Authors: Katharina Foerster Bart Kempenaers
Publish Date: 2004/06/22
Volume: 56, Issue: 5, Pages: 482-490
Abstract
In temperate passerines increased testosterone T levels during breeding mediate male aggressive and mating behaviour If individual variability in T levels is reflected in behavioural differences during mating males with higher T might gain higher reproductive success This can be tested experimentally by elevating T levels However high exogenous T levels are known to have negative effects on male sperm production This may reduce male fitness particularly if sperm competition is intense We experimentally elevated T levels in breeding blue tit males to investigate how T levels above the natural mean influence male reproductive success Contrary to most—if not all—previous experimental manipulations of T levels in birds we restricted the treatment with exogenous T to the time when females were fertile and T levels were naturally high in males In blue tits extrapair paternity is an important component of male reproductive success and its frequency is likely influenced by androgenmediated behaviours such as mate attraction and aggression towards other males Here we show that Tmales were equally likely to become cuckolded and did not gain more extrapair paternity than control males Cuckolded Tmales however lost more paternity than control males We discuss the possibility that this is caused by negative effects of T treatment on sperm productionWe thank Anne Peters and three anonymous referees for comments that substantially improved the manuscript We are grateful to Kate Lessells for providing the GLIMmacro to perform the sexratio randomization tests to Cheryl Bishop Hansjörg Kunc Katharina Peer Angelika Pösel and Agnes Türk for help in the field and to Kim Carter and Sabrina Gaba for assistance with the molecular analyses RaphaelThomas Klumpp and Alfred Fojt from the Institute of Silviculture Vienna provided access to their facilities in the study area Hans Winkler from the Konrad Lorenz Institute for Comparative Ethology Vienna generously supported us during all stages of this study All applied procedures were approved by the Magistrate of Conservation in Vienna permit MA227332/97 and the Austrian Ministry of Science and Transport permit GZ 66015/10Pr/4/99
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