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Testosterone, sexual ornamentation and immune function in the Black-headed Gull Larus ridibundus

Korsten, P. (1998) Testosterone, sexual ornamentation and immune function in the Black-headed Gull Larus ridibundus. Master's Thesis / Essay, Biology.

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Yet there are just a few experimental studies addressing the immunocompetence handicap hypothesis of Foistad and Karter (1992). We implanted juvenile black-headed gulls Larus ridibundus with testosterone releasing tubes to experimentally test this hypothesis. The effect of testosterone on immune function, secondary sexual traits and body mass were examined. To determine immune function both the primary and the secondary antibody response after immunisation with sheep red blood cells were measured. Also the volume percentage of white blood cells, the sedimentation rate and the number of foot infections were measured. Secondary sexual traits we quantified were the brown mask, the colour of the legs and the bill and the behavioural displays that the gulls performed. As predicted by the immunocompetence handicap hypothesis, testosterone had a positive effect on mask development, bill colour brightness and display rate. However contrary to the hypothesis' predictions neither primary, nor secondary antibody response, nor any other measure of immunocompetence was affected by the testosterone treatment. Testosterone did not affect body mass either. We suggest that the testosterone treated gulls might have compensated for their greater display rates and sexual ornament sizes by having a higher food intake. We also investigated the relation between immunocompetence and secondary sexual traits and between mate choice, and immunocompetence and secondary sexual traits. We found no consistent association between immune function and secondary sexual traits. Our results on mate choice were not conclusive due to low sample size. We conclude that our results do not support the immunocompetence handicap hypothesis.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:31
Last Modified: 15 Feb 2018 07:31

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