A new multi-sensor tag reveals how eagle rays crush prey underwater, capturing synchronized motion, sound, and video data to decode their elusive feeding tactics in fine detail.
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A team of researchers has developed a compact, high-resolution biologging system designed to study the shell-crushing feeding strategies of durophagous rays. The breakthrough, published in Animal Biotelemetry, combines several different sensors (accelerometers, gyroscopes, hydrophones, video cameras, and acoustic transmitters) into a single, robust package that can be temporarily attached to rays in the wild.
This multi-sensor approach enables the capture of subtle, high-frequency motion patterns alongside real-time sound and visual recordings. It offers the clearest picture yet of how these animals feed and move in their natural environments.
Limitations of Previous Tagging Methods
Most studies of benthopelagic rays have relied on direct observation or short-term tagging with single-sensor devices. These techniques often lack the resolution needed to detect rapid, complex behaviors like prey capture or feeding strikes. Conventional tags also suffered from short retention times and insufficient data synchronization across different sensing modalities.
Morphological features of rays, such as their flattened bodies and delicate skin, make secure attachment difficult. Foraging events involving shell crushing require an abundance of data—motion data, audio, and visual confirmation—making capturing the full context of feeding behavior extremely challenging with previous tools.
Designing a Smarter, More Durable Tag
The new biologging system includes a triaxial inertial measurement unit (IMU) that records accelerations and angular velocities at 50 Hz, allowing researchers to pick up fine-scale changes in posture and dynamic motion. Further detail is captured with a broadband hydrophone that records audio signals from zero to 22,050 Hz, picking up key acoustic cues such as shell fractures or handling sounds during prey capture; a miniature video camera captures footage of the animal’s behaviour in situ.
An acoustic transmitter was integrated and synchronized with the rest of the system to allow remote tracking and data retrieval. All components are housed in waterproof, pressure-resistant casings, and the full unit measures roughly 24.1 x 7.6 x 5.1 cm, weighing 430 grams in air.
A More Secure Fit for Longer Studies
The tag is attached to the rays using silicone suction cups reinforced with custom straps that loop around the spiracle cartilage. This method dramatically improves tag retention time over previous methods. A galvanic release mechanism detaches the tag after either 24 or 48 hours, ensuring the animal’s welfare post-deployment.
The system was tested in the lab and the field, using white-spotted eagle rays. Researchers tested sensor performance in captivity, assessing tag stability and retention duration. These trials were followed in the wild to record natural behaviors, focusing on feeding behavior.
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Distinct Feeding Signatures Revealed
The high-frequency IMU data uncovered distinct kinematic patterns during foraging, including pronounced pitching and dynamic surge motions linked to shell-crushing behaviour. These signatures helped distinguish feeding events from other actions like browsing or digging.
Acoustic recordings captured sounds of prey handling, including shell fracture events that aligned with the motion data. This multimodal integration proved particularly useful when visibility was low or direct observation was not possible.
The video footage offered visual confirmation, helping to validate interpretations from the sensor streams. While recording time was limited by battery constraints, the data highlighted the potential for extended deployments with future power-saving improvements.
A Platform for Automated Behaviour Analysis
The tag’s integrated design enhances the accuracy of behaviour monitoring and sets the stage for developing automated classification systems. With synchronized motion, sound, and visual data, researchers can begin training models to identify specific behaviours without needing constant human review.
Importantly, the spiracle-based attachment approach extended tag retention to nearly 48 hours in some cases, well beyond the sub-24-hour durations typical of earlier designs.
Journal Reference
Hampton C.M., et al. (2025). Sticking with it: a multi-sensor tag to reveal the foraging ecology and fine-scale behavior of elusive durophagous stingrays. Animal Biotelemetry 13, 23. DOI: 10.1186/s40317-025-00416-2, https://animalbiotelemetry.biomedcentral.com/articles/10.1186/s40317-025-00416-2