Creature Feature – Get to Know the Manta Ray

Dreaming of diving with the charismatic Manta Ray – watching them glide majestically above you, wondering at their grace and beauty?  Want to learn more about them?  Here Sze Wei shares some of her favourite facts about them!

Manta rays are definitely one of my favourite marine friends, and seeing one in a dive always makes my day.  I love that they are often curious enough to come investigate and interact with well behaved divers. I’ve been fortunate enough to have playful encounters with mantas all around the world, including two citizen science expeditions with the incredible Dr Bob Rubin from the Pacific Manta Research Group.  And while I’m not a manta expert or a manta scientist (just a manta aficionado), I thought of sharing some of the incredible and interesting things I’ve learnt about my favourite flappy ocean dweller.

Flattened Sharks

Dr Bob Rubin likes to tell us that rays are essentially flattened sharks.  And along with a mental image of trying to get a great white into a waffle iron, my first reaction was “Really?  But they’re so different!”. And from a shape perspective, they certainly appear to be. However biologically and evolutionarily, they are very closely related – and when you start thinking of slightly flatter shark species such as guitar sharks and saw sharks, it starts to make more sense.  So manta rays are highly specialised flattened sharks!

Mobula Rays in Baja California Sur, Mexico
Diving with manta rays in mexico

The Two Species

It’s generally accepted that there are two species of manta rays that are frequently encountered by divers – the reef manta (Manta alfredi), and the oceanic manta (Manta birostris).  So, if you’re lucky enough to see a manta in a dive, how can you tell which of the two species it belongs to?

Well size is the first distinguishing feature – with reef mantas being smaller, reaching up to 5.5m (18 ft), and oceanic mantas 7m (23 ft).  But this is not really a reliable measure, as demonstrated by a recent dive trip to the Maldives, where there reef mantas were huge and easily on par with the size of oceanics in Socorro!  So how else can we tell the difference?

I’ve learnt that the best to tell is by their markings.  So if you’re above the manta, looking at the dorsal side, or top of the manta – if the shoulder markings form a sharp well defined T, it’s probably an oceanic manta.  If the shoulder markings are less well defined, it’s probably a reef manta.

Now, if you’re below the manta, looking up at the ventral, or belly side, oceanic mantas will usually have a clear dark V shape along the pectoral fins, which won’t be there on a reef manta.

Speedy!

Ever tried to keep up with a manta?  You know, there’s always those over excited divers who try to extend their encounters by swimming after a disappearing manta – burning up their air, they get tired soon enough!

So how fast do mantas swim?  Pretty fast, as it turns out, at 9 miles an hour.  And they’re capable of bursts of up to 22 miles an hour.  To put it in perspective, Michael Phelps’s fastest swim is at 6 miles an hour – so nope, you’re not going to catch up with that manta going off in the distance!

How does this compare to their cousins, the sharks?  Well a mako, the fastest shark in the world, is capable of speeds up to 60 miles an hour, and a great white at 25 miles per hour.  So our flappy friends are slightly slower than their streamlined relatives.

snorkeling with manta rays in mexico
Diving with manta rays in Baja California Sur, Mexico

Technicolour or Monochrome World?

My dive buddy Valerie and I once cornered Dr Bob while we were on a Citizen Science trip to find out if mantas can see in colour.  The backstory here was that we wanted to know if mantas can appreciate Val’s awesome purple manicure while she was waving hello at them!  From such humble beginnings are awesome insights uncovered!

And the answer from Dr Bob is… that they don’t know!!  It just goes to show how little is known of manta rays and how so much research there is still to do.  Speculating, Dr Bob says that possibly they see in black and white. Animals who are colourful tend to be able to perceive colour, and as mantas definitely are on the monochrome scale, this may indicate that that they don’t see colour.  Also, mantas are closely related to sharks (where there has been a lot more research), and sharks in general are not able to perceive colour.

What’s Manta Skin Like?

Mantas look incredibly and smoothly graceful – you’d think that they have soft pretty skin to go with that.  And… they don’t! If you’ve ever had a shark brush against you, then you’ll be familiar with the sandpaper feel of their skin – and mantas, their close cousins, are exactly the same!  A manta’s skin is covered by “dermal denticals”, which are small tooth like structures. These structures help remove turbulence and drag in the water (swimsuit manufacturers are apparently studying this to try and replicate this in their products).  These little teeth are then covered by a protective mucus coating, which helps prevent infection. Unfortunately is coating is easily lost on contact with humans, so no matter how friendly the manta appears, please avoid touching them.

Scuba diving with reef manta rays in the Maldives
Reef mantas circle a cleaning station in the Maldives