-dwelling sciurids, males typically enter into hibernation before females, because, lacking the high energy demands of lactation, they are able to achieve adequate fat reserves early, and are less prone to heat stresses if they begin hiberation soon. In species where males enter hibernation after females, it is generally because it takes males longer than it does females to store enough food winter snacking. Spermophilus saturatus is not known to store food. It is thought that the reason for the later immergence of males is that it allows them to see where the females are hibernating, then following spring they remember where the females will be emerging when they are ready to mate.
Mating System: polygynous
Reproduction in this species is timed to coincide with emergence from hibernation. In the early spring (early April to late May), adult males emerge from hibernation. They defend territories and wait for females to emerge. Adult females emerge less than 15 days after males. Mating begins a few days after the females emerge and lasts up to two weeks. The mating season is highly synchronous, and females will birth one litter/year.
Gestation lasts only 28 days, after which the female gives birth to as many as five pups. Juveniles weigh only 6 grams and are highly altricial at birth. They develop rapidly, and first appear from the burrow about 36 days after birth. Usually three pups survive to emergence, at which point they weigh around 85 grams.
Juveniles are weaned at least one week after they emerge. For a short time after their first emergence, the mother keeps a close eye on the young and will help them back into the burrow if there is any sign of danger. However, usually by mid-July they are on their own to leave the burrow. Both sexes disperse from their natal burrow and establish their own home range. They have been found to disperse up to 300 meters from the natal burrow.
Juveniles reach adult size and sexual maturity the following spring, which is slightly less than a year after they are born. Although sexually mature, yearling females and males reproduce at lower rates than do full adults. Reproduction for adult females and males is nearly 100%, whereas it varies from 50 to 100% for yearling females. Only about 10% of yearling males breed.
Breeding interval: Cascade golden-mantled ground squirrels breed once yearly.
Breeding season: Breeding occurs from April to May.
Range number of offspring: 3 to 5.
Average gestation period: 28 days.
Average weaning age: 6 weeks.
Average time to independence: 2 months.
Average age at sexual or reproductive maturity (female): 10 months.
Average age at sexual or reproductive maturity (male): 10 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous
Average birth mass: 5.97 g.
Average gestation period: 28 days.
Average number of offspring: 4.16.
Average age at sexual or reproductive maturity (male)
Sex: male: 335 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 335 days.
Males are not involved in the parental care of this species. Females give extensive parental care to their altricial young until they are weaned. She provides the young with milk, grooming, and protection. After the young emerge from the burrow, the mother keeps a close eye on them for protection and warning, until it is time for them to disperse.
Parental Investment: no parental involvement; altricial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)