The effects of luteinizing hormone, oestrogen and ovariectomy on the agonistic behaviour of female Quelea quelea

Previous work with male Quelea showed that agonistic behaviour in relation to individual distance is controlled by luteinizing hormone (LH), rather than by testosterone, and that males are more aggressive than females. Experiments with female groups are reported which show that: (a) LH injections increase aggressive encounter frequency; (b) ovariectomy in the breeding season (but not outside it) also increases encounter frequency; and (c) oestrogen injections decrease encounter frequency. The effects of LH were shown to be specific to agonistic responses rather than mediated through changes in activity. Correlations between changes in natural hormone levels and encounter frequency support the injection findings. These results are consistent with the hypothesis that LH controls aggressive encounters over individual distance in the female as in the male and that oestrogenic inhibition of this LH-mediated aggressiveness is a cause of female subordination and the lower encounter frequency found in female groups. The annual cycle of encounter frequency is described and the significance of different systems of hormonal control is discussed.