Fernandez Ajó A, Buck C L, Hunt K E, Pirotta E, New L, Dillon D, Bierlich K C, Hildebrand L, Bird C N, Torres L G
Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife and Conservation Sciences, Oregon State University, 2030 SE Marine Science Dr, Newport, OR 97365, USA.
Department of Biological Sciences, Northern Arizona University, 617 S. Beaver St., Flagstaff, AZ 86011, USA.
Conserv Physiol. 2025 Jan 20;13(1):coae094. doi: 10.1093/conphys/coae094. eCollection 2025.
Understanding wildlife reproductive seasonality is crucial for effective management and long-term monitoring of species. This study investigates the seasonal variability of testosterone in male Pacific Coast Feeding Group (PCFG) gray whales, using an eight-year dataset (2016-2023) of individual sightings, drone-based photogrammetry and endocrine analysis of faecal samples. We analyzed the relationship between faecal testosterone levels and total body length (TL), body condition (body area index, BAI), sexual maturity and day of the year using generalized additive mixed models. Our findings reveal a significant increase in faecal testosterone levels in mature males (MM) towards the end of the foraging season. This increase was not observed in JM, highlighting age-dependent development of sexual characteristics. No significant relationship was found between testosterone levels and TL. Additionally, BAI was not significantly associated with testosterone levels. Our results suggest that the increasing testosterone levels in MM gray whales may indicate preparation for mating before the southbound migration. These findings provide valuable insights into the reproductive biology of PCFG gray whales and underscore the importance of non-invasive faecal sampling for studying reproductive seasonality in large whales. Our approach not only provides further insights into the seasonality of male reproduction for the PCFG gray whales but also offers tools to enhance the understanding of male reproduction in baleen whales broadly with non-invasive approaches.
了解野生动物繁殖的季节性对于物种的有效管理和长期监测至关重要。本研究利用一个为期八年（2016 - 2023年）的数据集，该数据集包含个体目击记录、基于无人机的摄影测量以及粪便样本的内分泌分析，调查了太平洋海岸觅食群（PCFG）雄性灰鲸睾酮的季节性变化。我们使用广义相加混合模型分析了粪便睾酮水平与体长（TL）、身体状况（体面积指数，BAI）、性成熟度和一年中的日期之间的关系。我们的研究结果显示，成熟雄性（MM）在觅食季节接近尾声时，粪便睾酮水平显著升高。在未成年雄性（JM）中未观察到这种升高，这突出了性特征的年龄依赖性发育。未发现睾酮水平与TL之间存在显著关系。此外，BAI与睾酮水平也没有显著关联。我们的结果表明，MM灰鲸睾酮水平的升高可能表明在向南迁徙之前为交配做准备。这些发现为PCFG灰鲸的繁殖生物学提供了有价值的见解，并强调了非侵入性粪便采样在研究大型鲸鱼繁殖季节性方面的重要性。我们的方法不仅为PCFG灰鲸雄性繁殖的季节性提供了进一步的见解，还提供了工具，以通过非侵入性方法更广泛地增进对须鲸雄性繁殖的理解。
