Nowacek, D. P. | Search bioRxiv

bioRxiv2022

Trade-offs in telemetry tag programming for deep-diving cetaceans: data longevity, resolution, and continuity

BackgroundAnimal-borne telemetry instruments (tags) have greatly advanced our understanding of species that are challenging to observe. Recently, non-recoverable instruments attached to cetaceans have increased in use, but these devices have limitations in data transmission bandwidth. We analyze trade-offs in the longevity, resolution, and continuity of data records from non-recoverable satellite-linked tags on deep-diving Ziphius cavirostris in the context of a behavioral response study of acute noise exposure. We present a strategic data collection programming scheme that balances resolution and continuity against longevity to address specific questions about the behavioral responses of animals to noise exposure in experimental contexts. We compare accuracy and precision between two programming regimes on a commercially available satellite-linked tag: (1) dive behavior summary defined by conductivity thresholds and (2) depth time-series at various temporal resolutions. ResultsWe found that time-series data could faithfully replicate the more precisely defined dives from a dive summary record data stream to an acceptable error range for our application. We determined a 5-minute time-series data stream collected for 14 days balanced resolution with longevity, achieving complete or nearly complete diving records in 6 out of 8 deployments. We increased our data reception rate several fold by employing a boat based data capture system. Finally, a tag deployed in a group concurrently with a high resolution depth recorder showed high depth concordance. ConclusionsWe present the conceptual framework and iterative process for matching telemetry tag programming to research questions that we used and which should be applicable to a wide range of studies. Although designing new hardware for our specific questions was not feasible at the time, we were able to optimize the sampling regime of a commercially available instrument to meet the needs of our research questions and proposed analyses. Nevertheless, for other study species or designs, the complicated intersection between animal behavior and bandwidth of telemetry systems can often create a severe mismatch among research questions, data collection, and analysis tools. More flexible programming and purpose built instruments will increase the efficacy of these studies and increase the scientific yield relative to the inherently higher risk of invasive studies.

animal behavior and cognition↗

bioRxiv2021

An integrated comparative physiology and molecular approach pinpoints mediators of breath-hold capacity in dolphins

Ischemic events, such as ischemic heart disease and ischemic stroke, are the number one cause of death globally. Ischemia prevents blood, carrying essential nutrients and oxygen, from reaching tissues and organ systems, leading to cell and tissue death, and eventual organ failure. While humans are relatively intolerant to these ischemic events, other species, such as marine mammals, have evolved remarkable tolerance to chronic ischemia/reperfusion during diving. Here we capitalized on the unique adaptations of bottlenose dolphins (Tursiops truncatus) as a comparative model of ischemic stress and hypoxia tolerance to identify molecular features associated with breath-holding. Using RNA-Seq we observed time-dependent upregulation of the arachidonate 5-lipoxygenase (ALOX5) gene during breath-holding. Consistent with the RNA-Seq data, we also observed increased ALOX5 enzymatic activity in the serum of dolphins undergoing breath holds. ALOX5 has previously been shown to be activated during hypoxia in rodent models, and its metabolites, leukotrienes, induce vasoconstriction. The upregulation of ALOX5 occurred within the estimated aerobic dive limit of the species, suggesting that ALOX5 enzymatic activity may promote tolerance to ischemic stress through sustained vasoconstriction in dolphins during diving. These observations pinpoint a potential molecular mechanism by which dolphins, and perhaps other marine mammals, have adapted to the prolonged breath-holds associated with diving.

physiology↗