Seasonal Changes of the Testicular and Thyroid Functions in the Badger, Meles meles L.

Abstract

The european Badger is a nocturnal underground mammal with a reduced general locomotor activity during winter. The plasma testosterone and thyroxine levels present marked seasonal variations (MAUREL et al., 19 77). At the end of summer and in autumn, plasma testosterone concentrations are low, while the plasma thyroxine level is high. The resumption of testicular activity takes place in December at the beginning of the phase of hypoactivity of the thyroid gland. From February to May, the plasma testosterone concentration remains at a high level; then after a rapid decrease there is an other peak in June. In summer, the plasma testosterone level decreases continuously, while thyroid activity is more pronounced. The biphasic annual rhythms occur annually, although in the location of the maximal testicular and thyroid activity.