This Week in Zoology: Manta Rays


Another video is circling in my feed, and so another inspiration for a This Week in Zoology was born. Like the last one, this one is also beautiful to watch. Also like the last one, it seems to be sparking a question: what are those silly rays doing?

 

Those are manta rays, seemingly doing a series of belly flops. And no, that’s not because they lose all grace and coordination in the air, they are actually belly flopping on purpose.

 

First things first, manta rays are massive. Given the lack of any other object in the video that one could use for scale this is not immediately obvious in the video. So, here’s a picture of a manta ray swimming alongside a person

Manta-Ray2_682_1050268a

You get the idea. (source)

 

Rays are, essentially, flat sharks. Both are in the class Chondrichthyes, which means that they do not have bones, but rather their skeletons are made of cartilage. Manta rays are not aggressive, they do not have stings, but are simply content to slowly swim around, filter feeding in the water, and occasionally jumping out and doing a belly flop, a behavior known as “flying”.

So, why do they do this?

Because floating along in the ocean can get dirty. Dead skin, parasites, and other nasty business will tend to accumulate on your body. Therefore, the rays will jump into the air as high as they can and then smack into the surface of the water, to dislodge all the unwanted stuff.

Essentially, that video caught the rays during their exfoliation routine.

Manta rays are not the only rays that do this. A few years ago, a woman in Florida was killed by a 75-pound eagle ray. Having happened relatively soon after Steve Irwin’s death, there was a general panic about it: oh noes, are rays now on the list of super dangerous creatures that we need to fear?

Alas, no. The woman in question was sunbathing on a boat, and the ray jumped out of the water, hoping to belly flop and exfoliate, and instead it belly flopped right on top of the human that happened to be in its way. They both died in the process. It was an incredible coincidence and just a case of very, very bad luck.

So, don’t be afraid of rays just because they happen to share a class with sharks! As a matter of fact, you shouldn’t really be afraid of sharks either, but that will be for another Week in Zoology.

Comments

  1. Kreator says

    You know, I’ve actually wondered many times if rays or flying fish could eventually evolve into full-fledged airborne fish. I guess it could be possible, but competition from birds certainly is a huge obstacle. The fact that, as far as we know, fish never took that evolutionary path before also makes me think that there could be, in fact, insurmountable barriers for that to happen.

    • thoughtsofcrys says

      What do you mean by full-fledged airborne fish? Like, that they would never have to return to the water to breathe? There are definite evolutionary obstacles there. Or, as an intermediate animal that can both swim in the ocean and fly in the air? There is the problem that the bodily structures which make for good swimming and bodily structures which make for good flying are at odds. As for evolution not having taken that step, you also have to think of the potential benefit, and not only the obstacles. What evolutionary benefit would there be to evolving into airborne fish? Without a benefit to the species, natural selection cannot favor it.

  2. Kreator says

    I was thinking of fish capable of powered flight, as opposed to simply gliding like our modern flying fish; being able to breathe air was a possibility in my speculations but not necessary. I hadn’t thinked about the need of specific advantages though – that’s why you’re the scientist!

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