Testosterone-related and seasonal changes in sebaceous glands in the back skin of adult male brown bears (Ursus arctos)

• Main Authors: Tomiyasu, Jumpei, Yanagawa, Yojiro, Sato, Yoshikazu, Shimozuru, Michito, Nagano, Masashi, Sasaki, Motoki, Sakamoto, Hideyuki, Matsumoto, Naoya, Kobayashi, Kohei, Kayano, Mitsunori, Haneda, Shingo, Matsui, Motozumi
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2017
• Subjects: Ursus arctos
• Online Access: http://hdl.handle.net/1807/82680; http://www.nrcresearchpress.com/doi/abs/10.1139/cjz-2017-0028

Adult male brown bears (Ursus arctos; Linnaeus, 1758) display tree-marking behavior to chemically signalize the dominance throughout the non-denning period, and this behavior peaks during breeding season. Within the scent-marking sequence, back rub is one of a core marking postures. The present study investigated 1) seasonal changes in sebaceous glands in the back skin of brown bears and 2) the relationship between those changes and testosterone levels. Back skin tissue samples and blood were collected from captive adult intact and castrated males during pre-breeding, transitional, breeding and post-breeding seasons, which were concurrent with back skin observations. In intact males, during the transitional and breeding seasons, an oily secretion from the back skin was observed along with enlarged sebaceous glands. The plasma testosterone concentrations during the transitional and breeding seasons were increased compared with the pre- and post-breeding seasons. Secretions and enlarged sebaceous glands were not found in castrated males, and the plasma testosterone concentrations remained at baseline levels. Oily secretions of the back skin glands that appear more abundant during breeding season are rubbed against trees. Changes in size and volume of sebaceous glands, and thus their secreting capacity, are likely testosterone-regulated. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.