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Testosterone is positively related to the output of nematode eggs in male alpine ibex (Capra ibex) faeces


Decristophoris, P M A; von Hardenberg, A; McElligott, A G (2007). Testosterone is positively related to the output of nematode eggs in male alpine ibex (Capra ibex) faeces. Evolutionary Ecology Research, 9:1277-1292.

Abstract

Question: Does testosterone suppress the immune system of males in a strongly sexually dimorphic and long-lived ungulate?

Immunocompetence handicap hypothesis: Testosterone promotes the development of secondary sexual characteristics and simultaneously suppresses immunological defence.

Organisms: Free-ranging and individually identifiable male Alpine ibex (Capra ibex).

Methods: In faecal samples, measure testosterone levels (ng · g−1) and the number of parasite eggs per gram of faeces (faecal egg counts). Determine social dominance by observing the outcomes of agonistic interactions in the field. Weigh males at a salt-lick scale.

Data analysis: Path analysis to examine the relationships between testosterone levels, dominance, body mass, age, and faecal egg counts.

Conclusions: We found a strong positive effect of testosterone on the amount of parasite eggs in the faeces of males. The level of parasite infection did not depend on any other tested variable. Testosterone therefore has an immunosuppressive effect in male Alpine ibex, as
suggested by the immunocompetence handicap hypothesis.

Question: Does testosterone suppress the immune system of males in a strongly sexually dimorphic and long-lived ungulate?

Immunocompetence handicap hypothesis: Testosterone promotes the development of secondary sexual characteristics and simultaneously suppresses immunological defence.

Organisms: Free-ranging and individually identifiable male Alpine ibex (Capra ibex).

Methods: In faecal samples, measure testosterone levels (ng · g−1) and the number of parasite eggs per gram of faeces (faecal egg counts). Determine social dominance by observing the outcomes of agonistic interactions in the field. Weigh males at a salt-lick scale.

Data analysis: Path analysis to examine the relationships between testosterone levels, dominance, body mass, age, and faecal egg counts.

Conclusions: We found a strong positive effect of testosterone on the amount of parasite eggs in the faeces of males. The level of parasite infection did not depend on any other tested variable. Testosterone therefore has an immunosuppressive effect in male Alpine ibex, as
suggested by the immunocompetence handicap hypothesis.

Citations

20 citations in Web of Science®
24 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Zoology (former)
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:body mass, dominance, faecal egg counts, immunocompetence, immunosuppression, path model
Language:English
Date:2007
Deposited On:11 Feb 2008 12:17
Last Modified:05 Apr 2016 12:15
Publisher:Evolutionary Ecology Ltd
ISSN:1522-0613
Related URLs:http://www.evolutionary-ecology.com/issues/v09n08/ffar2169.pdf
Permanent URL: http://doi.org/10.5167/uzh-714

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