SMRU sperm whale distribution around the Balearic Islands 2003-2008

Original provider:
Enrico Pirotta, Sea Mammal Research Unit (SMRU)

Dataset credits:
Luke Rendell and Enrico Pirotta, Sea Mammal Research Unit (SMRU)

Abstract:
Sperm whale <i>Physeter macrocephalus</i> habitat preferences are still poorly understood in the Mediterranean, despite the population being classified as ‘Endangered’ by the IUCN. Techniques to make the best use of multiple data sources are important in improving this situation. This work provides
a detailed evaluation of sperm whale distribution and habitat use around the Balearic Islands using a novel analytical framework that combines transect and follow data while accounting for any autocorrelation present. During dedicated research cruises (2003 to 2008), sperm whales were
located by listening at regular intervals along a search track and subsequently followed acoustically. Sperm whales were encountered 56 times and followed for periods ranging from a few hours to 3 d. Logistic Generalized Additive Models were used to model the probability of whale presence across
the study area as a function of environmental variables, and Generalized Estimating Equations were used to account for autocorrelation. The results suggest that sperm whales do not use the region uniformly and that topography plays a key role in shaping their distribution. Moreover, solitary individuals
were found to use the habitat differently from groups. This segregation appeared to be driven by water temperature and might reflect different needs or intraspecific competition. By shedding light on sperm whale habitat preference in such a critical area, this study represents an important step
towards the implementation of conservation measures for this population.

原始提供者：
Enrico Pirotta，海洋哺乳动物研究单位（SMRU）

数据集致谢：
Luke Rendell与Enrico Pirotta，海洋哺乳动物研究单位（SMRU）

摘要：
抹香鲸（<i>Physeter macrocephalus</i>）在地中海的栖息地偏好仍知之甚少，尽管其种群已被世界自然保护联盟（IUCN）列为‘濒危’等级。充分利用多数据源的技术对于改善这一状况至关重要。本研究采用一种新颖的分析框架，结合样线数据与跟踪数据，同时考虑存在的任何自相关性，对巴利阿里群岛周边抹香鲸的分布及栖息地利用进行了详细评估。在专项研究航次（2003-2008年）期间，研究人员通过沿搜索路线定期监听定位抹香鲸，随后对其进行声学跟踪。共观测到抹香鲸56次，跟踪时长从数小时至3天不等。研究采用逻辑广义可加模型（Logistic Generalized Additive Models）来模拟研究区域内抹香鲸出现概率与环境变量之间的函数关系，并使用广义估计方程（Generalized Estimating Equations）来处理自相关性。结果表明，抹香鲸并非均匀利用该区域，地形在塑造其分布模式中发挥关键作用。此外，研究发现独居个体与群体的栖息地利用模式存在差异。这种分异现象似乎由水温驱动，或反映了不同的需求及种内竞争。通过阐明这一关键区域抹香鲸的栖息地偏好，本研究为该种群保护措施的实施迈出了重要一步。