Researchers have unveiled remarkable insights into the behavior of oceanic manta rays, the world’s largest species of ray, during a significant study spanning a decade. Researchers used satellite tags to track the movements of 24 manta rays across three different regions — Raja Ampat in eastern Indonesia, Tumbes off of the northern coast of Peru, and Whangaroa in northern New Zealand. Their discovery uncovered that these mammoth creatures dive to phenomenal depths, possibly to develop cognitive maps of the massive oceans they occupy.
This high seas migration was the first study to track oceanic manta rays diving to depths of 1,250 meters on 79 individual dive records. Most remarkably, 71 of these extreme dives were in the waters off New Zealand. Such behavior is suggestive of the rays undertaking some deep dives. Besides the stunning imagery and beautiful bioluminescence, they’re probably using these dives to gather critical navigational and hydrographic data in complex seafloor areas.
Tagging and Data Collection
From 2012 to 2022, scientists observed intense tracking of oceanic manta rays, accumulating 2,705 tag-days of data. They were able to successfully tag some of these rays with satellite tracking devices that recorded data at high frequency intervals (every 15 seconds). The results show a surprising diving pattern to the rays’ behavior. In New Zealand, the rays started some of the steepest dives.
In New Zealand, common oceanic manta rays make deep dives immediately after departing the continental shelf. They typically begin these remarkable dives within 24 hours of moving into deeper waters. This behavior further reinforces the belief that they are probing deep, offshore habitats. Here, rapid changes in the seafloor’s topography occur on a minute to minute basis.
To track the sharks’ movements, the study used eight of these tags, which were set to release several months later and were then recovered upon surfacing. Sixteen of these unrecovered tags sent summary data back through the satellite. This gave researchers a unique, near-real time view of the rays’ movements and behaviors.
Diving Behavior and Environmental Cues
Oceanic manta rays’ complex dive behaviors suggest a high level of environmental awareness. After these extreme dives, researchers found that these rays were highly mobile. The next few days they continued marching – often more than 200 kilometers in a day. This unexpectedly complex movement pattern leads to the conclusion that the rays might be dynamically mapping their surroundings. They accomplish this while swimming across vast, open, deep-water expanses.
Manta rays float into regions with steep declines in ocean floor depth. This behavior allows them to better benefit from special ecological indicators. Scientists believe that they can rely on changes in magnetic field strength and gradient to cross the unbroken expanse of the ocean. They look at changes in oxygen levels, temperature gradients, and light levels as key navigational markers in their migration.
In Raja Ampat, the waters are generally shallow, and deep-water corridors are hard to come by. Consequently, oceanic manta rays exert less evolutionary pressure to search for navigational cues. The comparatively short distances between those deep valleys and busy surface streets makes for easier dives. This makes for less dramatic dives, particularly compared to what has been documented from the coast of New Zealand.
Implications of the Findings
The findings from this study shed light on the behavioral ecology of oceanic manta rays and their adaptations to diverse marine environments. Figuring out how these rays pretty much go all over the wide open ocean is key to protecting them. As they face threats from fishing practices and climate change, insights into their behaviors can inform protective measures and management strategies.
The study highlights the remarkable feats oceanic manta rays are capable of. It highlights the necessity for long-term research to know their movements and ecological roles in marine ecosystems. Collectively, scientists are racing against the clock to untangle the myriad threats to these majestic creatures’ lives. They highlight the need to work together to save their homes.