10th Sep 2013

Gentle Giants

Manta Rays are named by the Spanish word “manta”, meaning a cloak or blanket: a fitting word for the vast, pale, winged eagle rays. Because of their horn-shaped cephalic fins, Manta Rays are also known as “devilfish”, but the joke’s on whoever came up with that name, because despite their imposing appearance, Manta Rays are actually very gentle and social, and will let humans swim close to them without hurting them. They’re filter feeders, only eating zooplankton, and they don’t have venomous spines on their tails like stingrays—their only defence is their large, powerful wings. They’re the third biggest marine species behind sharks and whales, weighing up to 1,350 kg (3,000 lb), and we only recently realised there are two different species: M. birostris reaches up to 7 metres across, and M. alfredi reaches about 5.5 metres across. They’re found in tropical and subtropical waters, and while the bigger species migrates across the ocean, the smaller species sticks to coastlines. They’re ovoviviparous, which means that their pups are born rolled up like little tubes inside a thin shell, which then hatches inside the mother. We don’t know a whole lot about them, because they’re seldom seen and hard to keep in captivity because of their sheer size—in the Georgie Aquarium in Atlanta, four Mantas live in a tank that holds more than 22 million litres of water. They’re listed as a vulnerable species, with threats include the effects of pollution, being caught in fishing nets, and being harvested for their gill rakers, which are in high demand in Chinese markets because they’re thought to cure sicknesses from chickenpox and cancer. It’s a huge shame, because from what we do know about them, Mantas are fascinating and intelligent creatures, with the largest brain to body ratio of any living fish. Read more about their conservation.

(Image Credit: Violeta Jahnel / Andrea Marshall)

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