Data from: Scale-dependent foraging ecology of a marine top predator modelled using passive acoustic data

1. Understanding which environmental factors drive foraging preferences is critical for the development of effective management measures, but resource use patterns may emerge from processes that occur at different spatial and temporal scales. Direct observations of foraging are also especially challenging in marine predators, but passive acoustic techniques provide opportunities to study the behavior of echolocating species over a range of scales. 2. We used an extensive passive acoustic dataset to investigate the distribution and temporal dynamics of foraging in bottlenose dolphins using the Moray Firth (Scotland, UK). Echolocation buzzes were identified with a mixture model of detected echolocation inter-click intervals, and used as a proxy of foraging activity. A robust modelling approach accounting for autocorrelation in the data was then used to evaluate which environmental factors were associated with the observed dynamics at two different spatial and temporal scales. 3. At a broad scale, foraging varied seasonally, and was also affected by sea-bed slope and shelf-sea fronts. At a finer scale, we identified variation in seasonal use and local interactions with tidal processes. Foraging was best predicted at a daily scale, accounting for site-specificity in the shape of the estimated relationships. 4. This study demonstrates how passive acoustic data can be used to understand foraging ecology in echolocating species, and provides a robust analytical procedure for describing spatio-temporal patterns. Associations between foraging and environmental characteristics varied according to spatial and temporal scale, highlighting the need for a multi-scale approach. Our results indicate that dolphins respond to coarser-scale temporal dynamics, but have a detailed understanding of finer-scale spatial distribution of resources.

1. 明确驱动觅食偏好的环境因子，对于制定高效的管理措施至关重要，但资源利用模式往往源于不同时空尺度下发生的过程。针对海洋捕食者的觅食直接观测本就极具挑战性，而被动声学技术（passive acoustic techniques）则为在多尺度下研究回声定位物种（echolocating species）的行为提供了可能。2. 本研究依托大规模被动声学数据集（passive acoustic dataset），对栖息于英国苏格兰马里湾（Moray Firth）的宽吻海豚的觅食分布及时空动态展开探究。研究通过基于检测到的回声定位点击间隔（inter-click intervals, ICI）的混合模型识别回声定位突击脉冲（echolocation buzzes），并将其作为觅食活动的替代指标。随后，采用考虑数据自相关（autocorrelation）的稳健建模方法，评估在两种不同时空尺度下，哪些环境因子与观测到的动态变化相关。3. 在大尺度下，觅食活动呈现季节变化，同时还受海底坡度（sea-bed slope）和陆架海锋（shelf-sea fronts）的影响；在更精细的尺度上，研究发现了季节性利用的差异，以及与潮汐过程的局部相互作用。在日尺度下可最优地预测觅食活动，此时需考虑估计关系中存在的位点特异性（site-specificity）。4. 本研究证实了被动声学数据可用于解析回声定位物种的觅食生态学，并为描述时空模式（spatio-temporal patterns）提供了一套稳健的分析流程。觅食活动与环境特征之间的关联随时空尺度而异，这凸显了采用多尺度研究方法的必要性。研究结果表明，海豚会响应大尺度的时间动态变化，但对资源的精细空间分布拥有精准的认知。