1. The paradigm-changing opportunities of biologging sensors for ecological research, especially movement ecology, are vast, but the crucial questions of how best to match the most appropriate sensors and sensor combinations to specific biological questions and how to analyse complex biologging data, are mostly ignored.2. Here, we fill this gap by reviewing how to optimize the use of biologging techniques to answer questions in movement ecology and synthesize this into an Integrated Biologging Framework (IBF).3. We highlight that multisensor approaches are a new frontier in biologging, while identifying current limitations and avenues for future development in sensor technology.4. We focus on the importance of efficient data exploration, and more advanced multidimensional visualization methods, combined with appropriate archiving and sharing approaches, to tackle the big data issues presented by biologging. We also discuss the challenges and opportunities in matching the peculiarities of specific sensor data to the statistical models used, highlighting at the same time the large advances which will be required in the latter to properly analyse biologging data.

Biologging devices are used ubiquitously across vertebrate taxa in studies of movement and behavioural ecology to record data from organisms without the need for direct observation. Despite the dramatic increase in the sophistication of this technology, progress in reducing the impact of these devices to animals is less obvious, notwithstanding the implications for animal welfare. Existing guidelines focus on tag weight (e.g. the ‘5% rule'), ignoring aero/hydrodynamic forces in aerial and aquatic organisms, which can be considerable. Designing tags to minimize such impact for animals moving in fluid environments is not trivial, as the impact depends on the position of the tag on the animal, as well as its shape and dimensions. We demonstrate the capabilities of computational fluid dynamics (CFD) modelling to optimize the design and positioning of biologgers on marine animals, using the grey seal (Halichoerus grypus) as a model species. Specifically, we investigate the effects of (a) tag form, (b) tag size, and (c) tag position and quantify the impact under frontal hydrodynamic forces, as encountered by seals swimming at sea. By comparing a conventional versus a streamlined tag, we show that the former can induce up to 22% larger drag for a swimming seal; to match the drag of the streamlined tag, the conventional tag would have to be reduced in size by 50%. For the conventional tag, the drag induced can differ by up to 11% depending on the position along the seal's body, whereas for the streamlined tag this difference amounts to only 5%. We conclude by showing how the CFD simulation approach can be used to optimize tag design to reduce drag for aerial and aquatic species, including issues such as the impact of lateral currents (unexplored until now). We also provide a step‐by‐step guide to facilitate the implementation of CFD in biologging tag design.

Colonial pinnipeds may be subject to substantial consumptive competition because they are large, slow-moving central place foragers. We examined possible mechanisms for reducing this competition by examining the diving behaviour of harbour seals (Phoca vitulina) after equipping 34 seals (11 females, 23 males) foraging from three locations; Rømø, Denmark and Lorenzenplate and Helgoland, Germany, in the Wadden Sea area with time-depth recorders. Analysis of 319,021 dives revealed little between-colony variation but appreciable inter-sex differences, with males diving deeper than females, but for shorter periods. Males also had higher vertical descent rates. This result suggests that males may have higher overall swim speeds, which would increase higher oxygen consumption, and may explain the shorter dive durations compared to females. Intersex variation in swim speed alone is predicted to lead to fundamental differences in the time use of three-dimensional space, which may help reduce consumptive competition in harbour seals and other colonial pinnipeds.

Colonial pinnipeds may be subject to substantial consumptive competition because they are large, slow-moving central place foragers. We examined possible mechanisms for reducing this competition by examining the diving behaviour of harbour seals (Phoca vitulina) after equipping 34 seals (11 females, 23 males) foraging from three locations; Rømø, Denmark and Lorenzenplate and Helgoland, Germany, in the Wadden Sea area with time-depth recorders. Analysis of 319,021 dives revealed little between-colony variation but appreciable inter-sex differences, with males diving deeper than females, but for shorter periods. Males also had higher vertical descent rates. This result suggests that males may have higher overall swim speeds, which would increase higher oxygen consumption, and may explain the shorter dive durations compared to females. Intersex variation in swim speed alone is predicted to lead to fundamental differences in the time PrePrints 25 but for shorter periods. Males also had higher vertical descent rates. This result suggests that males 26 may have higher overall swim speeds, which would increase higher oxygen consumption, and may 27 explain the shorter dive durations compared to females. Intersex variation in swim speed alone is 28 predicted to lead to fundamental differences in the time use of three-dimensional space, which may 29 help reduce consumptive competition in harbour seals and other colonial pinnipeds. 35 • Both sexes increased dive duration with depth but females dived proportionately longer. 36 • Males had higher descent and ascent rates than females. 37 • It is suggested that apparently higher swim speed in males may constrain dive duration. 38PeerJ PrePrints | https://dx

With the increasing threats of climate change, there is an ever-pressing need to reduce fossil fuel emissions. Thus, recent years have seen a dramatic increase in the development of marine renewable energy (MRE) devices – in particular tidal stream turbines (TSTs) – to exploit tidal stream environments (TSEs) for green electricity generation. However, TSTs may pose threats to marine megafauna and relatively little is known about how animals operate in the environments targeted by these devices, and how they may be affected by them. This information is crucial for informing appropriate management strategies to mitigate the risk of conflict between animals and TST developments. Here, using grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) as my study species, with data collected from around the UK and neighbouring waters, including the Celtic and the North Sea, I aim to understand and quantify how seals move in TSEs and the implications of this for the TST industry. To achieve this, I quantify the broad-scale movement patterns of seals in coastal waters and their overlap with TSTs, examine the fine-scale movement and behaviour of seals in response to tidal conditions, derive recommendations on sample size and recording duration for animal tracking studies, and design new tags to track seals in TSEs at very fine-scales whilst minimising tag impact. My results suggest that the movements and behaviour of seals are driven by a combination of measurable (and in some cases predictable) demographic and environmental factors, and that the conservation strategies developed to manage the interaction between individuals and populations with TST devices must consider site-specific differences and account for individual variation, with consequences regarding data requirements. Further investigation is required to fully elucidate the extent of variability of seal movements in TSEs and the threats of TST developments, however the research presented herein provides new tools and ecological insights to support this need for both researchers and practitioners.