Flash and grab : deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey

Funding: Fondation BNP Paribas; Centre National d'Etudes Spatiales; Institut Polaire Français Paul Emile Victor; Natural Environment Research Council; H2020 Marie Skłodowska-Curie Actions.Bioluminescence, which occurs in approximately 80% of the world's mesopelagic fauna, can take the form of a low-intensity continuous glow (e.g. for counter-illumination or signalling) or fast repetitions of brighter anti-predatory flashes. The southern elephant seal (SES) is a major consumer of mesopelagic organisms, in particular the abundant myctophid fish, yet the fine-scale relationship between this predator's foraging behaviour and bioluminescent prey remains poorly understood. We hypothesised that brief, intense light emissions should be closely connected with prey strikes when the seal is targeting bioluminescent prey that reacts by emitting anti-predator flashes. To test this, we developed a biologging device containing a fast-sampling light sensor together with location and movement sensors to measure simultaneously anti-predator bioluminescent emissions and the predator's attack motions with a 20 ms resolution. Tags were deployed on female SES breeding at Kerguelen Islands and Península Valdés, Argentina. In situ light levels in combination with duration of prey capture attempts indicated that seals were targeting a variety of prey types. For some individuals, bioluminescent flashes occurred in a large proportion of prey strikes, with the timing of flashes closely connected with the predator's attack motion, suggestive of anti-predator emissions. Marked differences across individuals and location indicate that SES do exploit bioluminescent organisms but the proportion of these in the diet varies widely with location. The combination of wideband light and acceleration data provides new insight into where and when different prey types are encountered and how effectively they might be captured.Publisher PDFPeer reviewe

Dare to differ : individual foraging success in marine predators, from the largest seal to small penguins

The oceans are undergoing rapid alterations due to human activities, making it crucial to predict how ecosystem shifts will affect marine predators. Short-term indicators of the fitness consequences of a changing environment, such as individual foraging performance, are essential to guide timely conservation measures but there is a dearth of methods for quantifying the individual foraging strategies and efficiency of aquatic animals. This thesis documents the development of three innovative multi-sensor biologging devices and explores their application to uncover the foraging performance of Southern Ocean predators. A tag containing wide-bandwidth light and movement sensors was developed to measure anti-predator bioluminescent signals emitted by prey as they are hunted by southern elephant seals. Results indicate that some seals target large aggregations of bioluminescent prey, but inter-individual variability is wide. The need for details on the prey size, quality and ease of capture prompted the development of a miniature sonar and movement tag to study both the biotic environment of marine predators and their feeding interactions. Using proxies for prey type, behaviour and capture success, I identified prey types associated with differing rates of body condition improvement in southern elephant seals, providing evidence in marine predators that individual prey selection strategies are linked with longer-term energy gains. A miniature sound and movement tag was developed to record foraging and provisioning behaviour of macaroni penguins and to examine how performance in daily feeding trips influenced subsequent chick provisioning. Using the same device, I combined proxies for swimming speed, posture and foraging activity to infer prey types in the Antarctic fur seal and explored individual foraging performance in years of contrasting prey availability. These new methods are applicable to a range of marine predators while the ecological results provide key information to help predict population trajectories under changing climate and fisheries scenarios."This work was funded by the Natural Environmental Research Council (grant number NE/N012070/1] and the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland, funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions) and their support is gratefully acknowledged."--Fundin

Flash and grab: deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey (dataset)

Data set in support of the paper: ‘Flash and grab: deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey’ by Pauline Goulet, Christophe Guinet, Claudio Campagna, Julieta Campagna, Peter Lloyd Tyack and Mark Johnson published in J Exp Biol (2020). Data were obtained from a biologging device containing a fast-sampling light sensor together with location and movement sensors deployed on female southern elephant seals at Kerguelen Islands and Peninsula Valdes (Argentina). The data subset comprises 5 days from each animal and includes time series for depth, jerk and light, sampled at 50Hz. The data for each animal is in a NetCdf format file containing the variables: info (deployment ID, seal ID, deployment start date, data provider, study species, deployment location), J (root mean square of the vector magnitude of the rate of change in the 3-axis acceleration along with information on sampling rate, measurement unit, cropping factor), P (calibrated and offset-corrected pressure data along with information on sampling rate, measurement unit, cropping factor) and LL (corrected light data along with information on sampling rate, measurement unit, cropping factor). See www.animaltags.org for more information about this format and for tools to explore the data

A miniature biomimetic sonar and movement tag to study the biotic environment and predator-prey interactions in aquatic animals

International audienceHow predators find, select and capture prey is central to understanding trophic cascades and ecosystem structure.But despite advances in biologging technology, obtaining in situ observations of organisms and their interactionsremains challenging in the marine environment. For some species of toothed whales, echoes fromorganisms insonified by echolocation clicks and recorded by sound logging tags have provided a fine-scale viewof prey density, and predator and prey behaviour during capture attempts, but such information is not availablefor marine predators that do not echolocate. Here the development and performance of a miniature biomimeticsonar and movement tag capable of acquiring similar data from non-echolocating marine predators is reported.The tag, weighing 200 g in air, records wide bandwidth sonar data at up to 50 pings a second synchronously withfast-sampling sensors for depth, acceleration, magnetic field and GPS. This sensor suite enables biotic conditionsand predator behaviour to be related to geographic location over long-duration foraging trips by apex marinepredators. The sonar operates at 1.5 MHz with a 3.4° beamwidth and a source level of 190 dB re 1 μPa at 1 m.Sonar recordings from a trial deployment of the tag on a southern elephant seal contained frequent targetscorresponding to small organisms up to 6m ahead of the tagged animal. Synchronously sampled movement dataallowed interpretation of whether the seal attempted to capture organisms that it approached closely while thehigh sonar ping rate revealed attempts by prey to escape. Results from this trial demonstrate the ability of the tagto quantify the biotic environment and to track individual prey captures, providing fine-scale information onpredator-prey interactions which has been difficult to obtain from non-echolocating marine animals

A miniature biomimetic sonar and movement tag to study the biotic environment and predator-prey interactions in aquatic animals

How predators find, select and capture prey is central to understanding trophic cascades and ecosystem structure. But despite advances in biologging technology, obtaining in situ observations of organisms and their interactions remains challenging in the marine environment. For some species of toothed whales, echoes from organisms insonified by echolocation clicks and recorded by sound logging tags have provided a fine-scale view of prey density, and predator and prey behaviour during capture attempts, but such information is not available for marine predators that do not echolocate. Here the development and performance of a miniature biomimetic sonar and movement tag capable of acquiring similar data from non-echolocating marine predators is reported. The tag, weighing 200 g in air, records wide bandwidth sonar data at up to 50 pings a second synchronously with fast-sampling sensors for depth, acceleration, magnetic field and GPS. This sensor suite enables biotic conditions and predator behaviour to be related to geographic location over long-duration foraging trips by apex marine predators. The sonar operates at 1.5 MHz with a 3.4° beamwidth and a source level of 190 dB re 1  μPa at 1 m. Sonar recordings from a trial deployment of the tag on a southern elephant seal contained frequent targets corresponding to small organisms up to 6 m ahead of the tagged animal. Synchronously sampled movement data allowed interpretation of whether the seal attempted to capture organisms that it approached closely while the high sonar ping rate revealed attempts by prey to escape. Results from this trial demonstrate the ability of the tag to quantify the biotic environment and to track individual prey captures, providing fine-scale information on predator-prey interactions which has been difficult to obtain from non-echolocating marine animals

A novel animal-borne miniature echosounder to observe the distribution and migration patterns of intermediate trophic levels in the Southern Ocean

International audienceDespite expanding in-situ observations of marine ecosystems by new-generation sensors, information about intermediate trophic levels remains sparse. Indeed, mid-trophic levels, while encompassing a broad range of zooplankton and micronekton organisms that represent a key component of marine ecosystems and sustain large and diverse communities of marine predators, are challenging to sample and identify. In this study, we examined whether an animal-borne miniature active echosounder can provide information on the distribution and movements of mid-trophic level organisms. If so, such a sonar tag, harnessing the persistent diving behaviour of far-ranging marine mammals, could greatly increase the density of data on this under-studied biome. High-frequency (1.5 MHz) sonar tags were deployed simultaneously with oceanographic tags on two southern elephant seals (Mirounga leonina), at the Kerguelen Islands and Valdés Peninsula (Argentina), and recorded acoustic backscatter while the seals foraged respectively in the Indian and the Atlantic sectors of the Southern Ocean. The backscatter varied widely over time and space, and the seals attempted to capture only a small fraction of the insonified targets. Diel vertical migration patterns were clearly identifiable in the data, reinforcing our confidence in the ability of the sonar tags to detect living mid-trophic organisms along with possibly sinking biological detritus. Moreover, CTD tags attached to the same animals indicated how the abundance, size distribution, and diel migration behaviour of acoustic targets varied with water bodies. These preliminary results demonstrate the potential for animal-borne sonars to provide detailed in-situ information. Further validation effort will make it a valuable tool to refine the estimation of carbon export fluxes as well as for assessing the variation of mid-trophic level biomass according to oceanographic domains and seasons

Sea-ice edge is more important than closer open water access for foraging Adélie penguins: evidence from two colonies

International audienceSentinel species, like Adélie penguins, have been used to assess the impact of environmental changes, and their link with sea ice has eceived considerable attention. Here, we tested if foraging Adélie penguins from 2 colonies in East Antarctica target the distant sea-ice edge or take advantage of closer open waters that are readily available near their colony. We examined the foraging behaviour of penguins during the incubation trips of females in 2016 and males in 2017, using GPS tracking and diet data in view of daily sea-ice data and bathymetry. In 2016−2017, sea-ice cover was extensive during females’ trips but flaw leads and polynyas were close to both study sites. Sea ice receded rapidly during males’ trips in 2017−2018. Despite close open water near both colonies in both years, females and males preferentially targeted the continental slope and the sea-ice edge to forage. In addition, there was no difference in the diet of penguins from both colonies: all penguins fed mostly on Antarctic krill and males also foraged on Antarctic silverfish. Our results highlight the importance of the sea-ice edge for penguins, an area where food abundance is predictable. It is likely that resource availability was not sufficient in closer open water areas at such an early stage in the breeding season. The behaviours displayed by the penguins from both colonies were similar, suggesting a common behaviour across colonies in Terre Adélie, although additional sites would be necessary to confirm this hypothesis

Spies of the deep: an animal-borne active sonar and bioluminescence tag to characterise mesopelagic prey size and behaviour in distinct oceanographic domains

Abstract Mesopelagic fish, a central component of marine trophic networks, play a fundamental role in marine ecosystems. However, as they live in highly inaccessible environments, little information is currently available on their ecology, especially on the influence of oceanographic parameters on their distribution. The emergence of biologging technologies has made it possible to use deep-diving predators as bio-samplers of their environment in under-sampled regions. In this work, we deployed an innovati ve miniaturised sonar tag that combines active acoustics with high-resolution GPS, pressure, movement and light sensors on Southern elephant seals, a deep-diving predator feeding on mesopelagic prey. Seals were also equipped with oceanographic tags, allowing us to explore the functional relationships between oceanographic parameters, distribution and ecology of mesopelagic prey targeted by seals and the seals’ foraging behaviour. We highlighted strong vertical differences in prey characteristics and behaviour, with larger, more evasive and less bioluminescent prey in deeper waters. Moreover, prey encountered in warmer waters were found deeper, were more evasive and displayed a more marked diel vertical migration behaviour compared to prey encountered in colder waters, suggesting that prey accessibility and characteristics differ according to oceanographic domains. This study highlights the usefulness of the sonar-bioluminescence tag to infer mesopelagic prey distribution and habitat when deployed on deep-diving predators such as elephant seals

Spies of the deep: An animal-borne active sonar and bioluminescence tag to characterise mesopelagic prey size and behaviour in distinct oceanographic domains

International audienceMesopelagic fishes, a central component of marine trophic networks, play a fundamental role in marine ecosystems.However, as they live in highly inaccessible environments, little information is currently available ontheir distribution and abundance. The emergence of biologging technologies has made it possible to use deepdivingpredators as bio-samplers of their environment in under-sampled regions. In this work, we deployed aninnovative miniaturised sonar tag that combines active acoustics with high-resolution GPS, pressure, movementand light sensors on Southern elephant seals, a deep-diving predator feeding on mesopelagic prey. Seals werealso equipped with Conductivity-Temperature-Depth tags. Salinity and temperature depth profiles were used todefine oceanographic domains, allowing us to explore distribution and ecology of mesopelagic prey targeted byseals and the seals’ foraging behaviour. We highlighted strong vertical differences in prey characteristics andbehaviour, with larger, more evasive and less bioluminescent prey in deeper waters. Moreover, prey encounteredin warmer waters were found deeper, were more evasive and displayed a more marked diel vertical migrationbehaviour compared to prey encountered in colder waters, suggesting that prey accessibility and characteristicsdiffer according to oceanographic domains. This study highlights the usefulness of the sonar-bioluminescence tagto infer mesopelagic prey distribution and habitat when deployed on deep-diving predators such as elephantseals