| Summary: | The locomotor activity of the reindeer is separated into a diurnal and a nocturnal phase which, in turn, consists of a number of short-term activity bursts. The onset and termination of diurnal and nocturnal activity are largely in synchrony with sunrise and sunset. Since the diurnal phase is longer, total activity is dependent on the photoperiod. Total activity as well as the number of activity bursts is greater in Jùne with continuous daylight than in December with 6 hours daylight. In winter, reindeer spent less time feeding but more time ruminating and resting *than in summer. Synchronization between individuals was also greatest in winter. It is concluded that the described changes in the activity pattern are due to an endogenous component and that this component further controls food consumption and energy balance of the reindeer. Seasonal variations in behavioural patterns are described. Several specific rutting behavioürs, sexual and agonostic, emerge in the male during the prerut and persist until after the rut. The preorbital gland is enlarged and secretory activity is evident. The rut is cha'tabterized by the sudden appearance of an odour in the breath of mature males followed a few later by a strong odour in the urine. These odours persist for a short time during the most intense period of rut. The amount of androgen rizes sharply and reaches peak concentrations in late September - early October, decreasing thereafter. The described behavioural cues occur with a certain constancy in time in concecutive seasons. A quantification of the amounts of secretory epithelia in preorbital, interdigital, caudal and tarsal glands reveals that only the preorbital gland is subjected to any seasonal and sexual variation. The apocrine epithelium in this gland is most developed in mature males during the rutting season and seems to be dependent upon the presence of an elevated androgen concentration. The tarsal gland is the least developed gland while the interdigital and caudal glands are more welldeveloped and ...
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