More info for the terms: litter, monoestrous, parturition, polygamous
Wolverines are sexually dimorphic. Adult males average 24 to 61 pounds (10.9-27.5 kg), while adult females average 15 to 41 pounds (7-19 kg) [50,64,69,75,91]. The skull and teeth of wolverines are more robust than those of other carnivores of similar size. Wolverines are capable of eating frozen meat and crushing bones of large prey including deer (Odocoileus spp.), caribou (Rangifer tarandus), and moose (Alces alces) ([46], reviews by [50,85]).
Wolverines are solitary [85]. While they are primarily nocturnal [46,55], they also travel during daylight hours [7,46]. Wolverines are active year round [10,54,64,75,115]. Rather than maintaining territories, wolverines scent mark to advertise their current positions [54]. Individual home ranges may overlap extensively with those of other individuals [10,54].
Males and females reach sexual maturity at 2 to 3 years of age [10,13,91]. Some males reach sexual maturity at 14 to 15 months of age [91]. Occasionally, females produce litters as yearlings [10,13,91]. Most females produce litters every 2 to 3 years [31,54,64]. Physical condition and age may be a factor in whether females reproduce each year [31,87].
Rausch and Pearson [91] speculated that wolverines are polygamous. Observations of the breeding biology of wolverines suggest that females are monoestrous [13,90,91]. The mating season spans April to August, with a peak in late May and June [64,91]. Male breeding condition peaks April to June. Delayed implantation typically occurs in late January or early February [91,124], but may happen anytime from November through March [10,13,91].
Parturition (births) occurred 215 to 272 days after copulation in captive wolverines [81]. Active gestation lasts 30 to 40 days [91]. Births peak February to March [46,77,85,90,91], but may occur at any time from January through April [31,75,90,91]. Wolverine parturition may correspond with periods when carrion is most abundant [91], such as caribou calving season [29].
Litter sizes range from 1 to 6 kits per litter, with an average of 2.2 to 3.0 kits per litter [46,54,90]. Average litter size for females in northwestern Alaska was 1.75 kits after dens were abandoned. This did not include newborn mortality [75].
Kits are weaned by 10 weeks of age [31,64] and remain with their mothers up to 2 years [64,112]. The average dispersal age for males and females in Scandinavia was 13 months [112].
According to a review, average annual survival may range from 0.80 to 0.975 [11]. More recent studies have recorded survival rates that deviate slightly from the range. Average first-year survival for juveniles in Scandinavia was 0.68 [88]. Average annual survival in Idaho and Montana was 0.80 excluding licensed trapping, and 0.57 including licensed trapping [105]. In a 12-study synthesis, overall annual survival for all age and sex classes in untrapped populations was >0.84. Overall annual survival for all age and sex classes in trapped populations was <0.75 [62].
Average life expectancy of wild wolverines in Montana is 4 to 6 years, with few exceeding 8 years of age according to unpublished data by Hash [50]. According to a review, wild wolverines may reach 8 to 10 years old [57]. The oldest wolverine examined by Rausch and Pearson [91] in Alaska and the Yukon Territory was a 13-year-old female.