Abstract
Androgens are important mediators of male-male competition in many primate species. Male gorillas' morphology is consistent with a reproductive strategy that relies heavily on androgen-dependent traits (e.g., extreme size and muscle mass). Despite possessing characteristics typical of species with an exclusively single-male group structure, multimale groups with strong dominance hierarchies are common in mountain gorillas. Theory predicts that androgens should mediate their dominance hierarchies, and potentially vary with the type of group males live in. We validated the use of a testosterone enzyme immunoassay (T-EIA R156/7, CJ Munro, UC-Davis) for use with mountain gorilla fecal material by (1) examining individual-level androgen responses to competitive events, and (2) isolating assay-specific hormone metabolites via high-performance liquid chromatography. Males had large (2.6- and 6.5-fold), temporary increases in fecal androgen metabolite (FAM) after competitive events, and most captured metabolites were testosterone or 5α-dihydrotestosterone-like androgens. We then examined the relationship between males' dominance ranks, group type, and FAM concentrations. Males in single-male groups had higher FAM concentrations than males in multimale groups, and a small pool of samples from solitary males suggested they may have lower FAM than group-living peers. However, data from two different time periods (n = 1610 samples) indicated there was no clear relationship between rank and FAM concentrations, confirming results from the larger of two prior studies that measured urinary androgens. These findings highlight the need for additional research to clarify the surprising lack of a dominance hierarchy/androgen relationship in mountain gorillas.
| Original language | English (US) |
|---|---|
| Article number | e23295 |
| Journal | American journal of primatology |
| Volume | 83 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 2021 |
Funding
The authors are grateful to Katie Edwards, Nicole Boisseau, and Janine Brown at the Smithsonian Conservation Biology Institute's Endocrinology Research Laboratory for their expertise and assistance with HPLC analyses, as well as to Diane Armstrong, Michael Landeche, and Katie Fowler for their laboratory work. We thank the Rwandan government and the Rwanda Development Board for their long-term support of the research, monitoring, and protection activities of The Dian Fossey Gorilla Fund's Karisoke Research Center. We are indebted to all Karisoke field staff for their tireless support in collecting fecal samples and long-term behavioral data. This study was supported by the Lincoln Park Zoo's Davee Center for Epidemiology and Endocrinology; Northwestern University; the Wenner-Gren Foundation (Grant No.: 20110146); the National Science Foundation (Doctoral Dissertation Improvement Grant No.: 1122321, award numbers 1405101 and 1552185, and the Graduate Research Fellowship Program); the Leakey Foundation; Sharon and Herb Lurie; and the donors who support The Dian Fossey Gorilla Fund. The authors are grateful to Katie Edwards, Nicole Boisseau, and Janine Brown at the Smithsonian Conservation Biology Institute's Endocrinology Research Laboratory for their expertise and assistance with HPLC analyses, as well as to Diane Armstrong, Michael Landeche, and Katie Fowler for their laboratory work. We thank the Rwandan government and the Rwanda Development Board for their long‐term support of the research, monitoring, and protection activities of The Dian Fossey Gorilla Fund's Karisoke Research Center. We are indebted to all Karisoke field staff for their tireless support in collecting fecal samples and long‐term behavioral data. This study was supported by the Lincoln Park Zoo's Davee Center for Epidemiology and Endocrinology; Northwestern University; the Wenner‐Gren Foundation (Grant No.: 20110146); the National Science Foundation (Doctoral Dissertation Improvement Grant No.: 1122321, award numbers 1405101 and 1552185, and the Graduate Research Fellowship Program); the Leakey Foundation; Sharon and Herb Lurie; and the donors who support The Dian Fossey Gorilla Fund.
Keywords
- aggression
- behavior
- great ape
- hormones
- male-male competition
- mating
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
