Manta Rays in Raja Ampat

  • Mai 7, 2020

Raja Ampat is known as the global epicenter of marine biodiversity. Its nutrient rich waters allow the flourishing of marine life. Raja Ampat has more than 75% of the world’s coral reef species and more than 1600 species of reef fishes. Additionally 17 species of marine mammals and 22 species of sharks. But one of the highlights for divers in Raja Ampat are without doubt the manta rays. The two species are the Reef manta rays (Mobula alfredi) and the Giant manta rays (Mobula birostris). Raja Ampat is one of the few places in the world where visitors can observe both species.

Biology and Behavior of Manta Rays

Manta rays are extraordinary animals, fascinating scientists and divers all over the world. Yet, very little is known about their ecology and behavior, most of the observations being made around coastal cleaning stations.

Manta rays are the largest rays in the world. The Giant manta ray reaches up to 7m disc width and the Reef manta rays up to 5.5m. You can differentiate those two species mostly by the color and shape of the pattern on their back. Also the spot patterns on their belly are relevant (see pictures). Most of the mantas are black on their back and white on their belly. But some black (melanistic) and white (leucistic) polymorphs also exists.

a black and white giant manta ray see from the top in Raja Ampat

Giant manta (Mobula birostris) seen from the top. Do you notice the “T shape” black pattern surrounded by the bright white color? Image by Debbie Arriaga, Our Ocean Images

 

the belly of a giant manta ray

Giant manta (Mobula birostris) seen from the belly. You can notice a dark mouth, no spot between the gills but large spots right under the gills and smaller ones between the gills and the tail. You can also observe the large dark edge of pectoral fins. Image by Debbie Arriaga, Our Ocean Images

 

belly of a mainly white Reef manta ray in Raja Ampat

Reef manta (Mobula alfredi) seen from the belly. Do you notice the spot patterns between the gills? Her mouth and pectoral wings edge are also much lighter than the Giant manta ray. Image by Jerry Arriaga, Our Ocean Images

 

reef manta ray from the top

Reef manta (Mobula alfredi) from the top. Here you can observe a “Y shape” pattern and a lesser bright white color. Image donated by MMF.

Like many elasmobranchs, manta rays spend their whole life in motion, allowing them to breath and feed by filtering water. In fact, manta rays use their cephalic fins to direct plankton directly into their mouth. They use various feeding strategies. Among the most impressive ones barrel roll feeding, bottom feeding, chain feeding or again cyclone feeding.

one manta ray following the other in a behavoir called cooperative feeding

An example of feeding behavior. During co-operative feeding, one manta will swim behind another and catch the zooplankton that jumps out of the way of the first manta, straight into the mouth of the second manta.
Image donated by Dr Andrea Marshall, MMF

Manta rays have disproportionately large brain compared to their body weight (ten times larger than a whale shark’s!). With especially developed areas for learning, problem solving and communicating. A 2016 study also showed that mantas might actually be self-aware. This would make them one of the most intelligent marine species! We don’t know yet why filter feeders would develop such an extraordinary brain. Studies show complex social behavior, including courtship and mating events that lucky divers might be able to witness.

several manta rays swimming behinf one another in raja ampat, as a courtship ritual

As part of an elaborate courtship ritual, female manta rays lead males on a wild chase through the sea. Image donated by Dr Andrea Marshall, MMF

Conservation of Manta Rays

Both manta rays are listed on the IUCN (International Union for the Conservation of Nature) Red List of threatened species as Vulnerable. The greatest threats for the conservation of mantas and more largely the family of mobulids are target and incidental fisheries. With an increasing demand of gill plates for Asian medicinal markets, the populations of manta rays have decreased dramatically those past decades. They are also caught accidentally in fishing nets or line, inflecting severe wounds or death.

Manta rays now benefit from an international protection, with the inclusion of both species in CMS (Convention on Migratory Species) (Appendix 1 and 2) in 2011 and in CITES (Convention on International Trade of Endangered Species) (Appendix 2) in 2013. In 2014, Indonesia declared its whole exclusive economic zone as a manta ray sanctuary, the largest in the world. Here, Raja Ampat benefits of 8 marine protected areas (MPA). They cover the main known functional zones for manta rays and ensure their protection. Papua Explorers Dive Resort is located in one of the most famous one of the region, the Dampier straight MPA.

Concerned about the increasing interest for manta diving, Papua Explorers Eco Resort and several other local actors initiated the creation of the Manta Sandy Patrol Station, near the famous Manta Sandy cleaning station. Together we adapted the dive site with demarcations and buoys. This allows a safe diving with a minimum impact on manta rays. A code of conduct displays the good practices that boats and divers should adopt. Additionally patrols ensure the respect of those rules.

Manta Rays in Raja Ampat

Raja Ampat is one of the few locations in the world where both Reef mantas and Giant mantas can be observed. It is also the best place in the world to observe melanistic mantas (black mantas). These represent 41% of the manta population.

Manta rays usually follow the northwest monsoons, from October/November to April/May, when deep-water upwelling trigger plankton blooms. Reef mantas are the first ones we can encounter (October-March) while the Giant mantas usually arrive later (February-may).

We can observe them both at cleaning stations located inside the Dampier Strait, but rarely together. For Reef mantas, our favorite dive site is Manta Ridge cleaning station. Here they also meet for social interactions like playing or mating. This season, we witnessed there more than 100 individuals at the same time! We also often see them in Manta Sandy, which benefit from easier conditions for beginners and snorkelers. Manta Sandy has been equipped with demarcations to ensure safe and responsible diving.  Now it is one of Raja Ampat most famous dive sites! We see the more discrete Giant mantas mostly at Blue magic and Cape Kri. These are two of our most fishy dive sites and also amazing to explore outside of the manta season!

Anyway, we can actually see manta rays anywhere in the Dampier strait during the manta season! Most of our manta dive site are located between 15 and 30 minutes away from the resort.

Diving with Manta Rays in Raja Ampat

Rays are smart and peaceful animals that like to interact with divers. It is not rare to see them passing just on top of your head to play with your bubbles! All you have to do is to wait peacefully and enjoy the show. Of course, you must respect their space. If you swim straight right at them or after them they might just swim away!

During our dives, we position ourselves outside of cleaning stations. Then we observe the magical hovering of those giants while tiny fishes meticulously clean them. If you are lucky, you might as well observe them feeding into circle or again chasing each other in a mating ballet. Copying their smooth, slow movements is the best way to behave around them. Just let them come to you!

Our Manta Rays Monitoring Programme

Papua Explorers Foundation together with the Marine Megafauna Foundation is running a research programme on manta rays’ population in Raja Ampat. It engages local community members and international guests in collecting essential data to understand the complex and still poorly known manta rays’ ecology and behavior. This knowledge is key to support local, national, and international actions for the protection of manta rays.

For this programme, we are building a photographic catalogue of manta rays that allows us to follow individual during their life. The unique spot pattern on their belly is like a fingerprint that allows us to identify each of them!

Do you want to participate?

Join us for one of our manta dive and share with us your picture of manta’s belly!

More information on our programme?

Contact Sophie Azam, our manager at SEA Centre – Papua Explorers Foundation



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