In the open ocean, a manta ray's path may seem deliberate until, without warning, it slips beneath the surface and disappears into the blue. After a few hours or days, it appears again far from where it started. Scientists have long wondered what is driving these declines. Now new evidence suggests that stingrays may not be diving to hunt, but to find a way across the open sea.
More than ten years marine biologists tracked down dozens of manta rays to understand their deep descents. They found that the animals occasionally plunged into darkness for several hours, surfacing hundreds of kilometers to the surface. These dives often coincided with periods of long-distance movements, hinting that manta rays may use depth to reorient themselves before continuing their journey.
“We show that offshore, oceanic manta rays are capable of diving to depths of more than 1,200 meters. [almost 4,000 feet]“This is much deeper than previously thought,” said first author Calvin Beal in press release. “These dives, which are subsequently associated with increased horizontal movement, may play an important role in helping mantas gather information about their environment and navigate the open ocean.”
How manta rays use the ocean depths
The deeper a manta ray dives, the more stable its environment becomes. Deep below the surface, changes in temperature, oxygen and light smooth out into stable gradients that can serve as subtle markers. Beal and his colleagues believe that manta rays may use these layers to sense environmental cues, perhaps magnetic or chemical changes, that help them navigate the open ocean.
“Understanding the nature and function of deep dives helps explain how animals traverse vast, seemingly featureless oceans and connect ecosystems thousands of kilometers apart,” Beal said.
Not all manta rays behave the same. Those who traveled through deeper sea waters were much more likely to dive, while people who remained near shallow coastal areas rarely descended below 1,600 feet (500 meters). In areas where the seafloor drops sharply into deeper water, manta rays dive most frequently, suggesting that topography and depth influence when and why they dive.
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Hidden patterns of manta diving
From 2012 to 2022, researchers attached small satellite tags to 24 oceanic manta rays off the coasts of Indonesia, Peru and New Zealand. The devices recorded depth, temperature and movement, then detached after a few months and floated to the surface, where the team could recover them and download the data. Finding the tags was not easy; Scientists often had to scour large areas of the ocean to find a small gray antenna bobbing among the waves.
In the end, the team recovered eight tags, producing the first high-resolution recording of manta diving behavior. Together, they collected more than 2,700 days of data, tracking thousands of dives and finding that the rays sometimes plunged to depths of about 4,100 feet (1,250 meters), where temperatures hovered around 41 degrees Fahrenheit (5 degrees Celsius).
The dive profiles followed a clear pattern: long pauses at the surface, steep descents interspersed with short “steps”, and slow climbs back to the light. These dives were rare—less than three percent of all recorded activity—but often preceded bursts of horizontal travel spanning hundreds of kilometers, suggesting a link between deep diving and long-distance navigation.
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Ocean Health and Conservation
The results help explain how diverse marine species connect distant habitats, from coastal reefs to the open sea. By diving into deeper, colder layers, manta rays may be testing their sense of place in a vast and changing ocean.
“Our study highlights how dependent migratory species are on both coastal and riparian habitats, highlighting the need for international cooperation in their conservation,” Beal concluded. “It also reminds us that the deep ocean, which regulates Earth's climate and supports global fisheries, remains poorly understood but vitally important.”
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