Longitudinal Multimodal Monitoring of Eight Captive Beluga Whale (Delphinapterus leucas) Pregnancies over a 25-Year...

The accurate prediction of parturition in managed beluga whales (Delphinapterus leucas) is fundamental for optimizing maternal and neonatal care; however, reliable predictive indicators remain limited. Here, eight pregnancies (five live births and three adverse pregnancy outcomes) monitored over 25 years at a single facility were retrospectively analyzed. The rectal temperatures, serum progesterone concentrations, gestation lengths, food intake, behavioral changes, and fetal heart rates of the whales were evaluated, particularly prepartum. Five successful pregnancies exhibited consistent seasonal timing and reproducible endocrine and physiological trajectories. The mean gestation length was 466 ± 8.4 days. The rectal temperatures of dams that delivered live offspring decreased by 1.6 ± 0.5 °C approximately 1.3 ± 0.5 days before parturition. In successful pregnancies, serum progesterone concentrations declined prepartum but typically remained detectable until parturition. In contrast, a concentration of approximately 1 ng/mL prior to parturition was observed in the pregnancy that resulted in stillbirth. Adverse pregnancy outcomes were associated with deviations from the patterns observed in successful pregnancies, including abnormal gestation length, notably reduced progesterone concentrations, altered fetal heart rate trajectories, and ultrasonographic evidence of fetal cranial asymmetry. These findings highlight the importance of integrated multimodal monitoring in predicting parturition and identifying abnormal pregnancy progression in managed beluga whales.