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Why Do Male Reindeer (Rangifer T. Tarandus) Have Higher Abundance of Second and Third Instar Larvae of Hypoderma Tarandi Than Females?

Ivar Folstad, Arne C. Nilssen, Odd Halvorsen and Johan Andersen
Oikos
Vol. 55, No. 1 (May, 1989), pp. 87-92
Published by: Wiley on behalf of Nordic Society Oikos
DOI: 10.2307/3565877
Stable URL: http://www.jstor.org/stable/3565877
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Why Do Male Reindeer (Rangifer T. Tarandus) Have Higher Abundance of Second and Third Instar Larvae of Hypoderma Tarandi Than Females?
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Abstract

1305 reindeer (Rangifer t. tarandus L.) of different age and sex have been examined with regard to infections of second and third instar Hypoderma tarandi (L.) larvae. Females and castrates revealed low larval abundance compared with males and calves, and females show, in general, a decreasing larval abundance with increasing age. Intact males have, in contrast to females and castrates, a positive correlation between dressed weight and number of parasites. These results are discussed with reference to sex and age group variation in immunocompetence and avoidance behaviour to ovipositing warble-flies. It is suggested that reindeer acquire immunity to recurrent infections. Intact males are assumed to reduce the ability to elicit an effective immune response due to high plasma-free corticosteroid concentrations from the joint action of rut stress and high plasma-free testosterone concentrations. This may explain the different dynamics in males and castrates, and contain an element of stabilizing selection.

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