Anirn.Behav., 1973,21, 557-563 PREDICTORS OF DOMINANCE IN THE MALE GOLDEN HAMSTER (MESOCRICETUS AURATUS) BY LEE C. DRICKAMER, JOHN G. VANDENBERGH & DAVID R. COLBY Research Division, North Carolina Department of Mental Health, Raleigh, North Carolina Abstract. The outcome of social interactions between four male hamsters was significantly related to body weight (rs=0.66) and to the size and pigmentation of their lateral flank glands (r,=0.82). Weight was held constant in a second experiment and variations in gland size and pigmentation remained significantly related to the outcome of social encounters (rs=0.77). In a third experiment, castrate hamsters of uniform weight receiving either no hormone, 0.1 mg, 0.50 rag, or 1.00 mg testosterone propionate exhibited flank gland variations significantly related to social rank (r,=0.81). These experi- ments demonstrate that the state of the flank gland, which is related to endogenous androgen levels, can be used as a predictor of social rank in male hamsters. In male rabbits the weight of the anal and inguinal glands shows a significant positive linear relationship with position in a social hierarchy (Mykytowycz & Dudzinski 1966). Similarly in the marmoset, the amount of scent marking with the sternal gland correlates positively with social status (Epple 1970). In these studies and in a similar examination of the marking be- haviour of the golden hamster (Johnston cited in Rails 1971), the measurements of glands or scent marking behaviour have been post hoc, that is, the social hierarchy of the animals was determined by observation, then gland measures were taken. In assessing factors which may determine or affect dominance status in small mammals three factors are most often tested: (1) experi- ence, (2) body weight, and (3) hormones. In the golden hamster Payne & Swanson (1970) have shown that weight is an important factor in determining the winner of agonistic encounters. In our experiments with male hamsters we have tested the importance of both body weight and the size and pigmentation of the lateral flank glands as predictors of social status in groups of four animals. To achieve this goal three experiments were conducted. Experiment I This experiment was designed to assess the importance of: (1) body weight and (2) flank gland size and pigmentation in predicting social status among intact, adult male golden hamsters. Methods Twenty-four 100- to 170-day-old male hamsters were assigned at random to six groups of four animals each with the restriction that the maxi- mum age difference within any group of four was 10 days. The hamsters were housed in- dividually from weaning at 21 days of age until the experiment began. The behavioural observations were conducted in a 1.1 x 2.2-m plywood pen with walls 0.5 m high to prevent escape. The pen was divided into four equal-sized compartments each having 1.1 x 0.55 m of floor-space. Two brick baffles and a 45-cm high climbing-pole in each com- partment increased the complexity of the en- vironment. Food and water were available in all compartments. Each compartment was con- nected to the two adjoining compartments by a sliding, metal door. All experimental hamsters and the observation pen were housed in a room maintained at 22 ~ to 26~ and 20 to 70 per cent R.H. The light cycle consisted of 14 hr of bright light (day) and 10 hr of dim light (night). The golden hamster (Mesocricetus auratus) possesses paired lateral sebaceous glands on the rear flanks (Fig. 1). By clipping the fur in this region the gland can be exposed for measure- ment. The demonstrated androgen dependence of these flank glands (Hamilton & Montagna 1950; Vandenbergh 1973) was confirmed by the present investigation. Castration of the male hamster results in a reduction in both size and pigmentation of the flank gland. Hormone replacement with testosterone propionate re- stores the size and pigmentation (Plate X, Fig. 1). Each of the six groups of four hamsters were exposed to the same experimental procedure. The hamsters were weighed and the size and reflectance of the flank glands were measured (see section on flank gland index below). As 557