Abstract
83 (40%) litters with an average of 3·42 pups and unbiased sex ratio were born of 207 couples. Fertility and litter average were higher in summer and autumn. Most females were fertilized on the 1st day spent with a male, which supports the mating-induced ovulation hypothesis. Infantile mortality was highest at birth and during the 1st 5 days of life. 26% of the pups died before weaning (day 25), i.e. an average of 1 per litter.