ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Maevatiana Ratsimbazafindranahaka is an author on ‘ Behavioral data suggest adaptive buoyancy control during shallow dives in humpback whales’, published in JEB. Maevatiana conducted the research described in this article while a PhD Candidate in Dr Isabelle Charrier's lab at Institut des Neurosciences Paris-Saclay, Université Paris-Saclay, France. Maevatiana is now a Postdoc (Alexander von Humboldt postdoctoral research fellow) in the lab of Prof. Dr Meg Crofoot at Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Germany, investigating animal communication, social interactions and cognition, integrating bioacoustics and multi-sensor tags to study behavior in natural settings.
Maevatiana Ratsimbazafindranahaka
How did you become interested in biology?
As a child, I was naturally curious about how and why things work, especially in the animal kingdom. I was fascinated by animals, why they behave the way they do, why they look the way they do and how they manage to accomplish certain feats, starting with the animals I could find in our yard. Sometimes, I even wondered about my own place among Earth's many life forms. I spent hours at the local library, flipping through books, wondering about the natural world, and sometimes simply gazing at wildlife pictures. Eventually, I knew I wanted to work with animals. Still, at the time, I had no idea what kind of career that would be, especially since biology and academia weren't common career paths where I grew up.
Describe your scientific journey and your current research focus
I was among the few in my class who, after earning my baccalauréat (the equivalent of a high school diploma), decided to pursue biology at university, while most of my peers chose other fields. I completed my undergraduate studies at the University of Antananarivo, Madagascar, focusing on organisms and ecosystems biology. While not entirely specialized in animal biology, the program provided a strong foundation in ecology and biodiversity. I then pursued a master's degree in animal biology and conservation, also at the University of Antananarivo. For my master's internship, I studied maternal dependence in humpback whales; close enough to my favorite animal, the killer whale, I suppose! (Especially considering that the other options included chameleons, birds, and lemurs.) This experience introduced me to the tools used to study whale behavior underwater. I found it fascinating that we could simply attach recording devices to animals and let them live their lives without further interference. This approach captivated me and motivated me to continue with a PhD focused on bio-logging and bioacoustics. With the support of those who would later become my PhD supervisors, I applied for a joint PhD between Paris-Saclay University (Paris-Saclay Institute of Neuroscience, France) and the University of Antananarivo (Department of Zoology and Animal Biodiversity, Madagascar). This was a fantastic opportunity to broaden my horizons while maintaining ties with my home country. My research focused on mother–calf interactions in humpback whales. Looking at my academic path, it might seem like I worked exclusively on marine mammals, but in reality, I also studied small mammals and frogs in parallel, particularly in conservation and applied science contexts. After my PhD, I joined Cerema (‘Centre for Studies and Expertise on Risks, the Environment, Mobility and Urban Planning’, France) to gain more experience in acoustics. Later, I was awarded the Alexander von Humboldt Postdoctoral Fellowship, which led me to the Max Planck Institute of Animal Behavior (Germany), where I am currently based. My research now focuses on group behavior and vocal communication in Verreaux's sifaka, a lemur species. This project is a great opportunity for me to expand my expertise in using animal-borne tags beyond marine species and into terrestrial mammals.
How would you explain the main findings of your paper to a member of the public?
We often think of marine mammals as experiencing passive changes in buoyancy as they dive due to variations in ambient pressure. This happens because air-filled organs, especially the lungs, compress as pressure increases with depth. Near the surface, where pressure is lower, the air in the lungs creates positive buoyancy, helping the animal float. As the animal descends, the lungs compress, reducing air volume, which shifts their buoyancy from positive to neutral and eventually negative (sinking). Because of this, marine mammals must exert more effort to descend than ascend when they are close to the surface, as they must overcome their natural buoyancy. At greater depths, however, the opposite occurs: they expend less effort going down but more effort coming back up.
This pattern has been documented in various species, particularly pinnipeds (like seals) and toothed whales (like dolphins). However, our study on humpback whales suggests that baleen whales may be an exception, at least at shallow depths. Unlike other marine mammals, humpback whales appear to move up and down in the water with low effort, regardless of depth. They can also adjust the depth at which they are neutrally buoyant. For example, they can remain suspended at 5 m as well as at 30 m. They can also transition between depths within the same dive with almost no visible external effort. This suggests that humpback whales can actively control their buoyancy, using it to their advantage for vertical movement in the water column. One possible explanation lies in their unique respiratory system.
Unlike other marine mammals, baleen whales possess an additional air sac (the laryngeal sac) connected to the lungs. Their entire respiratory system has anatomical features that may isolate it from ambient pressure and allow voluntary expansion or compression of the air to fine-tune buoyancy. This could enable them to control their position in the water column much like a fish using a swim bladder, though through a completely different physiological mechanism.
A particularly intriguing finding from our study is that humpback whale calves lack this ability. This highlights yet another critical role of the mother: helping her calf manage buoyancy until it develops the ability to do so independently.
Successful deployment of a multi-sensor tag on a humpback whale calf. The tag records acceleration, pressure, sound and other key data, allowing the reconstruction of whale behavior underwater. A slow and careful tagging approach is adopted.
Successful deployment of a multi-sensor tag on a humpback whale calf. The tag records acceleration, pressure, sound and other key data, allowing the reconstruction of whale behavior underwater. A slow and careful tagging approach is adopted.
What do you enjoy most about research, and why?
What I love most about research is the intellectual challenge. It constantly pushes me to think in new ways. No two problems are ever the same, which keeps things exciting (and sometimes a little overwhelming!). But that's what makes it so stimulating. I also find it deeply rewarding to know that, even in a small way, I'm contributing to something much bigger: expanding our collective understanding of the world. Whether or not the findings have immediate application, adding even a tiny piece to the puzzle of knowledge feels meaningful. When it comes to studying animals, what excites me most is the chance to spark curiosity and fascination in others. I truly believe that curiosity is the first step toward action. The more people are amazed by the natural world, the more likely they are to care about it and, ultimately, to protect it.
What is the most important piece of equipment for your research, what does it do and what question did it help you address?
The most important piece of equipment for my research is the animal-borne tag we use. Studying animals in their natural habitat is challenging because we can't always follow them continuously. This is especially true for whales, as most of their lives happen underwater, beyond our sight. The tag allows us to record crucial data about their movements, the sounds they make and even aspects of their environment. By processing these data, we can infer what the animals are doing and explore behavioral questions that would be impossible to answer through direct observation alone. In a way, using a tag is like giving a whale a smartphone. Just like the sensors in our phones (accelerometers, magnetometers and more) allow apps to track our movements throughout the day, the tag collects similar data from the whales. The difference? Instead of the analysis happening instantly on the device, I process everything later on my computer. This technology has completely transformed how we study whale behavior, opening up new ways to understand their lives beneath the surface, and I believe it's only going to get more advanced.
What is your favourite animal, and why?
My favorite animal is the killer whale, which is a bit ironic, considering they prey on my study species, the humpback whale. I've always been fascinated by their intelligence and complex social interactions. There's something almost adorable about their black-and-white appearance, which is funny when you think about the fact that they are actually apex predators. That said, over time, I've also developed a deep attachment to humpback whales. Every new discovery I make about them only leads to more questions, strengthening my curiosity about their lives and evolution. The more I study them, the more I realize how much we still don't know, which, to me, is what makes them so captivating.
Maevatiana Ratsimbazafindranahaka's contact details: Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Bücklestraße 5a, 78467 Konstanz, Germany.
E-mail: [email protected]
