Gliding effortlessly in the tropical waters of the Philippines and other parts of the world, the giant manta ray or oceanic manta ray (Mobula birostris) is quite an underwater sight. With a wingspan of up to 29 ft (8.8 m) and weighing up to 5,300 lb (2,404 kg), it is one of the largest known living fishes, and the biggest among the rays. It also has the largest brain of any fish studied so far—and even exhibits signs of possible self-awareness.
Like the blue whale, this massive fish is a filter-feeder. It swims open-mouthed, using the gill plates in its mouth to filter krill and plankton. It possesses a pair of cephalic lobes, fleshy projections which help it draw more water and food into its mouth. While not much is known about the giant manta ray’s developmental stages, we’re aware of some specimens reaching up to 40 years of age. It’s said that giant manta rays only give birth to a single pup every two to three years.
Of course, a big brain isn’t automatically a sign of high intelligence. However, the parts of giant manta rays’ brains associated with intelligence, vision and motor coordination appear to be enlarged. These otherwise solitary animals have also demonstrated signs of social intelligence, as they’ve been observed to hunt in coordinated numbers. Additionally, they’re among the few species capable of passing the mirror test, which researchers conduct to measure self-awareness in animals. (Experts aren’t entirely convinced that it’s an accurate gauge of animal self-awareness, though.)
Due to their large size, giant manta rays have very few natural predators. Unfortunately, the most critical threats to their existence tend to come from human hands: commercial and illegal fishing, oil spills, plastic pollution, unregulated tourism, the destruction of their natural habitats, and even passing ships and boats.
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