Semen collection and ejaculate characteristics in the Indo-Pacific bottlenose dolphin (Tursiops aduncus)

The testes of sexually mature dolphins produce large quantities of sperm. Sperm are expelled in copious amounts of seminal fluid through repeated ejaculations that can occur within a short period of time. There is currently a lack of detail about the methodology of sequential ejaculate collection in dolphins and how the traits of individual ejaculates affect the assessment of reproductive capacity. The objectives of this study were to obtain series of ejaculates from 3 dolphins by following a well-defined collection protocol and then to characterize individual ejaculates. Semen was collected weekly for 1 year from 3 sexually mature Tursiops aduncus. The end of a collection session was marked by a lack of semen, in spite of effort, or micturition. Individual ejaculates were analyzed for volume, pH, and sperm concentration, count, motility, and viability following methods previously described for dolphin semen. The first ejaculate was typically higher in volume and sperm count but lower in sperm concentration, motility, and viability. The concentration of the second ejaculate was generally the highest. Sperm motility and viability of the second and subsequent ejaculates in a series were good (ie, >80%). Collection of the first ejaculate only can lead to underestimation of reproductive capacity. Sperm output fluctuated erratically from week to week, so it was difficult to assess any seasonal pattern. Results provide information for further investigation of male dolphin reproductive patterns and any effect of collection frequency on ejaculate characteristics.