Often when people think of sharks, they think of it swimming, effortlessly slicing through the ocean’s blue waters. But I want to challenge you to rethink that image of a shark and instead of swimming, picture one that seems to walk, using its fins to clamber across the seafloor in search of food.
This is the Raja Ampat epaulette shark, Hemiscyllium freycineti, a small species found nowhere else on Earth except the waters surrounding Indonesia’s Raja Ampat Archipelago. Despite living in one of the most celebrated marine biodiversity hotspots on the planet, surprisingly little has been known about how these sharks live, grow, move, and use their habitat. But a new study is now helping to change that, providing the first comprehensive look at the biology and ecology of one of the world’s most unique sharks.
Over 14 months, researchers conducted 64 nighttime surveys across six locations in Raja Ampat’s Dampier Strait region. Armed with headlamps and flashlights, they searched shallow reef flats, seagrass meadows, mangroves, and sandy habitats during low tide. The effort produced an impressive dataset: 1,191 shark sightings representing 736 unique individuals. One of the most striking findings was just how many sharks were present with relative population densities ranging from 333 to 2,462 individuals per square kilometer (some of the highest densities ever recorded for any species within the walking shark genus Hemiscyllium). In certain locations, particularly around Arborek Island and Sawinggrai, the sharks appeared remarkably common.
While those sort of numbers may sound reassuring for a species currently listed as Near Threatened, but these sharks occupy an extremely limited geographic range and unlike many larger shark species that can travel hundreds or even thousands of kilometers, Raja Ampat epaulette sharks appear to be “homebodies” in the most literal sense of the term. Researchers re-encountered 256 individuals during the study, some over a year after they were first recorded! And not a single shark was observed moving between study sites. Even within sites, movement distances were surprisingly small with the greatest net displacement recorded being only 475 meters. Most individuals spent their lives within much smaller areas than this.
This strong of site fidelity creates an interesting conservation paradox because on one hand, if local habitats remain healthy, sharks may thrive. On the other hand, if those habitats are damaged… well, the sharks have few options. Very few options. So what happens when a species rarely ventures far from home in a world where coastal environments are changing rapidly?
The team not only looked at movement in the sense of numbers but how these sharks use their habitat throughout life. Although most sightings occurred in seagrass meadows, the age structure of the population told a more nuanced story with coral reef habitats containing a disproportionately high number of juvenile sharks (nearly 70 percent of individuals observed there classified as immature). In contrast, seagrass beds and sandy areas contained larger proportions of adults. This suggests a form of “ontogenetic habitat partitioning,” or how animals use different habitats at different life stages. For Raja Ampat epaulette sharks, coral reefs appear to function as nurseries where young sharks can grow under the protection of complex reef structures before moving into more open habitats as adults. This sort of pattern mirrors what scientists have observed in many larger shark species, showing that even small sharks depend on networks of interconnected habitats. Protecting adults alone, afterall, is not enough if juvenile habitats disappear.
The researchers also gathered valuable information about growth and reproduction. Females slightly outnumbered males, producing a significantly female-biased population. Individuals ranged from just under 8 to 29.5 inches (20 centimeters to 75 centimeters) in length, with males and females reaching maturity at almost exactly the same size, around 22 inches (56.5 cm). Young sharks grew much faster than adults, averaging nearly 3 in (8 cm) per year compared to less than 1.2 in (3 cm) annually in mature individuals. Growth patterns also showed strong seasonal fluctuations, likely reflecting changes in environmental conditions associated with Raja Ampat’s monsoon-driven oceanography.
These life-history traits suggest that this species grows relatively quickly and reaches maturity early compared to many larger shark species, which at first glance seems like a recipe for resilience. But the Raja Ampat epaulette shark evolved less than two million years ago and exists only within a narrow slice of the Indonesian archipelago. Its dependence on shallow coastal habitats means it faces threats from tourism development, habitat degradation, pollution, and climate change. While the species received full legal protection in Indonesia in 2023, legal protection is only as effective as the knowledge that guides conservation decisions. Which is why baseline studies like this one matter so much because it is difficult to protect a species when basic questions remain unanswered.
How many individuals exist?
Where do they spend their time?
Which habitats are essential for reproduction and survival?
How far do they move?
Until now, scientists had only fragments of those answers for Hemiscyllium freycineti. And its future depends on whether the shallow seagrass beds, coral reefs, and mangrove-fringed coastlines it calls home remain intact. While this study offers reason for optimism — the sharks are still there in remarkable numbers — but the world is a dangerous place for an animal whose home is measured not in oceans, but in meters.