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Testes size, testosterone production and reproductive behaviour in a natural mammalian mating system

Preston, Brian T. and Stevenson, Ian R. and Lincoln, Gerald A. and Monfort, Steven L. and Pilkington, Jill G. and Wilson, Kenneth (2012) Testes size, testosterone production and reproductive behaviour in a natural mammalian mating system. Journal of Animal Ecology, 81 (1). pp. 296-305. ISSN 0021-8790

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    Abstract

    1. Testosterone (T) is a key mediator in the expression of numerous morphological and behavioural traits in mammals, but the factors underlying individual variation in circulating T levels are poorly understood. 2. The intimate structural integration of sperm and T production within the testes, alongside the dependency of sperm production on high levels of T, suggests that T requirements for spermatogenesis could be an important driver of individual differences in T. 3. To test this hypothesis, we examine how male capacity for sperm production ( as indicated by their testes size) is associated with T levels in a feral population of Soay sheep, resident on St. Kilda, Scotland, during their rutting season. 4. We found a strong positive relationship between an individual's testes size ( as measured before their seasonal enlargement) and the levels of circulating T during their rut, suggesting that T requirements for spermatogenesis has a prominent influence on the production of this androgen. 5. In contrast, body condition and competitive ability did not independently predict T levels, findings that are inconsistent with conventional 'condition-dependent' and 'challenge' hypotheses of T production. 6. This influence of male's capacity for sperm production on T appeared to be substantial enough to be biologically relevant, as testes size also predicted male aggression and mate-seeking behaviour. 7. Our results suggest that a male's inherent capacity for sperm and T production is tightly phenotypically integrated, with potential consequences for a wide range of other T-mediated reproductive traits.

    Item Type: Article
    Journal or Publication Title: Journal of Animal Ecology
    Uncontrolled Keywords: aggression ; challenge hypothesis ; condition dependence ; sexual behaviour ; Soay sheep ; sperm competition ; SPERM COMPETITION ; MATE CHOICE ; DOMESTICATED BREEDS ; COPULATORY-BEHAVIOR ; TESTICULAR ACTIVITY ; SEASONAL CYCLES ; SEXUAL-BEHAVIOR ; SOAY SHEEP ; ANDROGEN ; RAMS
    Subjects: UNSPECIFIED
    Departments: Faculty of Science and Technology > Lancaster Environment Centre
    ID Code: 53497
    Deposited By: ep_importer_pure
    Deposited On: 13 Apr 2012 12:45
    Refereed?: Yes
    Published?: Published
    Last Modified: 09 Apr 2014 23:17
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/53497

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