Long-life remote underwater video reveals dawn cleaning station use in the rare stingray, Megatrygon microps
Three years of remote underwater video in Tofo, Mozambique, revealed that the rare smalleye stingray (*Megatrygon microps*) utilizes a cleaning station primarily at dawn, with peak activity occurring before recreational divers arrive, thereby establishing this site as a predictable and ecologically significant habitat for the species.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Deep within the coral reefs of the world, there exist specialized meeting places known as cleaning stations. Here, small fish and invertebrates act as caretakers, removing parasites and dead tissue from much larger marine animals. This symbiotic relationship is a cornerstone of reef health, allowing massive creatures like sharks, turtles, and rays to maintain their hygiene without leaving their habitat. While scientists have long observed how manta rays and other large visitors use these stations, one of the ocean's most elusive giants has remained a mystery. The smalleye stingray, a rare and poorly understood species with a disc wider than a person is tall, is listed as "Data Deficient" by conservationists, meaning there is not enough information to know if it is safe or in danger. Understanding how this rare ray behaves, where it goes, and when it needs help is crucial for its survival, yet its secretive nature has made direct observation nearly impossible for researchers.
To solve this puzzle, a team of scientists turned to a method that requires patience rather than intrusion. Instead of chasing the animals or placing bait to attract them, they set up long-lasting, unattended cameras on the seafloor at a rocky reef in Tofo, Mozambique. Over a period of three years, these cameras recorded more than 519 hours of video, capturing the daily life of the reef without human interference. The researchers were looking for the smalleye stingray, Megatrygon microps, to see if it used the cleaning stations, how often it visited, and what it did while there. By reviewing thousands of hours of footage, they were able to count individual rays based on their unique spot patterns and scars, distinguishing them from one another even when they appeared on different days.
The cameras revealed a striking pattern in the ray's daily routine. The smalleye stingray does not visit the cleaning station at random times throughout the day. Instead, its arrivals are tightly clustered around dawn. In the hour just after sunrise, the rate at which these rays arrived was nearly nine times higher than at any other time of day. In fact, 43 percent of all the individual rays seen during the study made their first appearance between 6:00 and 7:00 in the morning. This specific window represents only a tiny fraction of the total recording time, yet it accounts for almost half of all the visits. The data suggests that this behavior is tied to the light of day rather than a fixed clock time, as the rays arrived within an hour of sunrise regardless of the season.
Once at the station, the rays engaged in very specific activities. The vast majority of the time, they were there to be cleaned. The footage showed them hovering in the water while small cleaner fish swam over their bodies, removing parasites. This cleaning behavior was the dominant activity, accounting for nearly 72 percent of the observed visits. The rays did not stay for long; most visits lasted only a minute or two, though some individuals remained for over an hour. Interestingly, the length of the visit did not depend on whether the ray was injured or how many "hitchhiker" fish, such as cobia, were swimming alongside it. The only factor that clearly changed how long a ray stayed was whether it was actually being cleaned or simply swimming through the area; those being cleaned stayed six times longer than those just passing by.
The study also examined whether the presence of other large animals or human divers affected the stingrays. The researchers found that the smalleye stingray and the more common manta rays, as well as SCUBA divers, used the same cleaning station but at completely different times. The stingrays arrived in the early morning, while divers and manta rays typically appeared much later in the day. Because their schedules did not overlap, the stingrays were never seen interacting with divers or being displaced by them. In one specific instance recorded on camera, a diver adjusted the equipment while two rays were cleaning, and the rays continued their activity without leaving. However, when a group of divers approached closely to take photographs later that same morning, the rays stopped cleaning and did not return for the rest of the recording session. This single event hints that the rays might be sensitive to close human contact, but the overall data shows that their peak activity time currently keeps them safe from routine recreational diving.
By identifying this predictable dawn window and confirming that the reef serves as a reliable habitat for dozens of individual stingrays, the study provides a vital piece of the puzzle for conservation. The smalleye stingray is a rare creature seen in very few places around the world, and knowing that this specific reef in Mozambique is a key location for its survival is a significant discovery. The research demonstrates that protecting the physical structure of the reef benefits the stingrays, the manta rays, and the tiny cleaner fish all at once. Since the stingrays use the site at a time when most divers are not yet present, current tourism practices do not appear to be harming them, but the findings also suggest that keeping human activity away from the station during those early morning hours would be a prudent way to ensure these rare animals can continue to use this essential resource.
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