Certain Aspects of Reproduction in a Herd of Silver Foxes

Abstract

Observations extending over a period of 14 yrs. were subjected to statistical analysis. The mean mating date for adult foxes was Feb. 12; yearlings mated 8 days later. Additional age differences were found in time of estrus, duration of copulation, maximum vulvar size, and failure to mate. Individual differences, persistent over several years, were tendency to mate in same part of breeding season, duration of copulation, vulvar size during proestrus, tendency to destroy litters, and size of litters whelped by adults. Of uncertain individual expression were failure to mate and to whelp. Elimination of yearlings showing undesirable characters would thus improve the herd as long as the selected individuals were maintained. Possible genetic improvement following selection was not investigated.