Manta rays have traditionally been considered as solitary animals who demonstrate very little social interaction and only aggregate together as part of their elaborate, but rarely observed, courtship & mating rituals or at special cleaning stations where they gather to be relieved of their parasites.
Spectacular but periodic aggregations also occur around seasonal concentrations of a rich food source – such as the coral spawning at Ningaloo Reef in Western Australia or the zooplankton storm near Isla Holbox off the northern tip of the Yucatan Peninsular in Mexico.
However a more recent school of thought is that manta rays are actually highly social animals and this sociability is why they have such highly developed intelligence and the largest known brain of any fish.
Either way a manta ray experience is on the “must-do” list of most divers & underwater photographers and what is special about Tofo is the sheer number of manta rays in the area – with about 750 individuals specifically identified and an estimated total population of around 1400, compared to an estimated 300 to 400 at other major aggregations.
Diving Mozambique: Why Tofo?
The Tofo area benefits from a quite extraordinary set of circumstances – firstly the southern Mozambique coastline has unique counter-cyclic eddies that produce a rich year-round source of zooplankton concentrated in a 200km stretch of coastline of which Tofo is the epicenter.
The availability of this reliable food source means that the area plays a very important role and field research by the Marine Mega Fauna Foundation has found that 75% of the identified mantas are female – indicating the area is probably a critical mating/breeding/birthing area.
Further research by the foundation has shown that the stretch of coastline is also an important migratory corridor for manta rays which has become a hunting ground for the diverse shark population in the area and the majority of the mantas have some form of shark bite injury.
The attacks appear to be random & opportunistic whereby the shark spots the manta and then attacks from behind, in the ray’s blind spot and manages a single bite before the startled manta accelerates away towards safety.
It’s almost (but not quite…) a win-win situation, because the shark is happy to have had a quick snack while the manta is presumably happy to have survived the attack and because all of it’s main organs are concentrated in it’s core, such attacks are rarely if ever fatal.
Investigation of the actual wounds has confirmed that while the majority of the injuries are the result of attacks by tiger & bull sharks, a total of 11 other sharks have also been positively identified as the predator.
Diving Mozambique: Tofo’s Manta Cleaning Stations
Large marine creatures inevitably suffer from significant numbers of tiny parasites that are extremely difficult for them to remove and while breaching is known to be a way of communicating, it is also thought to be a form of shock treatment used to shake them free.
But just as large reef fish & moray eels develop relationships with smaller fish & shrimp – allowing them to feed on their parasites under a temporary truce in the eternal cycle of hunt & eat – so do mantas frequent specific locations, called cleaning stations, where they will hover patiently while cleaner fish perform a similar routine.
Cleaning stations, such as the one at Gona Bara Bara island in Milne Bay, Papua New Guinea, are the perfect place to observe these magnificent creatures as they linger and allow the parasites to be removed, however it is unusual for individual mantas to remain around a cleaning station for much more than an hour.
But in the Tofo area it is quite normal for mantas to remain for several hours at a time because not only are their parasites being removed, their wounds are being cleaned of dead and infected flesh, thus allowing them to make a full recovery from their attacks.
Interestingly it has been observed that different types of fish service different parts of the mantas, with butterfly fish specializing in the bite wounds, while sergeant majors clean the manta’s mouths and cleaner wrasse do the gills.
Tagging of the mantas has established that they only visit the cleaning stations during the day and never at night or dusk/dawn – thus avoiding the main shark activity periods, and at night they seem to move out to deeper waters for feeding purposes.
Diving Mozambique: Tofo’s Manta Ray Code of Conduct
The presence of the manta rays in the Tofo area is clearly a delicately balanced mechanism and while they offer a very special opportunity for divers to see them close-up, the intrusion of divers could easily upset that fine balance.
Therefore the Marine Mega Fauna Foundation and the dive operators have developed a Code of Conduct to be followed by scuba divers when on the reefs that host the cleaning stations.
Divers are not allowed to enter the immediate “comfort zone” of the manta rays at the cleaning stations, but instead there are designated observation areas where the divers are positioned so that the mantas are not intimidated by their presence. What this often means is that the mantas will come and investigate the visitors meaning that the encounters can be just as intimate but very much on their terms.
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