Does fear of humans by silver fox affect reproductive performance and cub behaviour?

Abstract

Earlier experiments indicate that the silver foxes’ fear of humans is reduced with use of food titbits. Sex ratio, growth and behaviour were examined in cubs from multiparous silver fox vixens, which either received a titbit twice a week during pregnancy (Gl, n = 14), or received the same amount of human contact without any titbit (G2, n = 14). The cubs were tested in an open field ( 1.15 m X 1.15 m area divided into a 5 x 5 square grid) at 30 days of age, in the early stages of primary socialisation. Cub activity was recorded (number of grid lines crossed (Lc) during 3 min). There was no difference due to treatment in the number of cubs born or cubs weaned at 49 days (4.9 f 0.3 and 4.1 f 0.4 vs. 4.8 f0.5 and 3.8* 0.4 for Gl and G2, respectively; NS). However, the Gl vixens delivered a significantly higher proportion of male cubs than G2 (64% 6 vs. 5 1% 0, P < 0.05; Gl , 3.1 k 0.48, 1.8 k 0.3 0 ; G2, 2.5 f 0.48, 2.3 + 0.3 P ). Female cubs from Gl were more active in the open field (Gl, 51.4k4.8Lc; G2,34.2*4.7Lc; P<O.O5), and heavier at 49 days of age (Gl, 1660*42 g; G2, 149 1 rt 40 g; P < 0.01) than female G2 cubs. No significant differences in activity or liveweight were found for male cubs (activity: Gl, 46.4& 3.4Lc, G2, 37.1 f4.3Lc; NS; weight at 49 days; Gl CT, 17 16 f 29 g; G2 0, 1729 f 37 g, NS). Reduced fear of humans during pregnancy affected the sex ratio in the litter, and growth and activity of female cubs in the silver fox. 0168-1591/95/$09.50