Blue and fin whales Southern California 2014-2015 - Argos data

Background: Argos satellite telemetry is used globally to track terrestrial and aquatic megafauna, yet the accuracy of this system has been described empirically only for a limited number of species. We used Argos-linked archival tags with Fastloc GPS deployed on free-ranging sperm (Physeter macrocephalus), blue (Balaenoptera musculus), and fin (B. physalus) whales to derive empirical estimates of Argos location errors for these species, examine possible behavior-related differences, and test the effect of incorporating species-specific error parameters on performance of a commonly used movement model. Results: Argos location errors for blue and fin whale tags were similar and were combined (n = 1712 locations) for comparison against sperm whale tags (n = 1206 locations). Location error magnitudes for tags attached to sperm whales were significantly larger than blue/fin whale tags for almost all Argos location classes (LC), ranging from 964 m versus 647 m for LC 3, respectively, to 10,569 m versus 5589 m for LC B, respectively. However, these differences were not seen while tags floated at the surface after release. Sperm whale tags were significantly colder than ambient temperature when surfacing from a dive, compared to blue/fin whale tags (16.9 °C versus 1.3 °C, respectively) leading to larger changes in tag temperature during post-dive intervals. The increased rate of tag temperature change while at the surface was correlated to increased error magnitude for sperm whales but not blue/fin whales. Movement model performance was not significantly improved by incorporating species-specific error parameters. Conclusions: Location accuracy estimates for blue/fin whales were within the range estimated for other marine megafauna, but were higher for sperm whales. Thermal inertia from deep, long-duration dives likely caused transmission frequency drift and greater Argos location error in sperm whales, as tags warmed at the surface during post-dive intervals. Thus, tracks of deep-diving species may be less accurate than for other species. However, differences in calculated error magnitude between species were less than typical scales of movement and had limited effect on movement model performance. Therefore, broad-scale interpretation of Argos tracking data will likely be unaffected, although fine-scale interpretation should be made with more caution for deep-diving species inhabiting warm regions.

研究背景：Argos卫星遥测技术（Argos satellite telemetry）目前在全球范围内被用于追踪陆生与水生大型动物，但该系统的定位精度仅在有限的物种中得到过实证验证。本研究通过部署在自由活动的抹香鲸（Physeter macrocephalus）、蓝鲸（Balaenoptera musculus）与长须鲸（B. physalus）身上的搭载Fastloc GPS的Argos关联存档标签，针对这些物种推导了Argos定位误差的经验估算值，分析了可能与行为相关的误差差异，并检验了纳入物种特异性误差参数对常用运动模型性能的影响。

研究结果：蓝鲸与长须鲸标签的Argos定位误差水平相近，因此将二者的数据合并（共1712个定位点），与抹香鲸标签的数据（共1206个定位点）进行对比。在几乎所有Argos定位等级（LC）下，抹香鲸标签的定位误差幅值均显著高于蓝鲸/长须鲸标签：LC 3等级下二者误差分别为964米与647米，LC B等级下则分别为10569米与5589米。但在标签释放后漂浮于海面的阶段，未观察到上述差异。与蓝鲸/长须鲸标签相比，抹香鲸标签在潜水上浮时的温度显著低于环境温度（分别为16.9℃与1.3℃），导致潜航后间隔期内标签温度的变化幅度更大。海面阶段标签温度的升高速率与抹香鲸的定位误差幅值呈显著正相关，但在蓝鲸/长须鲸中未发现该关联。纳入物种特异性误差参数并未显著提升运动模型的性能。

研究结论：蓝鲸与长须鲸的定位精度估算值处于其他海洋大型动物的精度区间内，但抹香鲸的定位精度更低。深潜、长时潜水带来的热惯性可能导致了抹香鲸的传输频率漂移与更大的Argos定位误差——因为潜航后标签在海面会逐渐升温。因此，深潜物种的追踪轨迹精度可能低于其他物种。不过，物种间的误差幅值差异小于典型的运动尺度，对运动模型性能的影响有限。因此，尽管对于栖息在温暖海域的深潜物种，小尺度的轨迹解读需更为谨慎，但Argos追踪数据的大尺度解读大概率不会受到影响。