Rob’s Manta Ray Research with Barefoot Conservation in Raja Ampat...
Rob’s Manta Research with Barefoot Conservation & Marine Mega Fauna
Hi, my name's Rob and I spent 4 months with Barefoot conservation whilst collecting data for my master's project on manta rays, from January-May 2014. It is no exaggeration to say that I had an absolutely fantastic time, and I was able to collect a lot of really interesting data on the reef mantas (Manta alfredi) in this part of Raja Ampat. Through photo-identification using the unique 'belly-spot' patterns that each individual proudly wears (and are usually cooperative enough to present to a willing cameraman), in my time with Barefoot we were able to increase the size of our manta database to around 250 individuals. These include around 100 of the globally rare black morph, which are if anything even cooler looking than the normal 'chevron' morph!
All the mantas we have identified have names, which are based on what we imagine their spots look like. For example check out 'Bunny' below, with her cute ears! This allows us to remember each individual more easily so that we know instantly who we are looking at when we meet them underwater! During my time with Barefoot we focused our dives mainly on two dive sites close to Arborek island, which are both used as cleaning stations by manta rays, called Manta Sandy, and Manta Ridge.
Over many dives with the same rays, you start to notice really interesting things that some of them do. Each individual has a different character and this is what makes mantas so fascinating to watch in my experience. Some of them charge in the middle of the action as soon as they arrive and clearly like to make their presence felt at the cleaning station, whilst other are content to hang around the edges. The older, more experienced rays tended to be the most camera-friendly, whereas younger rays tended to vary more in their behaviour, some being very playful and excitable, whilst others seemed more shy. We noticed some strange things as well, like one particular manta that always seemed to travel with a large shoal of tiny pilot fish around its mouth. Every time we saw her (5 times over a period of several weeks) the same group of fish were there with her.
Even after diving with them hundreds of times you can still be amazed when an individual does something you did not expect, and watching a large group and how the mantas react to each other is really a sight to behold. The style of diving at Manta Sandy, where you sit and watch whilst the rays swoop around you, and the fact that this is a well established dive site where rays are used to being in contact with humans- is very conducive to observing natural behaviours. This may be because the rays have become 'habituated' to human presence there, and feel comfortable performing their normal behaviours.
I am particularly interested in the social aspect of manta behaviour. Manta have the largest brain-body size ratio of any fish, which is likely to be linked to their apparent high levels of sociality. They are often found in groups performing different kinds of behaviours, such as cleaning and feeding. Behaviours such as breaching out of the water (which we have observed many times) and fin-slapping the water may be communicative, though very little is known about if and how mantas may communicate underwater. My thesis, and the work I will now continue on this hopes to answer some of the questions which remain about manta groups. For the moment I am focusing on the question of whether the groups of individuals which we see are groups which are acting as social groups, with individuals forming association with other individuals that are conserved over time. This requires identifying all the rays present in a particular group, and identifying patterns of association that may be present. We noticed that the two main sites we studied had very different groups of mantas which used them, with only a few mantas being seen at both sites, despite the sites being only a couple of kilometres apart. This suggests that mantas may have territories which particular social groups favor.
I have observed rays that were seen together several times over the course of a few months, and only rarely seen without the other. To me this suggest strongly that the mantas not only are aware of who they know, and their relationship with many other individuals, but that they are able in some way to communicate with these individuals and coordinate their movements, in the same way that as humans we organise to meet up with our own friends. I believe questions like this will prove valuable in studying the movement dynamics of whole populations of manta rays, of which knowledge is critical if we are to protect populations from the impact of fisheries, which currently operate at completely unsustainable levels in many parts of the world.
Thankfully the mantas in Raja Ampat are well protected, and appear to be thriving. I am delighted to say that I will return to continue working with Barefoot and the manta ray research programme in November!! I honestly can't wait!
Why not come join us and help with our Manta research!
All the best
Rob