Animal-borne Cameras Research Articles

Behavioral response of megafauna to boat collision measured via animal-borne camera and IMU

Overlap between marine megafauna and maritime activities is a topic of global concern. Basking sharks (Cetorhinus maximus; CM) are listed as Globally Endangered under the IUCN, though reported sightings appear to be increasing in Ireland. While such trends in the region are welcome, increasing spatiotemporal overlap between CM and numerous water users poses an increased risk of boat strikes to the animals. To demonstrate the risk and impact of boat strikes on marine megafauna, we present camera-enabled animal-borne inertial measurement unit (IMU) data from a non-lethal boat strike on a CM within a proposed National Marine Park in Ireland. We tagged a ~7-m female CM in County Kerry, Ireland, which was struck by a boat ~6 h after tag deployment. Comparison of pre-strike data with 4 h of video and ~7.5 h of IMU data following the boat strike provides critical insight into the animal’s response. While the CM reacted momentarily with an increase in activity and swam to the seafloor, it quickly reduced its overall activity (i.e., overall dynamic body acceleration, tailbeat cycles, tailbeat amplitude, and vertical velocity) for the remainder of the deployment. Notably, the animal also ceased feeding for the duration of the video and headed towards deep offshore waters, which is in stark contrast to the pre-strike period where the animal was consistently observed feeding along the surface in shallow coastal water. This work provides insight into a CM’s response to acute injury and highlights the need for appropriate protections to mitigate risks for marine megafauna.

The urban lives of green sea turtles: Insights into behavior in an industrialized habitat using an animal-borne camera.

The cryptic and aquatic life histories of sea turtles have made them a challenging group to directly observe, leaving significant knowledge gaps regarding social behavior and fine-scale elements of habitat use. Using a custom-designed animal-borne camera, we observed previously undocumented behaviors by green turtles (Chelonia mydas) at a foraging area in San Diego Bay, a highly urbanized ecosystem in California, USA. We deployed a suction-cup-attached pop-off camera (manufactured by Customized Animal Tracking Solutions) on 11 turtles (mean straight carapace length = 84.0 ± 11.2 cm) for between 1 and 30.8 h. Video recordings, limited to sunlit hours, provided 73 h of total observation time between May 2022 and June 2023. We observed 32 conspecific interactions; we classified 18 as active, entailing clear social behaviors, as compared with 14 passive interactions representing brief, chance encounters. There was no evidence for agonistic interactions. The camera additionally revealed that green turtles consistently use metal structures within urban San Diego Bay. In seven instances, turtles exhibited rubbing behavior against metal structures, and we observed two examples of turtles congregating at these structures. High rates of intraspecific interaction exhibited relatively consistently among individuals provide a compelling case for sociality for green turtles in San Diego Bay, adding to a growing research base updating their historical label of "non-social." The frequent use of metal structures by the population, in particular the rubbing of exposed skin, has implications for behavioral adaptations to urban environments. Our study exemplifies the promise of technological advances (e.g., underwater and animal-borne cameras) for updating natural history paradigms, even for well-studied populations.

African penguin Spheniscus demersus foraging on juvenile fish in jellyfish tentacles

Technological advances have enabled the observation of foraging behaviour in wild marine animals. We can observe where they go, how deep they dive, how much energy they expend, and with the use of animal-borne cameras we can capture specific foraging behaviours. Here we describe a newly observed foraging behaviour in African Penguins Spheniscus demersus in which they target fish located in jellyfish tentacles. As animal-borne cameras have only been deployed on African Penguins since 2015 it is unclear whether this behaviour is novel or previously unobserved. The behaviour appears to be opportunistic and beneficial to the African Penguins as it enables them to catch stationary prey. As the availability of the African Penguin’s traditional schooling fish prey changes in the southern Benguela Current ecosystem due to climate change and overfishing, opportunistic foraging strategies like this could enable African Penguins to supplement foraging success at a low energetic cost.

Studying the effect of camera tag associated white light on the diving and foraging behavior of Eastern Caribbean sperm whales

Studying the behavior of animals roaming the deep-sea is challenging and is driven by technological developments. The next step to further understand the interactions between predators and prey in the deep sea may be aided by animal-borne camera tags. However, in the darkness of the deep sea, obtaining useful footage requires a light source, which may affect the animal carrying the tag as well as other nearby organisms such as prey. Here we have tested whether the presence of camera associated white light affects the foraging behavior of sperm whales in the Eastern Caribbean Sea. Based on a small dataset of 7 foraging dives with camera lights on, we observed no changes in diving behavior and overall biosonar search behavior. However, we did observed indications of fewer prey capture attempts, which may be due to light induced prey deterrence. For short camera tag deployments this likely does not affect the long term fitness of the whales. However, this effect should be considered and monitored for longer camera tag deployments. Importantly, different deep-sea communities may react differently, we therefore wish to highlight the importance of testing whether research equipment affects the studied animal and its surroundings.

Habitat selection of southern giant petrels: potential environmental monitors of the Antarctic Peninsula

AbstractThe southern giant petrel (Macronectes giganteus) is a widely distributed top predator of the Southern Ocean. To define the fine-scale foraging areas and habitat use of Antarctic breeding populations, 47 southern giant petrels from Nelson Island were GPS-tracked during the summers of 2019–2020 and 2021–2022. Step-selection analysis was applied to test the effects of environmental variables on habitat selection. Visual overlap with seal haul-out sites and fishing areas was also analysed. Birds primarily used waters to the south of the colony in the Weddell and Bellingshausen seas. Females showed a broader distribution, reaching up to -70°S to the west of Nelson Island, while males were mainly concentrated in waters off the northern Antarctic Peninsula. Habitat selection of both sexes was associated with water depth and proximity to penguin colonies. Both overlapped their foraging areas with fishing sites and females in particular overlapped with toothfish fishery blocks in Antarctica and with fishing areas in the Patagonian Shelf. Due to their habitat associations and overlap with fisheries, when harnessed with tracking devices and animal-borne cameras, giant petrels can act as platforms for monitoring the condition and occurrence of penguin colonies, haul-out sites and unregulated fisheries on various temporal and spatial scales in Antarctica.

Energetic consequences of prey type in little penguins (Eudyptula minor).

Investigation of foraging decisions can help understand how animals efficiently gather and exploit food. Prey chase and handling times are important aspects of foraging efficiency, influencing the net energy gain derived from a prey item. However, these metrics are often overlooked in studies of foraging behaviour due to the difficulty in observing them. The present study used animal-borne cameras to investigate the type, duration and energetic consequences of predator-prey interactions in little penguins (Eudyptula minor) (n = 32) from two colonies in Bass Strait, south-eastern Australia. A total of seven main prey items were observed and consumed by little penguins. Penguins were observed to consume prey types and use strategies that have not been previously documented. These included consumption of bellowsfish (Macroramphosus scolopax) and other fish species captured sheltering around jellyfish or extracted dead from the tentacles. Chase and handling time varied with prey type and lasted approximately 2 s for most prey. Profitability varied among prey types, with a greater amount of low profitable prey being consumed, suggesting a trade-off between minimizing energetic costs, and increasing capture rates. These results highlight the use of animal-borne video data loggers to further understand the foraging adaptations of important predators in the marine environment.

Spying the dog: Wearable action camera as a tool to understand dog’s behaviour during homing (Carnivora: Canidae)

Automated data collection methods, such as using GPS collars and animal-borne cameras, represent an efficient way of data collection and may be instrumental in the research of animal orientation, including magnetoreception. In this study, we designed a wearable dog action camera (DAC) system for hunting dogs consisting of a Garmin Virb Elite camera housed in the stainless mount attached to the dog harness. We evaluated the DAC’s reliability and potential to capture various behaviour, and we tested the effect of the DAC on the dog’s activity and well-being. We found no significant impact of the DAC on the dogs’ average speed. The tested system was reliable, efficient and safe for dogs. We recorded various behaviours connected to orientation, such as olfactory behaviour and head scanning, the latter described for the first time in domestic dogs. Furthermore, we observed other important behaviours such as hunting, exploration and comfort behaviour. Using wearable action cameras for studying domestic and free-roaming tame animals can bring new opportunities for future behavioural and sensory ecology research.

Interspecific interactions among three species of sea turtle using a common resting area.

Interspecific interactions among three species of sea turtle using a common resting area.

Predicting foraging dive outcomes in chinstrap penguins using biologging and animal-borne cameras

Abstract Direct observation of foraging behavior is not always possible, especially for marine species that hunt underwater. However, biologging and tracking devices have provided detailed information about how various species use their habitat. From these indirect observations, researchers have inferred behaviors to address a variety of research questions, including the definition of ecological niches. In this study, we deployed video cameras with GPS and time-depth recorders on 16 chinstrap penguins (Pygoscelis antarcticus) during the brood phase of the 2018–2019 breeding season on Signy (South Orkney Islands). More than 57 h of footage covering 770 dives were scrutinized by two observers. The outcome of each dive was classified as either no krill encounter, individual krill or krill swarm encounter and the number of prey items caught per dive was estimated. Other variables derived from the logging devices or from the environment were used to train a machine-learning algorithm to predict the outcome of each dive. Our results show that despite some limitations, the data collected from the footage was reliable. We also demonstrate that it was possible to accurately predict the outcome of each dive from dive and horizontal movement variables in a manner that has not been used for penguins previously. For example, our models show that a fast dive ascent rate and a high density of dives are good indicators of krill and especially of swarm encounter. Finally, we discuss how video footage can help build accurate habitat models to provide wider knowledge about predator behavior or prey distribution.

Prey interactions in tiger sharks: Accounting for visual perception in animal-borne cameras

The ‘evolutionary arms race’ between predator and prey is responsible for many physiological, morphological, and behavioural adaptations and some of the most compelling examples relate to the generation and detection of visual signals. Better understanding of adaptations can arise from approaching predator-prey dynamics from the point of view of the animals themselves, such as through animal-borne cameras. As we learn more about an animal's visual system, we can take this further and analyse visual scenes through their eyes. In this study video cameras mounted on tiger sharks were used to analyse motion cues of sea turtles using two-dimensional motion detector (2DMD) models. Sharks were also equipped with tri-axial motion-sensors to compare visual motion cues to behaviour, using the behavioural metrics of overall dynamic body acceleration (ODBA), path tortuosity, tailbeat frequency and tailbeat acceleration signal amplitude. When comparing the behaviours of sharks in the minute before and after interactions with sea turtles, we found lower ODBA of sharks associated with sea turtles that produced greater visual motion cues. These turtles also invoked swimming by sharks that was more tortuous than when no turtle was encountered. Together, these behaviours suggest that tiger sharks may potentially stalking turtles that produced greater motion cues. Many sea turtles did not stand out from the background motion suggesting they remain motionless as a form of camouflage. This study provides insights into the use of visual cues in prey identification by tiger sharks and the camouflage strategies used by sea turtles to avoid predation.

Characterization of grazing behaviour microstructure using point-of-view cameras.

Grazing patterns, intake structure, and diet selection are dynamic responses to animals’ feeding environment. This study uses video sequences from animal-borne cameras to capture time- and scale-dependent grazing behaviour variables related to sward explanatory conditions. We observed grazing ‘through’ the sheep’s eyes using point-of-view (POV) cameras coupled with event logging software. Time-specific sward features were measured by sampling ‘really’ grazed patches identified by applying a global navigation satellite system (GNSS) precision-grazing approach. Sward variables on a Mediterranean native sward were measured for two years during the active spring plant-growth cycle. Overall, the results demonstrate that POV cameras were able to capture grazing behaviour fine-tuning to changes in sward characteristics. Sheep compensate for the decrease in sward quantity and nutritive value by increasing the size and duration at each behavioural scale (i.e., meal, bout, and station) while increasing the bout rate and decreasing the station rate. Diet composition also changed as sward matured. The proportion of forbs in the diet remained high in early and late spring, and forbs and legumes were preferred to grasses in early spring. Grazing selectivity was more pronounced in late spring, with sheep favouring the middle stratum of the sward’s vertical structure, preferring green vegetative material, while enlarging the feeding niches’ span and spending more time at each niche, consequently reducing the station rate. Although data collected by individual animal-borne POV cameras were representative of the flock behaviour, they may underestimate the total grazing time outside major meals. The results indicate that the use of animal-borne video cameras is suitable for assessing variations in sheep grazing behaviour patterns in complex swards.

Animal-borne video systems provide insight into the reproductive behavior of the Asian black bear.

Previous studies on the mating system of the Asian black bear (Ursus thibetanus) have been limited to observations of captive populations and estimations of multiple paternities. Hence, the mating system of wild bears remains poorly understood. Animal‐borne camera systems (i.e., cameras mounted on animals) provide novel tools to study the behavior of elusive animals. Here, we used an animal‐borne video system to record the activities of wild bears during the mating season. Video camera collars were attached to four adult Asian black bears (male “A” and “B,” and female “A” and “B”) captured in Tokyo, central Japan, in May and June 2018. The collars were retrieved in July 2018, after which the video data were downloaded and analyzed in terms of bear activity and mating behavior. All the bears were found to interact with other uniquely identifiable bears for some of the time (range 9–22 days) during the deployment period (range 36–45 days), and multiple mating in males was documented. Both males and females exhibited different behaviors on social days (i.e., days when the bear interacted with conspecifics) compared with solitary days (i.e., days with no observed interactions with conspecifics). Compared with solitary days, the bears spent a lower proportion of time on foraging activities and higher proportion of time on resting activities on social days. Our results suggest that Asian black bears have a polygamous mating system, as both sexes consort and potentially mate with multiple partners during a given mating season. Furthermore, bears appeared to reduce their foraging activities on social days and engaged more in social interactions.

Animal-borne video reveals atypical behaviour in provisioned green turtles: A global perspective of a widespread tourist activity

Feeding wildlife as a tourist activity is a growing industry around the world. However, providing alternative food sources can affect wildlife ecology and behaviour. In this study, we combined animal-borne cameras on five sub-adult green turtles (Chelonia mydas) from the Bahamas with a global review to directly assess impacts of provisioning on the behaviour of an endangered marine species for the first time. Descriptive evidence from video footage, with videos included in the manuscript, showed that the tagged turtles spent 86% of their time in shallow water (<1.5 m) at a provisioning site. All individuals observed, both tagged and untagged, actively approached people and boats, with up to 10 turtles recorded feeding on squid offered by tourists at one time. During these feeding events, multiple accounts of atypical aggressive behaviour such as biting and ramming conspecifics were recorded. Furthermore, a review of online sources revealed the widespread significance of turtle feeding as a tourist activity in at least 20 locations within the global range of green sea turtles, as well as five locations with regular provisioning of either loggerhead (Caretta Caretta) or hawksbill (Eretmochelys imbracata) turtles. At the majority of the locations, turtles were fed animal matter such as fish scraps and squid. Although sample size limited quantitative analyses, we found indications of relatively high growth rates of two tagged turtles and low seagrass intake rates of all five tagged turtles. Therefore, our results emphasize the need to further investigate the impacts of turtle provisioning on natural foraging behaviour, ecosystem functioning as well as turtle growth rates and health implications. Supplemental feeding may increase habituation and dependency of turtles on humans with risks for turtle conservation. The innovative use of animal-borne camera technology may provide novel insights to behavioural consequences of human-wildlife interactions that can aid in the management and conservation of rare or endangered species.

Multi-predator assemblages, dive type, bathymetry and sex influence foraging success and efficiency in African penguins.

Marine predators adapt their hunting techniques to locate and capture prey in response to their surrounding environment. However, little is known about how certain strategies influence foraging success and efficiency. Due to the miniaturisation of animal tracking technologies, a single individual can be equipped with multiple data loggers to obtain multi-scale tracking information. With the addition of animal-borne video data loggers, it is possible to provide context-specific information for movement data obtained over the video recording periods. Through a combination of video data loggers, accelerometers, GPS and depth recorders, this study investigated the influence of habitat, sex and the presence of other predators on the foraging success and efficiency of the endangered African penguin, Spheniscus demersus, from two colonies in Algoa Bay, South Africa. Due to limitations in the battery life of video data loggers, a machine learning model was developed to detect prey captures across full foraging trips. The model was validated using prey capture signals detected in concurrently recording accelerometers and animal-borne cameras and was then applied to detect prey captures throughout the full foraging trip of each individual. Using GPS and bathymetry information to inform the position of dives, individuals were observed to perform both pelagic and benthic diving behaviour. Females were generally more successful on pelagic dives than males, suggesting a trade-off between manoeuvrability and physiological diving capacity. By contrast, males were more successful in benthic dives, at least for Bird Island (BI) birds, possibly due to their larger size compared to females, allowing them to exploit habitat deeper and for longer durations. Both males at BI and both sexes at St Croix (SC) exhibited similar benthic success rates. This may be due to the comparatively shallower seafloor around SC, which could increase the likelihood of females capturing prey on benthic dives. Observation of camera data indicated individuals regularly foraged with a range of other predators including penguins and other seabirds, predatory fish (sharks and tuna) and whales. The presence of other seabirds increased individual foraging success, while predatory fish reduced it, indicating competitive exclusion by larger heterospecifics. This study highlights novel benthic foraging strategies in African penguins and suggests that individuals could buffer the effects of changes to prey availability in response to climate change. Furthermore, although group foraging was prevalent in the present study, its influence on foraging success depends largely on the type of heterospecifics present.

New approaches to zoology: Plenary 1

Following the first session of the forum, we held a question and answer session facilitated by Paul Willis. The presentations covered by this plenary session were: Unravelling the secret behaviour of animals using animal-borne camera (Catherine Herbert et al. Sydney University)Large-scale, low-cost monitoring of animal spatial movements: Motus and an automated radio-telemetry grid for Australian zoology (Andrea Griffin et al. Newcastle University)Camera trapping advances: into the new millennia (Paul Meek et al. NSW Dept of Primary Industry)Sound recorders and soundscapes (Paul Roe Queensland University of Technology)

Factors influencing prey capture success and profitability in Australasian gannets (Morus serrator).

ABSTRACTKnowledge of the factors influencing foraging efficiency in top predators can provide insights into the effects of environmental variability on their populations. Seabirds are important marine predators foraging in a highly temporally and spatially variable environment. While numerous studies have focussed on search time and its effects on foraging energetics in seabirds, relatively little is known about the factors influencing capture success and prey profitability in these predators. In the present study, animal-borne cameras were used to investigate the chase durations, capture success, handling durations and profitability of prey consumed by Australasian gannets (Morus serrator) (n=95) from two breeding colonies in south-eastern Australia exposed to different oceanographic conditions. Capture success was generally lower when individuals foraged alone. However, foraging in multi-species groups and in high prey densities increased chase time, while larger prey elicited longer handling times. While prey type influenced profitability, high prey density and foraging in multi-species groups was found to lower prey profitability due to increased time expenditure. While previous studies have found group foraging reduces search time, the increased profitability explains why some animals may favour solitary foraging. Therefore, future studies should combine search time and the currently found factors.

A biologging perspective to the drivers that shape gregariousness in dusky dolphins

Knowledge of proximate (causation and development) and ultimate (evolution and survival function) causes of gregariousness is necessary to advance our knowledge of animal societies. Delphinids are among the most social taxa; however, fine-scale understanding of their intra-specific relationships is hindered by the need for underwater observations on individuals. We developed a non-invasive animal-borne camera system with the goal of examining influences on gregariousness in dusky dolphins (Lagenorhynchus obscurus). We analyzed video and diving records from 11 individual dusky dolphins off Kaikoura, New Zealand. We examined the influence of biologger attachment on dolphin behavior and tested hypotheses regarding the effects of physiology, predation, and inter-individual variation on conspecific interactions. Dolphins did not exhibit increased rates of descent or ascent in the minutes immediately following biologger attachment, indicating a lack of behavioral response. Respiration rate was positively related to dive depth and duration, suggesting that diving is energetically expensive for this species. Gregariousness was negatively related to dive depth providing evidence that the physiological constraints of diving are likely to limit social behavior. Calves were not observed more frequently in infant (vs. echelon) position with increasing depth, highlighting the likelihood of other anti-predation strategies (e.g., dilution effect) in mother-calf pairs. We found that gregariousness differed between individuals within similar social groups, suggesting the importance of collecting data at the individual level. The evidence presented herein suggests that the further development of animal-borne camera systems will yield further insight into the mechanisms underlying delphinid social behavior. Dolphins are highly social and thus excellent model species for examining the cause and function of gregariousness. However, their cryptic nature poses a challenge to collecting the fine-scale data at the individual level required to conduct rigorous hypothesis tests. We overcame this obstacle by deploying a non-invasive cutting-edge biologger on free-ranging dusky dolphins to collect information on diving behavior, physiology, gregariousness, and mother-calf strategies. Results indicate that diving is energetically expensive, even to relatively shallow depths, and these costs likely hinder gregariousness at depth. Individual differences in gregariousness were apparent and as expected in this fission-fusion society. Unexpectedly, mother-calf pairs appeared to utilize strategies other than spatial positioning to minimize predation risk. This study advanced knowledge of dolphin social life and helps to improve the degree of data resolution in cetaceans to a level on par with terrestrial studies.

Predation and Risk Behaviors of Free-Roaming Owned Cats in Auckland, New Zealand via the Use of Animal-Borne Cameras.

Free-roaming cats are at increased risk of injuring themselves as well as other domestic and fauna species, yet relatively little is known about the frequency at which risk and predation behaviors occur in a typical day. In this study, cat risk, and predation behavioral information was collected using animal-borne video cameras and global positioning system (GPS) units that were attached to break-free cat collars. The observation period was one to three consecutive days for 37 convenience sampled free-roaming owned cats in Auckland, New Zealand. Video footage was manually reviewed and all predation and risk behavior events were recorded. These included stalking, pursuing, and seizing prey as well as altercations with other cats, ingesting harmful substances, and venturing into hazardous locations such as roads and storm drains. During the observation period, 23 of the 37 cats (62.2%) engaged in a total of 121 predation events. Of these, 40 resulted in successful prey capture with 18 of the 40 captures involving New Zealand native fauna species. Invertebrates were the most common taxa preyed upon (n = 55; 46%), followed by skinks (n = 8; 7%). No mammalian, avian or amphibian prey were captured and no cat took prey back to their residence. A total of 326 risk behaviors were observed for 32 out of the 37 cats (86.5%) with the most common being cats venturing onto the road (n = 132; 41%). Younger cats (aged 1–6 six years) engaged in significantly more predation and risk behaviors than older cats (aged 7 years and above). Sex, breed, number of cats in a household, and geographic location were not found to be predictors of cats' participation in predation or risk behaviors. Given the high frequency of predation and risk behaviors in free-roaming owned cats, it may be beneficial to educate owners about strategies to minimize risk such as housing them indoors, containing them to their properties or monitoring their time spent outdoors.

The use of animal-borne cameras to video-track the behaviour of domestic cats

Free roaming domestic animals can have a profound effect on wildlife. To better understand and mitigate any impact, it is important to understand the behaviour patterns of the domestic animals, and how other variables might influence their behaviour. Direct observation is not always feasible and bears the potential risk of observer effects. The use of animal-borne small video-cameras provides the opportunity to study behaviour from the animal’s point of view. While video-tracking has been used previously to study specific aspects of the behaviour of a species, it has not been used so far to determine detailed time-budgets. The aim of this study was to provide and validate an ethogram based on cat-camera footage collected from 16 cats (Felis catus). The methodology was validated comparing films recorded simultaneously, from both collar-mounted video recorders and hand-held video recorders. Additionally, the inter-observer reliability of scorers was measured. Continuous and instantaneous recording regimes were compared, and behavioural accumulation curves were evaluated to provide further technique recommendations for video-tracking cats. Video-tracking allows scoring of behaviour as reliably as direct observation (linear mixed effects model: t < 0.001, P = 0.99; df = 14 in 7 cats; Cohen's κ = 0.88). Furthermore, inter-observer reliability was high (Cohen's κ = 0.72) and was not significantly different from 0.8 (one-sample t-test: t = 1.15. df = 5, P = 0.30), indicating that the method is not subject to bias in observers. Recommendations are given for the most efficient scoring protocol to reliably record feline behaviour. While the validation was concerned with cat behaviour, the approach can be easily adapted for a variety of domestic species, as well as some captive animals. Video-tracking offers a new avenue to investigate both general time-budgets and more specific behaviours such as foraging or space use from the animal's point of view and in its normal environment, without restrictions to movement. Insights gained through video-tracking will be relevant to various conservation and animal welfare issues.

Patterns and drivers of vertical movements of the large fishes of the epipelagic

Large epipelagic fishes (> 30 kg maximum size) are known to display a variety of patterns of vertical movement. Although advances in the affordability and sophistication of electronic tags now allows researchers to routinely document these patterns, there is no standardised approach to classify these behaviours and investigate their physical and biological drivers. This paper reviews the existing knowledge of the vertical movements of large, epipelagic fishes and the evidence for the underlying factors that structure this behaviour. The review focuses on behaviours occurring at a range of temporal scales, from seconds to years. We propose that patterns of vertical movement in gill-breathing animals of the epipelagic are best characterised by the need to move continuously in a three-dimensional environment while optimising food encounter and energy expenditure, avoiding predators, searching for mates and remaining within the limits imposed by the physical environment on their physiology (notably water temperature and oxygen). Modern biologging technologies that record both the internal (body temperature, heart rate) and external physical environment coupled with direct recording of behaviour from tri-axial sensors and animal-borne cameras offer a new approach to the analysis of drivers of vertical movement. Ultimately, this can provide insights into the evolution of the behaviour and morphology of these animals.