Urinary Prolactin Concentrations in the Female Bottlenose Dolphin (Tursiops truncatus)

This long-term project provides the first look at serial prolactin concentrations in the female bottle-nose dolphin (Tursiops truncatus) during known reproductive states using non-invasive urine sampling. Prolactin concentrations were detectable during anestrus, estrous, pregnancy, lactation, and when non-mothers cohabitate with mother-calf dyads. Prolactin concentrations were higher during pregnancy than during the luteal phase of the estrous cycle indicating a possible role in pregnancy maintenance. A prolactin rise at the end of gestation suggests an involvement in pre-parturition mammary gland development, and concentrations were higher in months 1 through 5 of lactation vs months 15 through 18. Prolactin concentrations were found to be elevated in both nulliparous and parous non-mothers when they cohabitated with mother-newborn dyads, and lactational anestrous was observed. Spontaneous lactation occurred in a nulliparous female when cohabitating with a mother-newborn calf dyad that was positively correlated with elevated prolactin concentrations. There was no positive correlation between northern meteorological seasons and prolactin concentrations suggesting that dolphins may not use photoperiod in reproduction regulation as is observed in horses and sheep. Methodologies such as mammary gland ultrasound and testing urinary pro!actin in pregnant females to help predict healthy vs unhealthy pregnancies could be used by field researchers conducting wild dolphin health assessments. This information is of particular importance when investigating the long-term effects of the Deepwater Horizon oil spill on bottlenose dolphin reproduction in the Gulf of Mexico.