Diving With Giant Manta Rays In Thailand
The magnificent giant manta rays are regular visitors to Thailand but despite their enormous size can be difficult to find around Phuket. These giant ocean creatures are for many scuba divers the ultimate underwater encounter. If you’ve ever been fortunate enough to spend time with these enigmatic rays then you’ll know why.
How Big Are Giant Manta Rays?
They’re big! The largest ever recorded had a whopping wingspan of 9m. That’s not normal but they still average a huge 5 – 7m with the females being slightly larger than the males. Unsurprisingly giant manta rays (manta birostris) are the largest rays and can weigh over 1,000kg. Even at birth the pups have a wingspan of over 1m which already makes them larger than most rays. They have a relatively short lifespan of 20 years compared to a whale sharks 100 years +. So getting that big in that time is very impressive.
Ocean Wanderers?
It was long presumed that giant manta rays wandered 1,000’s of km around the worlds oceans but new studies suggest otherwise. Populations are much more local than at first thought. Giant manta rays were tagged for 6 months in different locations, the tag data revealed a surprisingly small travel area of only a few hundred km’s. Great for study but it does make populations more vulnerable to local hunting. Our giant manta rays in Thailand are not going to be replaced by others so it’s paramount that we protect them. Supporting great projects like Thailand Manta Trust is absolutely vital.
What Do Manta Rays Eat?
This will come as a surprise to most, less than 30% of their diet consists of surface plankton. Scientists have determined by muscle biopsy that the remainder is made from organisms dwelling in the mesopelagic zone. That’s science talk for depths between 200 – 1,000m. They could be much more active predators than we first thought and feed on small/medium sized fish and crustaceans. Again this does draw slight concerns, this mesopelagic zone is the next target for fisheries. The depletion of resources in this zone could have a significant impact on global populations.
So Why Do We See Them On Shallow Reefs?
For sure one reason is for a good clean, cleaner wrasse and butterfly fish congregate on certain areas of reef and wait for the manta rays to deliver their food. Dead skin and parasites are expertly removed by the army of cleaners leaving the manta ray clean and healthy. A potential second reason is sunbathing. Manta rays like most fish are ectotherms, meaning their body temperature is determined by the surrounding water. After long feeding forays in deep, cooler water they may visit shallow reefs to warm up. Whale sharks and sunfish display similar recovery behaviour in warmer surface waters. We often see all of these species near the surface away from coral reefs and cleaning stations.
Where Can I See Giant Manta Rays In Thailand?
We’re fortunate enough to have quite a few Phuket scuba diving sites that are visited by manta rays. On our day trips we have Racha Noi, especially the south tip. However the liveaboards in both the north and south andaman offer a far better chance. Koh Bon and Koh Tachai have regular sightings between October and May as do the southern dive sites of Hin Daeng and Hin Muang.
There’s of course no guarantee on any of the dive sites but who better than the local experts to give you up to date advice on where to go. Contact Local Dive Thailand and give yourself the very best chance of an encounter with these magnificent ocean giants.
By Justin Hartrey
Posted in Rare & Peculiar Critters on .
