Northern Prairie Wildlife Research Center
The following reproductive parameters were documented for the swift fox (Vulpes velox) in captivity: mean litter size (2.9+/- 0.16 offspring) and even sex ratio (1:1) at birth, age-sex specific fertility, age of puberty (10 months in each sex), reproductive longevity to date in females (six years) and males (10 years), mean breeding date (9 March +/- 0.31 d). Observations on mating behaviors, partner compatibility and parental care are noted.
Several hypotheses are proposed and tested using data in the swift fox studbook. No correlation was found between litter size and gestation or birth seasonality. Multiparous females are correlated with early births, short gestation, increased age and low infant mortality compared to primiparous females. Litter size does not vary with parity, nor does it influence infant mortality. Infant survival to six months post partum is 81%. Mortality is not significantly different between age-sex classes.
An age-sex specific life table is presented. Mortality rate (Qx) in the 0-1 age-sex class is high; reproductive values (Vx) are highest in ages two, four, and five in both sexes. Net reproductive rate (R0) per generation in the captive population ranges from 1.6906 (males) to 2.0563 (females). Mean generation time in captivity varies from 3.57 (males) to 4.11 (females) years.
Well maintained wild animals studbooks offer opportunities to obtain insights into reproductive strategies of species that may be difficult to obtain under field conditions.