Shuttleworth, LoraineGanswindt, AndreHunt, Kathleen E.Fernandez Ajo, AlejandroPieterse, EstefanSeakamela, S. MduduziSchoeman, ChantelVermeulen, Els2025-11-272025-11-272025-06Shuttleworth, L., Ganswindt, A., Hunt, K.E. et al. 2025, 'Multiyear Baleen endocrine profiles suggest a longer estimated gestation in southern right whales (Eubalaena australis)', Ecology and Evolution, vol. 15, no. 6, art. e71528, pp. 1-13, doi : 10.1002/ece3.71528.2045-7758 (online)10.1002/ece3.71528http://hdl.handle.net/2263/106962DATA AVAILABILITY STATEMENT : The data supporting the findings of this study are available within the article and its Supporting Information. Any other data can be made available upon reasonable request to the corresponding author.Gestation length is a key reproductive parameter influencing fecundity, population growth rates, and the recovery potential of baleen whales. However, direct knowledge of the gestation length in these large mammals remains limited, primarily inferred from whaling and observational data. Over the past decade, southern right whales have experienced a decline in reproductive success, likely linked to climate-change-induced shifts in foraging conditions. Understanding the population-level consequences of these changes requires detailed longitudinal reproductive data. This study analyzes multiyear steroid hormone profiles in the baleen of adult female southern right whales stranded along the South African coast. Results show an extended hormonal pattern characterized by two peaks in progestogens between 20 and 25 months—suggesting putative pregnancies lasting substantially longer than previous estimates. Sharp estrogen peaks during periods of elevated progestogen phases may indicate hormonal regulation of myometrial contractions at birth. A positive correlation between progestogens and glucocorticoids suggests a role for glucocorticoids in pregnancy maintenance, while androgens provide limited insight into female reproduction in this species. These findings imply a longer-than-expected gestation period for southern right whales and potentially across the balaenid family. This has important implications for understanding the timing and location of conception, relevant for conservation management strategies. Multipopulation studies alongside individual sighting histories are recommended to refine our understanding of southern right whale reproduction further.en© 2025 The Author(s). Ecology and Evolution published by British Ecological Society and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License.Southern right whale (Eubalaena australis)Southern right whale (SRW)Gestation lengthBaleen whalesReproductionArticle