TY - JOUR
T1 - Separating behavioral and physiological mechanisms in testosterone-mediated trade-offs
AU - Mougeot, François
AU - Redpath, Stephen M.
AU - Piertney, Stuart B.
AU - Hudson, Peter J.
PY - 2005/8
Y1 - 2005/8
N2 - Testosterone often mediates trade-offs between reproduction and other life-history traits, which are usually investigated using testosterone implants. However, this approach does not distinguish between the physiological and behavioral effects of testosterone. We studied a wild game bird, the red grouse Lagopus lagopus scoticus, and took a new approach to investigate mechanisms linking elevated testosterone to increased parasite intensity. We caught males in autumn, removed their parasites, implanted them with the antiandrogen flutamide in combination with an aromatase inhibitor (FA males) or with empty implants (control males), and challenged them with parasites. The FA treatment increased testosterone concentration and physiological stress, but without enhancing testosterone-dependent behaviors, because testosterone receptors were blocked. FA males ended up with more parasites than the control males the following autumn, an effect similar to that of a testosterone treatment reported elsewhere. However, and unlike the testosterone treatment, the FA treatment did not affect home range, pairing, or breeding success. The results supported a physiological mechanism (increased susceptibility) linking elevated testosterone and increased parasite intensity. The FA treatment provided a new way of investigating testosterone-mediated trade-offs whereby testosterone concentration was increased while the effects on behavior were blocked, resulting in physiological costs without phenotypic benefits.
AB - Testosterone often mediates trade-offs between reproduction and other life-history traits, which are usually investigated using testosterone implants. However, this approach does not distinguish between the physiological and behavioral effects of testosterone. We studied a wild game bird, the red grouse Lagopus lagopus scoticus, and took a new approach to investigate mechanisms linking elevated testosterone to increased parasite intensity. We caught males in autumn, removed their parasites, implanted them with the antiandrogen flutamide in combination with an aromatase inhibitor (FA males) or with empty implants (control males), and challenged them with parasites. The FA treatment increased testosterone concentration and physiological stress, but without enhancing testosterone-dependent behaviors, because testosterone receptors were blocked. FA males ended up with more parasites than the control males the following autumn, an effect similar to that of a testosterone treatment reported elsewhere. However, and unlike the testosterone treatment, the FA treatment did not affect home range, pairing, or breeding success. The results supported a physiological mechanism (increased susceptibility) linking elevated testosterone and increased parasite intensity. The FA treatment provided a new way of investigating testosterone-mediated trade-offs whereby testosterone concentration was increased while the effects on behavior were blocked, resulting in physiological costs without phenotypic benefits.
UR - http://www.scopus.com/inward/record.url?scp=23044482645&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=23044482645&partnerID=8YFLogxK
U2 - 10.1086/431256
DO - 10.1086/431256
M3 - Article
C2 - 16032571
AN - SCOPUS:23044482645
SN - 0003-0147
VL - 166
SP - 158
EP - 168
JO - American Naturalist
JF - American Naturalist
IS - 2
ER -