SPERMATOGENESIS ZONALITY AND AGE OF SEXUAL MATURITY IN MALE COMMON BOTTLENOSE DOLPHINS (<i>Tursiops truncatus</i>) STRANDED IN SOUTH CAROLINA, USA

Abstract

The common bottlenose dolphin (<i>Tursiops truncatus</i>) is the most frequently stranded marine mammal in the southeastern United States. Age of sexual maturity is an important life history parameter used to plan and assess management strategies for animal populations. However, little information exists regarding age and length at sexual maturity for recently-established resident stocks of <i>T. truncatus</i> along the southeastern USA compared to larger migratory groups. Additionally, previous work has not clearly addressed the presence of zonality in the testes of common bottlenose dolphins. This study used histological examination of the testes of 82 individuals stranded in South Carolina, USA whose ages were quantified using growth layer groups in decalcified teeth. The age range of youngest mature-oldest immature dolphin was 10 to 12 years, with a median age of sexual maturity of 14.3 years (95% confidence interval 12.1-15.9 years) and median length at sexual maturity of 236.6 cm (95% confidence interval 227.4-238.3 cm). Zonality was assessed by systematically examining 13 regions of the testis in 16 individuals; no zonality was found, indicating that testis sampling can be done at any region.