title: Testosterone and tusks: maturation and seasonal reproductive patterns of live, free-ranging male dugongs (Dugong dugon) in a subtropical population.
abstract: Knowledge of male reproductive status and activity in free-ranging animals is vital to understanding reproductive patterns and population dynamics. Until now, almost all information regarding reproductive behavior of the dugong, a cryptic marine mammal, has relied on post-mortem examination. We examined the relationships between body length, tusk eruption (secondary sexual characteristic), seasonality, and group association on fecal testosterone metabolite concentrations in 322 free-ranging dugongs (159 males, 163 females) in subtropical Moreton Bay, Australia. Fecal testosterone concentrations demonstrated biologically meaningful differences in testicular activity between sexes and across reproductive/age classes, and were correlated with circulating concentrations in serum. Male dugongs have a pre-reproductive period that persists until a body length of 240 cm is achieved. Puberty apparently occurs between 240 and 260 cm body length when fecal testosterone levels increase fourfold (>500 ng/g) over juvenile levels, and is associated with tusk eruption. However, social maturity may be delayed until male dugongs are larger than 260 cm with well-developed tusks. In mature males, the lowest (<500 ng/g) fecal testosterone concentrations occur in the austral autumn months with maximal concentrations in September-October, coincident with the onset of a spring mating season. During spring, solitary mature males had fecal testosterone concentrations double those of mature males sampled within groups, potentially suggesting a mating strategy involving roving of reproductively active males. This study demonstrates that single-point physiological data from individuals across a population have value as indicators of reproductive processes. Our approach provides an efficacious non-lethal method for the census of reproductive status and seasonality in live male dugongs.
authors.affiliation: School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia. e.burgess1@uq.edu.au
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Burgess
authors.forename: Janet M
authors.initials: JM
authors.lastname: Lanyon
authors.forename: Tamara
authors.initials: T
authors.lastname: Keeley
mesh_terms: D000367:Age Factors; D000375:Aging / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal; D049628:Body Size; D020454:Dugong / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D008297:Male; D012098:Reproduction; D012621:Seasons; D012737:Sex Factors; D012741:Sexual Maturation; D012919:Social Behavior; D013739:Testosterone / Q000378:metabolism*; D014078:Tooth Eruption
chemical_list: D013739:Testosterone