TY - JOUR
T1 - Group-level competition influences urinary steroid hormones among wild red–tailed monkeys, indicating energetic costs
AU - Jaeggi, Adrian V.
AU - Trumble, Benjamin C.
AU - Brown, Michelle
N1 - Funding Information:
The authors thank Catherine Crockford, Tobias Deschner, Liza Moscovice and Roman Wittig for valuable discussions, and Marina Cords and three anonymous reviewers for helpful comments that substantially improved this manuscript. We are also very grateful to Karen Bales for encouraging and insightful feedback. F. Angwela, G. Asaba, R. Busobozi, L. Daniel, P. Kabagambe, K. Mathias, and J. Mutambuze provided invaluable assistance in the field. This work was supported by an NSF Postdoctoral Fellowship (#1103444) and research funding from the Leakey Foundation and the University of California, Santa Barbara to M. B., and research funds from Emory University to A. V. J.
Funding Information:
National Science Foundation, Grant number: 1103444; Leakey Foundation
Publisher Copyright:
© 2018 Wiley Periodicals, Inc.
PY - 2018/5
Y1 - 2018/5
N2 - Various theories emphasize that intergroup competition should affect intragroup cooperation and social relationships, especially if the cost of intergroup competition outweighs that of intragroup competition. This cost of intergroup competition may be quantified by changes in physiological status, such as in the steroid hormones cortisol (C) and testosterone (T), which rise or are depressed during periods of energetic stress, respectively. Here we tested for changes in urinary C and T after intergroup encounters (IGEs) among wild red-tailed monkeys (Cercopithecus ascanius), a species that experiences frequent intergroup feeding competition, at the Ngogo station in Kibale National Park, Uganda. We assayed 108 urine samples, of which 36 were collected after IGEs, from 23 individuals in four social groups. Bayesian multilevel models controlling for various confounds revealed that IGEs increased C and decreased T relative to baseline, consistent with an energetic cost to IGEs. The C change was more apparent in samples collected early after IGEs, suggesting an anticipatory increase, whereas the T change was stronger in later samples, suggesting sustained energetic trade-offs. Hormone responses were not affected by the IGE outcome. This cost to intergroup competition, together with little evidence for intragroup competition in redtails and other guenons, establishes an interesting test case for theories emphasizing the effect of intergroup competition on intragroup cooperation.
AB - Various theories emphasize that intergroup competition should affect intragroup cooperation and social relationships, especially if the cost of intergroup competition outweighs that of intragroup competition. This cost of intergroup competition may be quantified by changes in physiological status, such as in the steroid hormones cortisol (C) and testosterone (T), which rise or are depressed during periods of energetic stress, respectively. Here we tested for changes in urinary C and T after intergroup encounters (IGEs) among wild red-tailed monkeys (Cercopithecus ascanius), a species that experiences frequent intergroup feeding competition, at the Ngogo station in Kibale National Park, Uganda. We assayed 108 urine samples, of which 36 were collected after IGEs, from 23 individuals in four social groups. Bayesian multilevel models controlling for various confounds revealed that IGEs increased C and decreased T relative to baseline, consistent with an energetic cost to IGEs. The C change was more apparent in samples collected early after IGEs, suggesting an anticipatory increase, whereas the T change was stronger in later samples, suggesting sustained energetic trade-offs. Hormone responses were not affected by the IGE outcome. This cost to intergroup competition, together with little evidence for intragroup competition in redtails and other guenons, establishes an interesting test case for theories emphasizing the effect of intergroup competition on intragroup cooperation.
KW - behavioral endocrinology
KW - between-group competition
KW - cooperation
KW - guenons
KW - parochial altruism
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U2 - 10.1002/ajp.22757
DO - 10.1002/ajp.22757
M3 - Article
AN - SCOPUS:85045095385
SN - 0275-2565
VL - 80
JO - American Journal of Primatology
JF - American Journal of Primatology
IS - 5
M1 - e22757
ER -