Testes mass and gonadosomatic index lower in juveniles than in older wolves.
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Testes mass positively correlated to body mass.
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The probability of fertility increased with testes mass.
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Cryptorchidism was found in about 5% of the male wolves.
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Sperm production was evident in 41.8 % of wolves < 1 year of age.
Abstract
Improved knowledge about reproductive patterns and potential in male wolves (i.e., testicular development and size relative to age, pubertal age, and seasonal effects) is needed for evaluation and monitoring of reproductive outcomes in populations. Reproductive organs from 215 male wolves, culled as a result of licensed hunting, protective culling or from carcasses found were examined. The testes and epididymis were weighed and measured. There were biopsy samples collected from the testes and the cauda epididymis for histological determinations if there were spermatozoa in tissues collected. There were reproductive tissue analyses of 197 males while there were separate evaluations of tissues from ten cryptorchid animals. Juvenile wolves (< 1 year, n = 47) had a lesser body mass and mean testes mass than subadult (1–2 years, n = 71) and adult (>2 years, n = 79) males. Season also affected testicular characteristics of structures evaluated with subadult and adult males having a lesser mass during summer months (May–August). Of the 197 males, 70 % had spermatozoa in the seminiferous tubules and the cauda epididymis and were classified as being ‘potentially fertile’ when tissues were collected, while 22 % were classified as being non-fertile (no spermatozoa, including males that were pre-pubertal) and tissues of 8% could not be evaluated. When testes mass was greater, there was a greater likelihood that spermatozoa were present. There were seven of the ten cryptorchid males of the unilateral type. These testicular and epididymal findings will be useful for evaluating the reproductive potential and management of wolves in Scandinavia.
