Reproductive success of male Atlantic spotted dolphins (Stenella frontalis) revealed by noninvasive genetic analysis of paternity

Cetaceans are known to frequently engage in sexual behavior; however, the lack of male parental investment in offspring makes assessment of male reproductive success difficult. We assessed paternity in a small population (mean individuals sighted per year = 93) of Atlantic spotted dolphins (Stenella frontalis (G. Cuvier, 1829)) utilizing noninvasively collected fecal material. Samples (n = 88) were collected from dolphins from four social clusters. Of the 29 offspring tested, 34.5% were assigned paternity, resulting in 10 paternities assigned to seven males. Our study indicates that achieving a certain age is a potential precursor for males to mate successfully, as 18 years was the youngest estimated age of a male at the time of calf conception. In all pairings but one, the males were older than the female (mean age difference = 7.7+ years). Successful males were from two of the four social clusters and males most often mated within their social group or with females from the next geographically closest group. The study combines genetic data with known maternal pedigree information and reveals patterns in the overall mating system in a cetacean species where reproductive success of males was previously unknown.