Creature Feature: Manta Rays and the Plankton Buffet

Manta Ray and the Plankton Buffet

If you’ve ever been stuck on the freeway when a rogue 18-wheeler suddenly appears in your rear-view mirror, you might know what it is like to be in the water with feeding Manta rays. Plankton buffet for them means no visibility to us, and it is virtually impossible to see where they are in the water. When you do spot one, they’re right on top of you, and nothing less than Mack trucks. But, if you happen to come across a Manta ray when you are diving in crystal clear waters, they won’t be feeding and they are absolutely awe-inspiring.

Most of us are aware that Mantas feed on plankton and not humans. Perfectly harmless. Harmless and large. Sort of like Hagrid from the movie Harry Potter. However, harmless and large is a little unnerving in planktonic murk when you can only see about an arms length in front of you. This is especially true when these overgrown-underwater-hangliders decide to do back-flips. Whoa-Nellie!

Whether sighted from above or below the water, Manta rays are awe inspiring and spectacular to witness. On the surface of calm waters it is the pectoral fins cutting through the surface that usually gives them away. Underwater, their form is a little more ominous as they approach from the distance. Whichever the first sighting, these rays are quite a sight to behold underwater. They take on the weightlessness of a bird, effortlessly cruising over a reef. While their sheer size and magnitude remind one of how powerful they are.

Manta rays are the largest of all the rays, reaching a wingspan of up to 20 feet and weight up to 4,000 pounds. They have a distinctive diamond body shape similar to cownose and eagle rays and belong to the family of devil rays. The pectoral fins of these rays are extended, and they have two extra extensions known as cephalic lobes. These lobes continue towards the mouth from the outer large wings and are usually coiled close to the body. Another interesting characteristic of these rays is their relatively short tail and lack of stinging spines.

Mantas have a classic countershaded coloration to their bodies, dark on top and light on bottom. Despite their enormous size, these rays blend in quite well with the surrounding water.

Manta rays feed during daylight hours, as well as during the night. The plankton that manta rays feed upon have a tendency to concentrate under lights of dive boats at night. From the perspective of a Manta ray, this is hardly an opportunity to pass up. This is where many divers will often see these rays, performing their nighttime ballet in the stage lights of dive boats. Mantas will swim with their giant mouths open extremely wide and their cephalic lobes unfurled to direct the stream of plankton into their mouths. Not only do the back flips assist the rays in efficiency, but also as a method for concentrating the plankton into even smaller clusters.