Developing low-cost tags: assessing the ecological impacts of tethered tag technology on host species

Abstract

Understanding and mitigating potential effects of tags on instrumented animals is a crucial consideration when developing new tracking techniques. Some populations of aquatic megafauna spend the majority of their lives occupying small home ranges, yet conventional finescale tracking methods generally provide a limited number of non-continuous locations, while new technology is cost prohibitive. We developed a low-cost tethered telemetry system (<185 USD tag −1 ) for short-term tracking of marine turtles in nearshore environments that incorporated standard GPS data loggers and VHF transmitters into buoyant tags of 3 different designs. We then estimated the drag of each tethered tag using an instrumented flow tunnel, deployed them on freeliving green turtles along Mexico's Baja California peninsula, and compared movement patterns of turtles equipped with high-and low-drag tags. All tags provided high-resolution tracks that ranged from 5.2 to 184.0 h (mean ± SD = 43.2 ± 37.8 h; n = 26 turtles) for a total of 1122 h. We found that the first 2 tag designs increased drag on large juveniles at typical swimming speeds by approximately 7 to 10%, which is comparable to predicted drag increases incurred by similarly sized green turtles from most commercially available electronic tags. By contrast, the third tag design increased drag by 1% or less. Turtles fitted with the high-drag tags made fewer course changes and exhibited straighter (less tortuous) movements than those fitted with the low-drag tags. Although it is unclear if the observed behavioral differences were due entirely to the tags, our results highlight the importance of evaluating potential ecological impacts of telemetry devices on host species, particularly when developing new technology.

Asset Tracking Whales—First Deployment of a Custom-Made GPS/GSM Suction Cup Tag on Migrating Humpback Whales

“…The tags are therefore limited to developed coastlines and certain species for short term deployments. If an animal or released tag comes within GSM range, data can be relayed provided sufficient battery power [34]. The technology has not been used on whales to our knowledge due to their short surface intervals (surface series for breathing between consecutive dives), which limit real time tracking and can result in the loss of tags in remote locations.…”

Quantifying local ecological knowledge to model historical abundance of long-lived, heavily-exploited fauna

“…Foraging habitats include pre-reproductive life stages—which are the most abundant life stages in the population—along with adults of both sexes. Furthermore, foraging habitats are where green turtles spend the majority of their life: juveniles may spend 20 years or more in foraging grounds until reaching maturity, and adults reside at feeding grounds during non-breeding periods ( Seminoff, Resendiz & Nichols, 2002 ; Seminoff & Shanker, 2008 ; Senko et al, 2019 ). Thus, expanding data on foraging habitats is of utmost importance for a holistic understanding of population status ( Chaloupka et al, 2008 ; Mazaris et al, 2017 ; Wildermann et al, 2018 ).…”

Movements of loggerhead sea turtles (Caretta caretta) in the Gulf of California: integrating satellite telemetry and remotely sensed environmental variables

“…Although turtles D and A had the highest MSI value (0.75 and 0.56, respectively) and exhibited the greatest travel rates (mean = 18.87 and 19.18 km days −1 respectively), they presented different migration strategies. While Turtle A remained within the release location, and then initiated a migration towards the Central North Pacific (CNP), Turtle D departed shortly after deployment further inside the GC and exhibited a high travel rate (18.87 km day −1 ) until it reached Tiburon Island where it presented the lowest travel rate of this study (1.39 km day −1 ) and remained for ~60 days, ceasing its search behaviour (Zollner & Lima, 1999; Senko et al ., 2019). Turtles B, C and E showed low MSI values (range = 0.15–0.44), indicating that they made more sinuous movements, which according to optimal search strategy (Zollner & Lima, 1999), indicates that these turtles performed search behaviour in greater measure until their arrival to the identified foraging sites.…”

“…It is among the largest for loggerheads at foraging sites in the Mexican Pacific (Ramírez-Cruz et al ., 1991; Resendiz et al ., 1998; Nichols 2002; Seminoff et al ., 2004; Peckham et al ., 2011). Due to this, and the minimum drag associated with the tags we used in this study (calculated by Jones et al ., 2014 for the tags used for olive ridley ( Lepidochelys olivacea ) and green ( Chelonia mydas ) turtles), we infer that drag caused by satellite transmitter placement was not a determinant for loggerhead movements presented here, as other studies have reported (Senko et al ., 2019).…”