So as promised, let's get some clarity on what a mobula ray is shall we? The Mobulids are a family of rays that contain the two species of Manta Ray and nine species of Mobula Ray. So most simply mantas and mobulas are cousins. I mean phylogenetically of course, not in a first cousin Claire that we only see once a year at Christmas kind of a way. Manta and Mobula are the names of the two genus’ in the family Mobulidae and they are very similar to each other indeed. The main differentiating feature is their size with adult mantas generally much larger but the shape of their mouths and their cephalic (that’s a fancy word for head) fins differs between the genus’ too.
The photo above shows just one of the nine Mobula Ray species (which are commonly known as Devil Rays hence the hilarious title of this post) and like mantas, they too are beautiful animals.
As nice as mobulas are (and we hope to see a few of them whilst we are out here!) the two species of manta ray are the reason we’re in Bora Bora. One is called the Reef Manta (Manta alfredi) and the other the Oceanic Manta (Manta birostris). As Bex mentioned last time out they are both magnificent beasts and a large Oceanic Manta can get to over 7m across! They’re quite tricky to tell apart as although the Oceanics get much larger it is of course possible to encounter juvenile and sub adults which confuses things slightly. The easiest way is to look at them from above and see what shape the black markings on their heads are. The Oceanic Manta has a T-shaped shoulder stripe and the Reef Manta has a Y-shaped marking in a similar position. For more info on how to tell them apart visit the Spot the Difference page on the Manta Trust website.
The photos below show a Reef Manta (left hand side with Y-shaped black patch) and an Oceanic Manta (right hand side with T-shaped black patch) next to each other. Hopefully you can see the difference in their patterns?
The two species have quite different habits with the Reef Manta (as the name suggests) associating with small groups of islands or reefs in shallow waters. They tend to be highly social sticking to a specific home range whilst following seasonal changes in food availability. We call this a resident species and it is sometimes known as the Resident Reef Manta. The Oceanic Manta is in contrast a more open water species spending the majority of its time feeding out in the big blue! It comes in to reefs to visit cleaning stations or at particular times of year for plentiful feeding. (By the way, a cleaning station is like an underwater carwash for rays, fish, sharks, turtles etc. where they get little parasites or dead skin removed by a crew of specialised cleaner shrimp and fish. These are awesome and I’m sure we’ll post more on this later!). It is during these times, when the oceanics are more coastal, that if we are lucky enough we get a chance to dive with them.
There are very few places in the world where one can hope to see both species in one place and French Polynesia is one of those places. Whether we do see both species together and, if we do, how they interact with each other is one of the reasons we are here. Studying this is just one exciting aspect of the research we hope to carry out through observing them over the next 6 months. More details on our project and what we hope to achieve in the coming posts.
Thanks for reading!