SEX-RATIO VARIATION AND MATERNAL INVESTMENT IN RELATION TO SOCIAL-ENVIRONMENT AMONG FARMED SILVER-FOX VIXENS (VULPES-VULPES) OF HIGH COMPETITION CAPACITY

The sex ratio and body weights of offspring from 13 non-infanticidal f armed silver-fox vixens oi high-competition capacity (HCC), reared und er two different neighbouring conditions, were measured. Seven vixens had other HCC vixens as neighbours, whereas the other group had neighb ouring vixens of low-competition capacity (LCC). The vixens with LCC n eighbours gave birth to and weaned more cubs, with a significantly hig her proportion of males (73%), and female cubs of a relatively better HCC neighbours (31% males, female cubs on average 79 g lighter than th eir brothers). This study indicates sex-ratio regulation in relation t o social environment among farmed silver-fox vixens of high-competitio n capacity. The results are discussed in relation to the future behavi oural and reproductive consequences tor the female cubs.