Trade-offs between immunity and testosterone in male African ground squirrels.

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dc.contributor.authorO'Brien, Kelsey
dc.contributor.authorWaterman, Jane
dc.contributor.authorAnderson, W. Gary
dc.contributor.authorBennett, Nigel
dc.date.accessioned2020-07-03T14:03:49Z
dc.date.available2020-07-03T14:03:49Z
dc.date.issued2018-08-23
dc.date.submitted2020-07-03T00:51:27Zen_US
dc.description.abstractThe immunocompetence handicap hypothesis (ICHH) proposes that testosterone has both beneficial effects on male reproductive potential and negative effects by suppressing the immune system. However, support for the ICHH has been variable and an alternative hypothesis suggests that testosterone may be acting indirectly via cortisol to suppress immunity (the stress-linked ICHH). A third hypothesis is that increased energetic investment in immunity results in the suppression of testosterone. We tested these hypotheses in male Cape ground squirrels (Xerus inauris) through two separate manipulations: first, by triggering a strong immune response using a lipopolysaccharide (LPS) injection and, secondly, by increasing circulating testosterone using silastic testosterone implants. Responding to an immune challenge significantly reduced testosterone, supporting the immune suppression hypothesis, while increasing circulating testosterone had no effect on immunocompetence, body mass, ectoparasite abundances or cortisol levels, failing to support either the ICHH or stress-linked ICHH. Our results add to the increasing body of literature that challenges the ICHH, and we conclude that the trade-off between testosterone and immunity is mediated through immune activation and not through testosterone in male Cape ground squirrels. Being able to test the ICHH, stress-linked ICHH and immune suppression hypotheses in a free-ranging mammal gives us a unique opportunity to examine the mechanisms mediating this trade-off.en_US
dc.description.sponsorshipNatural Sciences and Engineering Research Council of Canada Canada Foundation of Innovation University of Manitoba Faculty of Science FieldWork Support grant South African Research Chairs Initiative (SARChI chair; #64756) from the Department of Science andTechnology National Research Foundation South Africa University of Manitoba (Barrett-Hamilton Award University of Manitoba Faculty of Scienceen_US
dc.identifier.citationO’Brien, KA, Waterman JM, Anderson WG, Bennett NC. 2018. Trade-offs between immunity and testosterone in male African ground squirrels. Journal of Experimental Biology. 221en_US
dc.identifier.doi10.1242/jeb.177683
dc.identifier.urihttp://hdl.handle.net/1993/34756
dc.language.isoengen_US
dc.publisherThe Company of Biologistsen_US
dc.rightsopen accessen_US
dc.subjectimmunocompetence handicap hypothesisen_US
dc.subjectcortisolen_US
dc.subjectLPSen_US
dc.subjectlipopolysaccharideen_US
dc.subjectStress-linked ICHHen_US
dc.subjectCape ground squirrelsen_US
dc.subjectXerus inaurisen_US
dc.titleTrade-offs between immunity and testosterone in male African ground squirrels.en_US
dc.typeArticleen_US
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