Influence of age, nutritional status and season on the reproductive system in wild male mink (Neovison vison)

摘要

The objectives of this study on the reproductive system of wild male mink (Neovison vison) were to determine the influence of age, nutritional status and season on reproductive traits and to produce baseline data that may be used in environmental monitoring programmes. The 117 male mink included in the study were killed by hunters all over Sweden (from latitude 56° N to 67° N) during August to the end of April from 2005 to 2008. The weights of penis, testes, and epididymides were lower, the anogenital distance was shorter and the diameter of seminiferous tubules was less in juveniles compared with adult mink (p<0.0001-p=0.0024). There was a positive effect (p<0.05) of nutritional status on the baculum length and on the anogenital distance, but noton any of the other reproductive traits. The season of sampling influenced the penis, testes and epididymes weights and the diameter of seminiferous tubules (p=0.008-p<0.0001). During spring, 86% of themink had sperm in their epididymides, whereas the corresponding figure for autumn was 3%; in addition, when the average diameter of the tubules reached 138 im, sperm were present in the epididymides. Sperm morphology was analysed in 29 of the mink, andthe percentage of morphologically defect sperm were generally low. Taken together, this study suggests that when assessing male reproductive data in wild mink populations, season must be taken into account as well as whether the individuals are juvenileor adult. In contrast, the nutritional status seems not to be of any major significance.