This thesis examined the relationships between gonadal hormones and intra-specific aggressive behaviour in the house mouse (Mus musculus L.) and the golden hamster (Mesocricetus auratus Waterhouse). A literature review concerning gonadal hormones and aggressive behaviour and a discussion of relevant semantic problems associated with familiar terms such as 'aggression' and 'pheromone' were presented. Experiments were described which differentiated 'motivational' (i.e. direct effects on brain function) and 'somatic' (i.e. modulation of sensory cues) effects of hormones on behaviour. Results indicated that androgens had a more pronounced motivational effect on male aggressiveness in mice than in hamsters. However, aggressive motivation in male mice was not immediately related to levels of circulating androgen, but a complex relationship involving temporal, social and environmental factors prevailed. Isolated female hamsters were aggressive but similarly housed female mice were not. However, aggressive responses were induced in adult, ovariectomized mice by chronic administration of androgen without prior treatment in a perinatal 'critical period'. Androgen-dependent olfactory signals, which can elicit aggressive responses from conspecifics, were detected in urine from male mice. Male hamsters also produced androgen-dependent cues with similar effects, but the modality and source of such signals remained undetermined. Olfactory signals, which can reduce aggressive responses and elicit sexual behaviour from males, were also detected in urine from female mice. These signals were independent of ovarian control, but could be attenuated by androgen treatment. Vaginal secretions from hamsters contained similar cues. It was concluded that the olfactory signals identified did not 'inhibit' or 'release' stereotyped responses, but receiving animals react flexibly to identical cues according to social status and previous experience. Furthermore, a close correlation between high levels of aggressive motivation, male gender and androgen was not found to be a consistent characteristic of the Rodentia. Arguably, this reflects the adaptive requirements of diverse social and physical milieu.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636937 |
| Date | January 1980 |
| Creators | Evans, C. M. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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