Reproductive hormone profiles in captive male orangutans: Implications for understanding developmental arrest

For many years researchers have described some male orangutans as “subadult.” These males are of adolescent to adult age and are reproductive, but have little to no secondary sexual trait development. Until now the only endocrine study of this arrest of secondary sexual trait development was perform...

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Published inAmerican journal of physical anthropology Vol. 109; no. 1; pp. 19 - 32
Main Authors Maggioncalda, Anne N., Sapolsky, Robert M., Czekala, Nancy M.
Format Journal Article
LanguageEnglish
Published New York John Wiley & Sons, Inc 01.05.1999
Wiley-Liss
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Summary:For many years researchers have described some male orangutans as “subadult.” These males are of adolescent to adult age and are reproductive, but have little to no secondary sexual trait development. Until now the only endocrine study of this arrest of secondary sexual trait development was performed by Kingsley (1982, 1988). She found that “subadult” or arrested males have lower testosterone levels than similar age developing adolescents or adult males. In this study, urine samples were collected over a two‐year period from 23 captive male orangutans in order to more fully define male endocrine profiles. Three study males were juveniles, seven were arrested adolescents, six were developing adolescents, and seven were mature adults. Morning samples were analyzed by radioimmunoassay for levels of testicular steroids and gonadotropins and group hormone profiles were compared by analysis of variance. Results illustrate that arrested adolescent orangutans have significantly lower testosterone and dihydrotestosterone (DHT) levels than developing adolescents, but significantly higher levels than juveniles. Luteinizing hormone (LH) levels also differed between arrested and developing adolescents, with arrested males having lower levels. However, follicle stimulating hormone (FSH) levels were similar in both morphs of adolescent male. The overall hormone profiles for arrested and developing adolescent male orangutans suggest that arrested males lack levels of LH, testosterone, and DHT necessary for development of secondary sexual traits. However, they have sufficient testicular steroids, LH, and FSH to fully develop primary sexual function and fertility. These endocrine data help define alternative developmental pathways in male orangutans. The authors discuss the relationship between these developmental pathways and male orangutan reproductive strategies, and hypothesize about their prepubertal socioendocrine determination. Am J Phys Anthropol 109:19–32, 1999. © 1999 Wiley‐Liss, Inc.
Bibliography:istex:61495B619435DCB9DB99A9C8687ABA9AC38B7A76
Sigma Xi
The L.S.B. Leakey Foundation
ark:/67375/WNG-0GWKTGS3-V
The Harry Frank Guggenheim Foundation
The Center for Reproduction of Endangered Species
The Chicago Zoological Society
Duke University Graduate School
ArticleID:AJPA3
ObjectType-Article-2
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ISSN:0002-9483
1096-8644
DOI:10.1002/(SICI)1096-8644(199905)109:1<19::AID-AJPA3>3.0.CO;2-3