Seasonal Changes in the Testicular Blood Flow of Seasonally Breeding Mammals: Dormouse, Glis Glis , Ferret, Mustella Furo , and Fox, Vulpes Vulpes

Summary. The testicular capillary blood flow of three seasonally breeding mammals has been measured, using the radioactive inert gas clearance technique at approximately monthly intervals throughout the year. Mean blood-flow values±S.E.M. (ml/min/100 g) recorded in seven dormice were minimal (18·3±1·2) from December to February and maximal (41·6±1·7) in June; in eight ferrets, they were minimal (21·3±1·5) in July and maximal (35·2±2·1) from January to March; in thirteen foxes, they were minimal (21·3±2·1) from May to September and maximal (68·3±3·6) in January. The seasonal patterns of testicular capillary blood flow vary greatly between species: they are more obvious in the fox and dormouse. In these two species, the seasonal morphological modifications of the testes are more important. The testicular capillary blood flow is maximal when the testes are in an active state and minimal during the inactive period.