Giant Manta Rays Are More Predatory Than We Think

The manta rays that people thought only consume planktons near the ocean's surface are more predatory. The new research found.

Marine biologists have experienced difficulties in tracking down the diet of these majestic giant manta rays. The creature can grow up to 23 feet across and weighs up to 3,000 pounds. It is an endangered species and the specimens are quite hard to find.

A biologist from the Queensland University and study co-author Katherine Burgess said that "The previous knowledge of giant manta ray diet was based on observations of feeding activity on surface water zooplankton at well-known aggregation sites."

To further study the diet of these majestic giant creatures, Burgess and her team went to Isla de la Plata off the coast of Ecuador. The area is known for the presence of the giant manta rays. However, knowing that the giant manta rays are protected species, the researchers were not able to take a specimen. It is because the procedure can distress the manta rays and it is possible to be lethal. Thus, the researchers applied the "you are what you eat" principle to the problem, according to Gizmodo.

Burgess said that "We studied the giant manta rays' diet using biochemical tests, such as stable isotope analysis. From a muscle biopsy from a free-swimming animal." The test of which they have conducted can determine what the animals have been eating by examining a piece of tissue.

The result of the skin test showed that in the average diet of the giant manta rays, 27 percent of it came from the surface plankton. But, the 73 percent came from what the scientists call "mesopelagic" sources, which is a term for fish and other organisms that inhabit the areas of the deep sea that measures around 650 to 3,330 feet below the surface.

The researchers found that the giant manta rays are not the filter feeding gentle giants. In reality, they are a deep sea predator eating up small to medium size fish.

The new study is interesting. However, the researchers noted that actual observational evidence of rays feeding in the deep sea is needed. Thus, it worries them now as the deep ocean is the "next frontier for open fisheries." It will be a threat to the creatures that rely on the aquatic zone for food, according to IB Times.

 The study was published in the Journal Royal Society Open Science.