A comparative study of sperm, sexual hormone concentration and sexual activity in yearling and adult males of the silver fox (Vulpes vulpes)
1999
Osadchuk, L.V.
The silver fox is an extreme seasonal breeder with one reproductive season during the year. Males are sexually mature at the age of 9 to 10 months. In the present study reproductive function in yearling and adult silver fox males before and during the reproductive period was examined. The aim was to determine the age-dependent features of their reproductive system. It was found that yearling males mate with a smaller number of females and that their first mating period is shorter compared with adult foxes. A high proportion of yearling males did not mate at all (27%) or their sexual activity was reduced (26%), although the number of pups born from mating males was normal. During the peak of male sexual activity, the number of spermatozoa in the ejaculate was lower in yearling compared with adult males. However, there was no difference in the number of abnormal forms of spermatozoa between the two groups. There was no significant difference in sperm numbers between sexually active and inactive yearlings. Before the reproductive season, yearling males did not differ from adults in plasma concentration of testosterone, while body and testes weights and level of oestradiol were lower. At the end of the breeding season, yearlings did not differ from adults in any trait. It is concluded that the reproductive capacity of yearling male foxes might be immature before the first breeding seasons but that this immaturity did not decrease their reproductive success.
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