Skip to main content

Research Repository

Advanced Search

Changes in the secondary sexual adornments of male mandrills (Mandrillus sphinx) are associated with gain and loss of alpha status.

Setchell, J.M.; Dixson, A.F.

Authors

A.F. Dixson



Abstract

Two semifree-ranging mandrill groups, inhabiting large, naturally rainforested enclosures in Gabon, were studied to measure morphological, endocrine, and behavioral changes that occurred when adult males rose, or fell, in dominance rank. Gaining alpha rank (N = 4 males) resulted in increased testicular size and circulating testosterone, reddening of the sexual skin on the face and genitalia, and heightened secretion from the sternal cutaneous gland. Blue sexual skin coloration was unaffected. New alpha males increased in rump "fattedness," but not in body mass, and spent more time associated with other group members, rather than ranging alone. Loss of alpha position (N = 4 males) resulted in less pronounced effects than those that occurred after males had risen to alpha positions. Deposed alpha males showed decreased testicular volume, decreased body mass, a reduction in the extent of red (but not blue) sexual skin coloration, and decreased sternal gland activity. Deposed males did not decrease in the brightness of sex skin coloration. These results demonstrate that male-male competition and rank reversals have remarkable effects upon testicular function, secondary sexual traits, and behavior in the adult male mandrill. Secondary sexual traits respond to changes in male social status and therefore may be important as intrasexual signals of dominance rank.

Citation

Setchell, J., & Dixson, A. (2001). Changes in the secondary sexual adornments of male mandrills (Mandrillus sphinx) are associated with gain and loss of alpha status. Hormones and Behavior, 39, 177-184

Journal Article Type Article
Publication Date 2001
Journal Hormones and Behavior
Print ISSN 0018-506X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 39
Pages 177-184
Keywords Mandrillus sphinx; mandrill; secondary sexual adornments; testis size; testosterone; sexual selection
Public URL https://durham-repository.worktribe.com/output/1543130