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Greenberg D, Snyder KP, Filazzola A, Mastromonaco GF, Schoof VAM. Hormonal correlates of male dominance rank, age, and genital colouration in vervet monkey (Chlorocebus pygerythrus). Gen Comp Endocrinol 2022; 316:113948. [PMID: 34826430 DOI: 10.1016/j.ygcen.2021.113948] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 11/02/2021] [Accepted: 11/19/2021] [Indexed: 01/04/2023]
Abstract
Primates are the most colourful members of the Mammalian clade. In vervet monkeys (Chlorocebus pygerythrus), males are characterized by their red penis and blue scrotum. Such colour signals are often used in conspecific communication, and thus could be used to convey signaller condition. We quantified scrotal and penile colour characteristics using digital photographs between May-June 2016 from males in two neighboring groups along the shores of Lake Nabugabo, Uganda. We examined the relationship between fecal hormones, male dominance rank, age (adult vs. immature), and colour. Adult males were higher ranking than immatures, but there were no rank or age differences in fecal hormone levels. Glucocorticoids and androgens were positively correlated in immature, but not adult males. All scrotal characteristics were predicted by age, with adult males having more teal (i.e., less blue, more green) and more luminant scrota. Within adult males, those with higher androgens levels had more saturated blue scrotal colouration and higher-ranking males were more luminant. Penile colouration was also associated with age and rank. High-ranking males had a more saturated red penis, and adult male penile colour was more luminant and bluer than in immature males. Our findings are consistent with previous reports that scrotal colouration advertises sexual or reproductive maturity (i.e., age), but we also find that within adult males, colour also advertises dominance rank and may be mediated by androgen levels. Penile colouration also appears to signal information about male age and dominance rank but does not appear to be mediated by hormones.
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Affiliation(s)
- D Greenberg
- Department of Biology, Faculty of Science, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - K P Snyder
- Department of Biology, Faculty of Science, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - A Filazzola
- Department of Biology, Faculty of Science, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
| | - G F Mastromonaco
- Reproductive Sciences Unit, Toronto Zoo, 361A Old Finch Avenue, Toronto, ON M1B 5K7, Canada
| | - V A M Schoof
- Department of Biology, Faculty of Science, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; Bilingual Biology Program, Department of Multidisciplinary Studies, Glendon College, York University, 2275 Bayview Avenue, Toronto, ON M4N 3M6, Canada.
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