2025-09-23 ワシントン大学(UW)
A mother humpback whale and her calf make their way towards the surface in Tonga. Humpbacks belong to the rorqual whale family, the most common class of baleen whales and the subjects of a University of Washington study showing that longer mothers are more likely to have female calves than males.iStock
<関連情報>
- https://www.washington.edu/news/2025/09/23/longer-body-means-more-female-calves-for-whale-moms/
- https://royalsocietypublishing.org/doi/10.1098/rspb.2025.1437
より大きなシロナガスクジラの母親ほど雌の子孫を多く産む Longer rorqual whale mothers produce more female offspring
Zoe R. Rand,Trevor A. Branch and Sarah J. Converse
Proceedings of the Royal Society B Published:24 September 2025
DOI:https://doi.org/10.1098/rspb.2025.1437
Abstract
Multiple hypotheses have arisen that predict how mammals with the ability to adapt fetal sex ratios should invest in male versus female offspring to maximize inclusive fitness, but large wild-population datasets necessary for testing these hypotheses are challenging to collect. We used whaling data (n = 209 254 sexed fetuses from seven rorqual whale species) to test whether mothers with more resources to invest in offspring produce more male or female offspring. We first modelled fetal sex misidentification in the data and estimated that missexing occurred for fetuses under 30–120 cm across five of seven species. Using Bayesian generalized linear mixed models and a size-restricted dataset to account for misidentification, we estimated a 90% posterior probability that longer mothers have more female offspring overall, ranging from 77% for humpback whales to 99% for sei whales. Our results likely reflect both the difficulty of excluding small males from competition in aquatic environments and the exceptionally high costs of gestation and lactation in baleen whales.
