MANTA RAYS

manta-rays
Giant Pacific Manta Rays

 

The Giant Pacific Manta Rays (Manta birostris) are the largest species of all the rays. The largest known specimen was more than 7.6 meters (25 ft) across, with a weight of about 1,300 kilograms (2,900 lb).

Those of us who have been lucky enough to encounter one of the curious Giant Mantas can’t help but feel there is an intelligence there, scientists tell us Mantas have the largest brain-to-body ratio of the sharks, rays and skates. You see this in their curiosity about humans and their willingness to interact with us . . .

MORE ON GIANT PACIFIC MANTA RAYS

The giant oceanic manta ray can grow to a disc size of up to 9 m (30 ft) with a weight of about 1,350 kg (2,980 lb). It can live for 20 years. It is dorsoventrally flattened and has large, triangular pectoral fins on either side of the disc. At the front, it has a pair of cephalic fins which are forward extensions of the pectoral fins. These can be rolled up in a spiral or can be flared out to channel water into the large, forward-pointing, rectangular mouth when the animal is feeding. The teeth are in a band of 18 rows and are restricted to the central part of the lower jaw. The eyes are on the side of the head behind the cephalic fins, and the gill slits are on the ventral (under) surface. It has a small dorsal fin and the tail is long and whip-like. The manta ray does not have a spiny tail as do the closely related devil rays (Mobula spp.). The skin is smooth with a scattering of conical and ridge-shaped tubercles.  The colouring of the dorsal (upper) surface is black, dark brown, or steely blue, sometimes with a few pale spots and usually with a pale edge. The ventral surface is white, sometimes with dark spots and blotches. The markings can often be used to recognize individual fish

When travelling in deep water, the giant oceanic manta ray swims steadily in a straight line, while further inshore it usually basks or swims idly around. Mantas may travel alone or in groups of up to 50 and sometimes associate with other fish species, as well as sea birds and marine mammals. They are filter feeders and consume large quantities of zooplankton in the form of shrimp, krill, and planktonic crabs. An individual manta may eat about 13% of its body weight each week. When foraging, it usually swims slowly around its prey, herding the planktonic creatures into a tight group before speeding through the bunched-up organisms with its mouth open wide.  While feeding, the cephalic fins are spread to channel the prey into its mouth and the small particles are sifted from the water by the tissue between the gill arches. As many as 50 individual fish may gather at a single, plankton-rich feeding site.

giant pacific manta ray
Cleaning Station
The giant oceanic manta ray sometimes visits a cleaning station on a coral reef, where it adopts a near-stationary position for several minutes while cleaner fish consume bits of loose skin and external parasites. Such visits occur most frequently at high tide.  It does not rest on the seabed as do many flat fish, as it needs to swim continuously to channel water over its gills for respiration.

 

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