Reports regarding the mating system of this species are variable. The weight of evidence seems to support the conclusion that sagebrush voles are monogamous.
Mullican and Keller (1986) reported that these animals live in male-female pairs in the wild, indicating a monogamous existence. One captive study confirmed that males and females share a single nest during the post-partum period, as is common for monogamous microtine rodents (Hofmann, et al., 1989). In species known to be polygynandrous, males inhabit separate nests. Also, in their breeding colony, pups often continued to inhabit the parental nest when another litter was born. This supports the notion that local concentrations of animals seen in the wild represent extended families, living in a somewhat colonial fashion.
However, not all of the data collected by Hofmann, et al (1989) were consistent with a monogamous breeding system. They also showed that males and females did not coordinate their activity to ensure that at least one parent was always with the pups, as has been reported for monogamous species. Further, males spent very little time caring for the pups, which is uncommon for monogamous species, and is very common in polygynous species. Further research is needed to clarify the mating system of this rodent.
Mating System: monogamous
Sagebrush voles breed year round, although in the northern portion of their range they generally breed only from March to early December. The estrous cycle of sagebrush voles is approximately 20 days, and within 24 hours after giving birth, a postpartum estrus occurs. A litter of 5 is average, with a range from 1 to 13. Gestation usually lasts between 24 to 25 days. Captive members of this species have been known to produce 14 litters in one year, but in the wild average 2 to 3 litters per year. Females in the wild may live together while raising young, or males and females may nest together.
Young are born naked and blind in an underground nest chamber composed of leaves, shredded sagebrush bark, and grass stems. At birth, young weigh approximately 1.5 grams. They open their eyes at 11 days, and by 21 days they are usually self-sufficient. (Brylski and Harris, 2001; Nowak, 1999)
Males may be aggressive, particularly during breeding. Sexual maturity for females is reached around 60 days, and for males between 60 and 75 days. (Brylski and Harris 2001; Hofmann et al. 1989; Nowak, 1999)
Breeding season: Lemmiscus curtatus breeds throughout the year, although in the northern part of its range, breeding may be confined to the period between March and December.
Range number of offspring: 1 to 13.
Average number of offspring: 5.
Range gestation period: 24 to 25 days.
Average weaning age: 21 days.
Range age at sexual or reproductive maturity (female): 60 to 75 days.
Range age at sexual or reproductive maturity (male): 60 to 75 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
The young are altricial. In captivity, both male and female care for the young. Because males and females have been reported to nest together in the wild (Mullican and Keller, 1986), this probably occurs in wild populations also. Hofmann, et al. (1989) showed that females generally spent more time alone in th nest than did males. They also groomed pups more frequently than did males. Frequency of grooming the pups decreased as the pups aged.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Provisioning: Female, Protecting: Male, Female)