An at-sea assessment of Argos location accuracy for three species of large whales, and the effect of deep-diving behavior on location error

Ladd M Irvine,Tomas M Follett,Martha H Winsor,Daniel M Palacios,Bruce R Mate

doi:10.1186/s40317-020-00207-x

Ladd M Irvine, Tomas M Follett + Show 3 more

Open Access

https://doi.org/10.1186/s40317-020-00207-x

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Abstract

BackgroundArgos 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.ResultsArgos 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.ConclusionsLocation 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.

Highlights

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
A total of 8502 Argos locations and 20,852 Fastloc global positioning system (GPS) locations were generated while tags were attached to whales, and 2300 Argos locations and 1079 Fastloc GPS locations were generated after the tags had released from whales and were floating at the surface prior to recovery (Table 1)
The species-specific Argos location error characterization we have conducted for three large-whale species will better inform a wide range of future telemetry studies on cetaceans and other marine megafauna

Summary

Introduction

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. Other discoveries include unexpected reproductive connections between endangered and non-endangered populations [11] and the use of possible navigational cues during long-distance migrations [12]. These data have informed models developed to better understand the environmental drivers behind the animals’ movements and to better predict their distribution and possible responses to future environmental changes [13,14,15,16,17,18]. Bio-telemetry and bio-logging approaches have led to useful management applications such as the identification of potential anthropogenic conflicts [19, 20], the development of new mitigation tools [21,22,23], and the generation of information critical for conservation and management policy at a global scale [24, 25]

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