Whale sharks (Rhincodon typus)—the world's biggest fish—are one of the most charismatic marine species. They connect with the hearts of anyone lucky enough to encounter them, making people deeply curious about their lives and invested in their conservation.
Yet most of what researchers know about the behavior of whale sharks comes from snorkeling or watching them from boats at the sea surface—only a small part of their entire habitat. Much of their lives below the surface remains a mystery.
Whale sharks live in tropical oceans where food is often sparse and patchily distributed, so they need to constantly adapt. As oceans are affected by climate change, food for whale sharks may become even scarcer, so it's important to understand their feeding strategies.
The new research, published in Marine Biology, used cameras carried by whale sharks to follow them below the water surface in a tropical coastal gathering site.
Our work has revealed new behaviors and, for the first time, provides a more comprehensive picture of whale shark foraging strategies throughout the water column—from the surface to the bottom of the sea.
Going where we can't follow
Before our study, researchers mainly described whale shark behaviors by watching them in person at the ocean surface.
This provided only a snapshot of whale sharks' full lives, and observations often ended prematurely when the fish decided to dive deep. For example, one description of a possible mating attempt was cut short because the whale sharks dove out of sight of our research team.
A common method scientists use to investigate animal behavior in the wild is attaching electronic tags. These small trackers provide data on movements beyond where we can see them. For marine species, that includes both farther from the coast and while diving below the surface.
Although data from tags are incredibly valuable for understanding movement patterns, we can't infer specific behaviors from these data—because we still can't see the animals.
What do they do when nobody's watching?
Through our new study, we could finally address the question: "What do whale sharks do when no one is watching?" Filling these research gaps is essential so we can help protect these majestic yet endangered filter-feeding animals.
We used tags that collect high-resolution movement data and have a small camera. The camera provided footage of the front half of the shark, as well as a view from the shark's perspective. It's as close as we can get to seeing the ocean through their eyes.
With these cameras, we could see what the shark was doing while the tag was also collecting data on its movements. We attached our tag to the dorsal (top) fin while snorkeling alongside the shark. Unbothered, these gentle giants continued to swim while we watched them disappear into the open blue water.
After a preset 24-hour period, the clamp and camera tag fell off, leaving nothing on the animal and allowing us to retrieve the data without impacting the whale shark.
Using our video data alongside a review of more than 100 scientific publications describing whale shark behavior, we built the largest catalog of whale shark behaviors to date, defining 36 distinct behaviors.
We discovered whale sharks use a mix of feeding behaviors throughout the water column and along the seafloor, at depths of up to 70 meters (230 feet) in our study site. Researchers previously thought whale sharks predominantly feed at the surface, but this finding challenges that assumption.
Low-effort snacking
The range of feeding behaviors spanned from effectively sinking to the seafloor with an open mouth (gliding slow feeding) to vigorously swimming after krill swarms—their preferred prey—at the surface (active surface feeding).
The whale sharks in our study spent most of their time performing six low-effort feeding behaviors. This suggests they often snack in water with low prey density until they come across a patch with higher prey density, such as a krill swarm. Then, their behavior changes to active feeding. It's like snacking from the pantry while you decide what you're going to cook for dinner.
We also found that whale sharks have a much wider variety of foraging strategies compared with other filter-feeding megafauna, such as basking sharks and whales. This could help explain how they manage to thrive in tropical waters where prey is limited and patchy.
Our study captured behaviors from just one gathering of juvenile whale sharks at a coastal site near Ningaloo Reef, Western Australia. If researchers can attach more cameras to whale sharks at aggregation sites around the world, they will hopefully discover new insights and continue to expand our understanding of this iconic species.
Excitingly, we are beginning to understand the secret lives of the biggest fish on Earth, and from what we have seen, they are the ultimate snackers of the sea.
Publication details
Christine Barry et al, An ethogram for the whale shark (Rhincodon typus) with insights into foraging plasticity, Marine Biology (2026). DOI: 10.1007/s00227-026-04900-y
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