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Longitudinal Multimodal Monitoring of Eight Captive Beluga Whale (Delphinapterus leucas) Pregnancies over a 25-Year Period
1
Port of Nagoya Public Aquarium, Nagoya Port Foundation, 1-3 Minato-machi, Minato-ku, Nagoya 455-0033, Japan
2
Laboratory of Food and Environmental Hygiene, Joint Department of Veterinary Medicine, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
3
Joint Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
*
Author to whom correspondence should be addressed.
Animals 2026, 16(13), 2062; https://doi.org/10.3390/ani16132062
Submission received: 2 May 2026
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Revised: 26 June 2026
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Accepted: 30 June 2026
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Published: 3 July 2026
(This article belongs to the Special Issue Advances in the Reproduction of Wild and Exotic Animals)
Simple Summary
Predicting parturition in captive whales is essential for ensuring the safety of both the dam and calf. In beluga whales (Delphinapterus leucas), signs indicative of impending parturition have been previously reported. However, methods that reliably predict parturition or detect all pregnancy complications are lacking. Here, we retrospectively evaluated eight beluga whale pregnancies monitored over 25 years at a single facility. We assessed the rectal temperature, serum progesterone concentration, food intake, behavior, and fetal heart rate. In successful pregnancies, these indicators followed consistent patterns, including stable progesterone concentrations that remained detectable until shortly before birth. By contrast, pregnancies with adverse outcomes exhibited atypical findings, including abnormal gestation lengths, reduced progesterone concentrations, abnormal fetal heart rates, and fetal cranial asymmetry. Complications appeared to be associated with changes across numerous monitored indicators rather than abnormalities in a single parameter. These results suggest that combining hormonal, physical, and ultrasonographic monitoring may facilitate the prediction of parturition and identify warning indicators early in pregnancy. This multimodal approach may support reproductive management and calf survival in beluga whales under human care.
Abstract
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.
