The first International Bio-Logging Science Symposium was held in Tokyo in March 2003. The 2003 Symposium coined the term ‘Bio-Logging’ and spurred international collaborations among scientists working mainly on marine animals. Nearly 20 years had passed since then, and six BLS Symposia have been held worldwide (St. Andrews, Pacific Grove, Hobart, Strasbourg, Konstanz, and Honolulu). ‘Bio-Logging Science’ has now flourished across diverse research fields, not only in marine but also in terrestrial research fields. Holding the 8th BLS Symposium in Tokyo once again was timely, providing an opportunity to reflect on our accomplishments over the past 20 years and to envision the future of Bio-Logging Science.

The 8th International Bio-Logging Science Symposium (BLS8) was held during 4-8 March 2024 in Tokyo, Japan. The BLS8 welcomed 395 on-site participants, and 69 on-line participants from over 33 countries. The symposium concluded with great success!

Junichi Okuyama, BLS8 Organizing Committee

 

Christine Barry PhD candidate at Murdoch University and the Australian Institute of Marine Science, Australia. 

Can you tell us a bit about yourself and your research interests?

I have a love for marine megafauna and data exploration! My research interests include whale sharks, ecophysiology and behaviour. I use tracking devices similar to a ‘Fitbit’ that attach to the dorsal fin of the shark and allow me to measure their tailbeat frequency, watch them through video, and recreate their three-dimensional movements underwater.

What first interested you in this field of research?

During my undergraduate degree at Flinders University, I was fortunate enough to attend two international elective topics, one in South Africa with white sharks, and one in Palau which is home to a large shark sanctuary. This unlocked a curiosity for shark behaviour and has driven my passion to pursue research.

Can you briefly explain the research you presented at BLS8?

At BSL8 I presented results from my PhD research where I found whale sharks use multiple foraging behaviours to thrive in an oligotrophic environment. Video cameras revealed the sharks transition between 6 novel and 6 known foraging behaviours, highlighting their foraging plasticity. From this study we learnt that whale sharks feed more than previously thought, as they balance cost-effective foraging strategies to maximise energetic gain, within energetically poor environments.

How will you continue to build on this research?

Building on this research, I plan to investigate all behaviours of whale sharks at Ningaloo Reef to understand the importance of the aggregation site for this endangered species.

 

Mathilde Chevallay PhD candidate at Centre d’Etudes Biologiques de Chizé, CNRS, France. 

Can you tell us a bit about yourself and your research interests?

I come from the French Alps, where I spent my entire childhood. Passionate about the sea and marine species since I was a child, I left my hometown after the baccalauréat to study marine biology in Brest, Brittany, for five years. During my masters, I did two research internships in the Centre d’Etudes Biologiques de Chizé, where I specialised in the study of the foraging behaviour of diving predators, especially pinnipeds such as fur seals and elephant seals. Following my internships, I started my PhD in 2021 about fine-scale predator-prey interactions in diving predators of the Southern ocean, i.e. elephant seals, fur seals and king penguins. To do so, I use an innovative approach called biologging, which consists of deploying devices on animals to record detailed information on their behaviour and their environment in areas that are normally totally inaccessible to us. Thanks to these recording devices, we can now have access to a whole new range of information on the life at sea of these mysterious and charismatic deep-diving predators. In particular, the aim of my PhD is to better understand how these deep-diving predators detect, select and capture their prey in the deep and unlit waters of the Southern ocean, and to study the impact of environmental parameters on the distribution and behaviour of their prey, in order to better anticipate the effects of climate change, particularly intense in the polar areas, on the ability of these predators to efficiently find and capture their prey.

What first interested you in this field of research?

Since my childhood, I am very curious about how and why animal behave the way they do. In particular, I have always been fascinated about how animals sense and perceive their environment, and how they use the information they obtain from their environment to move through space, to find their food, to avoid predators and to make decisions that allow them to survive in their complex environments. I remember spending hours following my cat around the garden with a notebook to record his behaviour. He was not a good hunter, but I loved watching him explore his environment, choosing his ‘prey’ and figuring out, or at least trying to figure out, how to catch them. Even if I grew up away from the sea, marine animals particularly intrigued me because, unlike my cat, you cannot just follow them and observe them directly, and I really wanted to know what they do when they are in the deep ocean! When I was doing my bachelor, I met Christophe Guinet, one of my PhD supervisor specialised in the foraging behaviour of deep-diving predators of the Southern ocean, and his research was perfectly in tune with what interested me: understand how predators find and capture their prey in the deep ocean. This is where it all started.

Can you briefly explain the research you presented at BLS8?

I presented the research I conducted during the first two years of my PhD. The aim of this work was to describe the fine-scale predator-prey interactions in two diving predators of the Southern ocean: the Antarctic fur seal and the Southern elephant seal. These two sympatric pinnipeds are both foraging on the same type of prey: small lanternfish. However, they are very different in term of morphology, physiology, diving capacities and locomotor performances so they probably will not hunt their prey in the same way. The Southern elephant seal is a very good diver but slow and not very manoeuvrable; conversely the Antarctic fur seal is a poor diver, but very manoeuvrable and able to accelerate quickly. Therefore, our aim was to better understand how these very different predators can efficiently exploit the same kind of prey.

We deployed sonar tags on these two species, which allowed us to follow the fine-scale behaviour of individuals; with active acoustics, that can scan every prey encountered by the predator during their hunting periods and give us precious information on their prey characteristics and behaviour. Data collected on nine female elephant seals and eight female Antarctic fur seals allowed us to accurately describe the sequence of events starting from the prey detection to prey capture.

We showed that elephant seals detect their prey up to 10 s before the strike, allowing them to approach their prey stealthily without triggering an escape reaction, just like big cats that catch their prey by surprise. This ability of elephant seals to detect their prey in advance likely allow them to reduce the risk of initiating a prey pursuit, and therefore can explain how these massive predators can efficiently catch their small prey in apnoea without spending too much energy. Fur seals and their prey detect each other at the same time, i.e. 1-2 seconds before the strike, which means that fur seals are forced to perform fast manoeuvres to catch their prey before their prey get out of reach. Therefore, we show that our two very different predators rely on distinct hunting strategies according to their locomotor performances, manoeuvrability, and sensory capacities, allowing us to better understand how they can efficiently capture the same kind of prey.

How will you continue to build on this research?

I am in in the middle of my last year of my PhD so I have completed most of the analyses I wanted to do during my thesis and I am starting to write my dissertation. I am now thinking about what I want to do next and what aspects of research I want to explore. The results obtained during my thesis open up a whole range of questions that I would like to explore in more details. In particular, I would like to study the inter-individual differences that can be observed within animal populations. The way in which these differences between individuals emerge within a population, why they emerge, how they are maintained and transmitted and how they will impact on the survival of individuals, their ability to reproduce and therefore population dynamics in the longer term are questions that I am particularly interested in and that I hope to address in my future research projects.

 

Don-Jean Léandri-Breton Università degli Studi di Milano, Italy. 

Can you tell us a bit about yourself and your research interests?

My research interests center on movement ecology and life-history trade-offs throughout the annual life cycle of iteroparous species. I focus primarily on migration behavior and large-scale distribution, influenced by biotic interactions, environmental conditions, and individual decision-making processes. I specialize in avian movement, particularly within Arctic systems. Since my first field season up North during my undergraduate studies, I couldn’t imagine spending summers anywhere else but above the Arctic Circle. I grew to love this challenging yet captivating environment and the migratory species within it, many of which travel vast distances throughout their annual life cycle to exploit this highly seasonal environment. Over the past years, I’ve had the chance to join several expeditions to the Canadian and Russian Arctic, Svalbard, and Alaska, where I learned skills in capturing and tracking animals from various taxa (including shorebirds, seabirds, raptors, foxes, narwhals, and sharks). Notably, I developed expertise in analyzing light-level geolocation (GLS) data to investigate animal migratory movements. My doctoral research focuses on interactions between different stages of the annual life cycle of seabirds – reproduction, migration, and wintering – and how these interactions are influenced by endocrinological, energetical, ecotoxicological and behavioral mechanisms. I used light-level geolocation loggers attached to birds to track their movement throughout the year and combined this with demographic and physiological data collected at a seabird colony in Svalbard (High Arctic Norway).

Can you briefly explain the research you presented at BLS8?

I seized the opportunity to present my latest findings last March at the Biologging Science International Symposium in Tokyo, Japan. I investigated the relative importance of carry-over effects and individual quality in determining cross-seasonal interactions and fitness consequences in migratory seabirds (black-legged kittiwakes, Rissa tridactyla). To achieve this, I utilized 13 years of reproduction monitoring and annual movement data of kittiwakes to estimate their fitness, distribution, and winter energy expenditure. I combined this long-term dataset with an experimental approach (experimentally induced breeding failure) to discern true carry-over effects from individual quality. Piecewise path analyses unveiled positive interactions between consecutive annual life stages; individuals breeding successfully one year exhibited lower energy expenditure in winter and higher breeding success the following year. This suggested that individual quality predominantly determined seasonal interactions in the study population. However, controlling experimentally for individual quality revealed underlying carry-over effects otherwise masked by quality, with breeding costs manifesting as increased energy expenditure, delayed reproduction, and lower breeding success.

How will you continue to build on this research?

Having just defended my thesis successfully, I’ve started a postdoctoral position at the University of Milan, this time investigating polymorphic strategies in a partially migratory seabird. This work brings me North again, this time to Alaska. Thus, I’ll continue delving into animal migration, one of Nature’s most impressive phenomena. Migratory species serve as vital connectors between Arctic regions and the rest of the world. Understanding changes in breeding populations in the North necessitates a profound understanding of how conditions experienced by individuals further south can reverberate through subsequent stages of their annual life cycle. It is this general goal that will provide a direction to my research in the future.

 

Ellen Hayward Masters Student at University of St Andrews, UK. 

Can you tell us a bit about yourself and your research interests?

I am a Research Masters student in the School of Biology at the University of St Andrews, within the Sea Mammal Research Unit (SMRU). I am originally from France and moved to Scotland for my undergraduate degree at St Andrews. My work consists of utilising animal-borne video data in combination with other biologging sensors to gain insight into marine mammals’ underwater behaviour. Currently I am working on obtaining prey capture rates for North Atlantic herring-feeding killer whales (Orcinus orca) using synchronised acoustic and video data loggers.

What first interested you in this field of research?

Animal-borne video loggers can reveal aspects of marine mammal behaviour which cannot be detected by other biologging sensors, enabling direct and continuous underwater behavioural observations. I am especially drawn to the use of video data to ground-truth data recorded by other biologging sensors, permitting novel analyses of extensive past datasets. This is of particular interest to me in the context of my research project, in which I am using video to ground-truth acoustic indicators of prey capture, to obtain prey capture rate estimates. I am greatly motivated by the potential implications of this research to better the understanding of marine mammal’s energetic balance and requirements, as well as the impacts of their prey acquisition on the ecosystem they inhabit.

Can you briefly explain the research you presented at BLS8?

At the BLS8, I presented the results of an exploratory study which aimed to characterise a novel acoustic indicator of prey capture in herring-feeding North Atlantic killer whales, termed ‘slurping’, and develop a method to quantify prey capture rate using this sound. I utilised synchronised acoustic and video data records, which permitted the direct association of ‘slurps’ with video observations of prey captures by specific individuals. Using slurps produced by tagged individuals, I evaluated how far away from their source these sounds could be detected by logger hydrophones. I then determined the proportion of video-confirmed prey captures which were accompanied by a slurp, which I used to estimate the number of prey captures by entire foraging groups during each foraging event. These methods have the potential to be further developed and applied to larger datasets, to obtain wider-scale and more accurate estimates of prey capture in North Atlantic herring-feeding killer whales. These estimates could be valuable within ecosystem and fisheries management contexts.

How will you continue to build on this research?

The next step of this study is to increase the sample size of this analysis, with data collected both in Iceland and Norway in 2023 (and hopefully 2024). With this larger dataset, I aim to improve the reliability and generalisability of the estimation methods developed in the project I presented at the BLS8. As part of this, I plan to further develop this method to enable estimations of prey capture rate solely from acoustic data, which would allow the analysis of available acoustic records dating back to 2005. I will then compare prey capture rates both geographically and temporally, to see whether prey capture rates differ between Icelandic and Norwegian killer whales, as well as how these have changed over the past 20 years in both locations.