@article{4d84f7e0953543eca610a77f864ba6a5,
title = "Lean muscle mass, not aggression, mediates a link between dominance rank and testosterone in wild male chimpanzees",
abstract = "Testosterone promotes mating effort, which involves intraspecific aggression for males of many species. Therefore, males with higher testosterone levels are often thought to be more aggressive. For mammals living in multimale groups, aggression is hypothesized to link male social status (i.e. dominance rank) and testosterone levels, given that high status predicts mating success and is acquired partly through aggressive intragroup competition. In male chimpanzees, Pan troglodytes, dominance rank has been repeatedly linked to interindividual variation in testosterone levels, but evidence directly linking interindividual variation in testosterone and aggression is lacking. In the present study, we test both aggression levels and lean muscle mass, as measured by urinary creatinine, as links between dominance rank and testosterone levels in a large sample of wild male chimpanzees. Multivariate analyses indicated that dominance rank was positively associated with total rates of intragroup aggression, average urinary testosterone levels and average urinary creatinine levels. Testosterone was positively associated with creatinine levels but negatively associated with total aggression rates. Furthermore, mediation analyses showed that testosterone levels facilitated an association between dominance rank and creatinine levels. Our results indicate that (1) adult male chimpanzees with higher average testosterone levels are often higher ranking but not more aggressive than males with lower testosterone and (2) lean muscle mass links dominance rank and testosterone levels in Ngogo males. We assert that aggression rates are insufficient to explain links between dominance rank and testosterone levels in male chimpanzees and that other social variables (e.g. male–male relationship quality) may regulate testosterone's links to aggression.",
keywords = "aggression, challenge hypothesis, chimpanzee, competition, creatinine, mating effort, muscle mass, primate, social status, testosterone",
author = "Negrey, {Jacob D.} and Tobias Deschner and Langergraber, {Kevin E.}",
note = "Funding Information: We thank the Uganda Wildlife Authority and Uganda National Council for Science and Technology for permission to work in Kibale National Park. For field and lab assistance, we thank Chris Aliganyira, Samuel Angedakin, Natasha Bartolotta, Verena Behringer, Charles Birungi, Charles Businge, Jeremy Clift, Rebecca Davenport, Sarah Dunphy-Lelii, Melissa Emery Thompson, Janette Gleiche, Emily Gregg, Claudia Herf-Collet, Brian Kamugyisha, Christina Kompo, Natalie Laudicina, Godfrey Mbabazi, John Mitani, Roger Mundry, R{\'o}is{\'i}n Murtagh, Lawrence Ndangizi, Rachna Reddy, Carolyn Rowney, Joshua Rukundo, Aaron Sandel, Vera Schmeling, James Tibisimwa, Alfred Tumusiime, Ambrose Twineomujuni and David Watts. We also thank Cheryl Knott, Rachna Reddy and Ben Trumble for helpful conversations and comments on the manuscript. This work was supported by the Boston University Graduate School of Arts and Sciences , Nacey Maggioncalda Foundation , National Geographic Society ( 9824-15 ), U.S. National Institutes of Health ( 5R01AG049395 ), U.S. National Science Foundation ( BCS-1613393 ) and Wenner-Gren Foundation . Funding Information: We thank the Uganda Wildlife Authority and Uganda National Council for Science and Technology for permission to work in Kibale National Park. For field and lab assistance, we thank Chris Aliganyira, Samuel Angedakin, Natasha Bartolotta, Verena Behringer, Charles Birungi, Charles Businge, Jeremy Clift, Rebecca Davenport, Sarah Dunphy-Lelii, Melissa Emery Thompson, Janette Gleiche, Emily Gregg, Claudia Herf-Collet, Brian Kamugyisha, Christina Kompo, Natalie Laudicina, Godfrey Mbabazi, John Mitani, Roger Mundry, R{\'o}is{\'i}n Murtagh, Lawrence Ndangizi, Rachna Reddy, Carolyn Rowney, Joshua Rukundo, Aaron Sandel, Vera Schmeling, James Tibisimwa, Alfred Tumusiime, Ambrose Twineomujuni and David Watts. We also thank Cheryl Knott, Rachna Reddy and Ben Trumble for helpful conversations and comments on the manuscript. This work was supported by the Boston University Graduate School of Arts and Sciences, Nacey Maggioncalda Foundation, National Geographic Society (9824-15), U.S. National Institutes of Health (5R01AG049395), U.S. National Science Foundation (BCS-1613393) and Wenner-Gren Foundation. Publisher Copyright: {\textcopyright} 2023",
year = "2023",
month = aug,
doi = "10.1016/j.anbehav.2023.06.004",
language = "English (US)",
volume = "202",
pages = "99--109",
journal = "Animal Behaviour",
issn = "0003-3472",
publisher = "Academic Press Inc.",
}