When a huge black wing slowly glides overhead underwater, most people's first reaction is "Wow, a manta ray!" But did you know that beneath those wings lies an entire family? The world's manta rays and their close relatives — devil rays — add up to 10 species in total. The Editor once assumed a manta ray was simply a big stingray, until reading Field Guide to Manta & Devil Rays of the World, published by international marine conservation organisation Manta Trust, and discovering that every member of this family looks alike yet has its own distinct story.
Manta Trust is the world's most dedicated charitable organisation focused on manta ray research and conservation. In recent years the Editor has covered their research "valuing" the manta rays of the Maldives (feel free to scroll to the further reading at the end for that piece). This time, the Editor has condensed their world field guide into a single article — with dorsal identification illustrations and Manta Trust species videos for every entry — to help you get to know all 10 family members at once, flag which species can be spotted in Taiwan, and highlight the troubles they face.
First, Let's Get the Classification Straight: How Are Manta Rays Categorised?
Manta rays belong to the order Myliobatiformes, a large family comprising around 370 species divided into 12 families of rays. All of today's subjects fall within just one of these families — Mobulidae — and the entire family contains only a single genus, Mobula.
The 10 species within this genus can be broadly divided into two groups:
- 3 "manta rays" (manta): the largest species, the ones that appear most frequently on divers' bucket lists.
- 7 "devil rays": smaller relatives whose paired cephalic fins — which look like devil horns but are actually used to funnel plankton into their mouths — give them their common name.
It's worth noting that all of them are gentle giants that survive entirely on filter-feeding on plankton. That gaping mouth may look intimidating, but they are completely harmless to humans.
The 3 True Manta Rays (Manta)
Oceanic Manta Ray (Mobula birostris, known in Taiwan as 雙吻前口蝠魟)
The giant of the family. Disc width averages 4 to 5 metres, with the largest recorded individual reaching a staggering 6.8 metres and a weight of up to 2,000 kg. Two white shoulder patches on its back form two symmetrical right triangles, leaving a black "T" shape in the centre — the easiest way to tell it apart from the Reef Manta Ray. The inside of its mouth and cephalic fins are black, and there is a small bump at the base of its tail concealing a vestigial tail spine.
As its name suggests, it spends most of its time in the open ocean far from reefs, diving hundreds of metres deep in search of plankton. It lives for around 40 years and is listed as Endangered on the IUCN Red List.
In Taiwan: The Oceanic Manta Ray is not commonly encountered in Taiwan, but fishermen occasionally land one as bycatch — records from Hualien and Taitung exist — and it is the main subject of the Editor's earlier series of reports on Taiwan's manta rays.
Reef Manta Ray (Mobula alfredi, known in Taiwan as 阿氏前口蝠魟)
This is the species divers encounter most often. Disc width averages 3 to 3.5 metres, reaching a maximum of around 4.3 metres and a weight of up to 844 kg — slightly more slender than the Oceanic Manta Ray. The black-and-white boundary on its back is softer and more diffuse, blending into a black "V" shape at the shoulders (remember: Oceanic = T, Reef = V).
It favours relatively shallow coral reef waters around continental coasts and offshore islands, which is why it's more commonly encountered by divers at cleaning stations or feeding hotspots. It also lives for around 40 years and is listed as Vulnerable on the IUCN Red List.
In Taiwan: The Reef Manta Ray is the species Taiwanese divers occasionally encounter in the water, and fishermen sometimes catch it as bycatch as well.
Atlantic Manta Ray (Mobula yarae)
This is the family's "newest member," formally confirmed as a distinct species in July 2025 through genetic analysis after 15 years of debate. Disc width reaches a maximum of around 4.8 metres, with a weight of up to approximately 1,077 kg. Its back also bears the black "T" shoulder patch, but the underside around the gill slits features large, rounded or oval dark blotches.
It is found exclusively in the Caribbean island chain and along the Atlantic coast from Massachusetts down to Brazil, playing an ecological role more similar to the Reef Manta Ray. Scientists believe it evolved from a group of Oceanic Manta Rays that "settled" into Caribbean reef environments long ago.
The 7 Devil Rays (Devil Ray)
Sicklefin Devil Ray (Mobula tarapacana)
The big one among the devil rays, with a maximum disc width of 3.7 metres. Its back is an unusual olive green or brown, the ventral black-and-white boundary is serrated, and there is a prominent ridge running along the dorsal midline. It holds the record as the deepest-diving devil ray, plunging to depths of 2,000 metres where water temperatures drop below 4°C.
Its bicoloured gill plates — white inside, dark outside — fetch the second-highest price on the gill plate trade market after the manta rays, making it the third most heavily traded victim. It is widely distributed in warm Pacific waters including those around Taiwan, and is listed as Critically Endangered on the IUCN Red List.
Spinetail Devil Ray (Mobula mobular, known in Taiwan as 正蝠鱝)
Maximum disc width of around 3.5 metres. Its most recognisable feature is a thick black band across the top of the head running from eye to eye. The back is slate blue with a hint of grey and dark-edged fins, while the underside is bright white; the dorsal fin tip is white, and the tail carries a spine that fishermen often remove. Found in tropical to temperate seas worldwide, including Pacific waters around Taiwan, it is occasionally caught as bycatch in coastal fisheries. It is also one of the most frequently captured devil rays in global fisheries, causing a significant population decline; listed as Critically Endangered on the IUCN Red List.
Bentfin Devil Ray (Mobula thurstoni)
Maximum disc width of around 2 metres, with an average of just 1.35 metres. The back is deep purple to blue-grey, with the same thick black band across the head from eye to eye; the underside shimmers with an iridescent silver or gold sheen. Its signature feature is a clear "double bend" along the anterior margin of the pectoral fins, and it lacks a tail spine. Usually solitary, occasionally forming small groups of 2 to 6 individuals, it appears frequently in Southeast Asian fisheries catches and is listed as Critically Endangered on the IUCN Red List.
Shorthorned Pygmy Devil Ray (Mobula kuhlii)
Entering "pygmy" territory — maximum disc width of 1.34 metres and a weight of just 25 kg. Back colour ranges from purple-grey to chocolate brown, with a dark crescent-shaped "collar" above the spiracles. An agile coastal dweller, it hunts mysid shrimp and juvenile fish in groups of 5 to 15 (sometimes upwards of 50). Found mainly off the coasts of Pakistan, Bangladesh, and Mozambique, and listed as Endangered on the IUCN Red List.
Longhorned Pygmy Devil Ray (Mobula eregoodoo)
Maximum disc width of 1.3 metres, averaging 1.1 metres. Very similar to its shorthorned cousin, but with a noticeably longer neck and longer cephalic fins — the key distinction for identification in catches. The back is brown with dark stripes along the anterior pectoral fin margin, and it lacks a tail spine. Found throughout the Indo-Pacific, it commonly appears in groups of a dozen or more individuals and is relatively frequently caught in Pakistani and Indonesian fisheries; listed as Endangered on the IUCN Red List.
Munk's Pygmy Devil Ray (Mobula munkiana)
Maximum disc width of 1.3 metres, with a purple-grey back and a deep black collar on the head. This species is best known for aggregating in the Gulf of California, Mexico, during certain seasons in schools of up to tens of thousands, and for collectively breaching several metres out of the water — like a vast spray of flying black droplets — for reasons that remain a mystery. Found only along the Eastern Pacific coast, from the Gulf of California down to Peru. Precisely because of its schooling behaviour, it is especially vulnerable to being swept up in one haul by gillnets or purse seines; listed as Vulnerable on the IUCN Red List.
Atlantic Pygmy Devil Ray (Mobula hypostoma)
The final member of the family — average disc width of 1.1 metres and a weight of around 24 kg. Back colour ranges from light brown and grey to black, with very small, nearly circular spiracles. Found in tropical to warm-temperate waters on both sides of the Atlantic, it typically travels in groups of 2 to 10, with a maximum recorded aggregation of 40 individuals. Although not a direct target of fisheries, it is frequently taken as bycatch in longlines and gillnets, and is estimated to have declined by 50% to 79% over three generations; listed as Endangered on the IUCN Red List.
▶ Watch it swim: Manta Trust species spotlight video (Western Atlantic population)
Wait — What About the Spotted Eagle Ray? Why Isn't It on the List?
The Editor knows you're probably wondering: why doesn't the spotted eagle ray — that creature with a back sprinkled in white dots, also called the ocellated eagle ray — appear among these 10 species? Many people confuse it with manta rays, or even assume it's in the same family, but it is actually a distantly related species in a completely different family.
The spotted eagle ray's scientific name is Aetobatus ocellatus, belonging to the family Aetobatidae (formerly merged into Myliobatidae). Although it shares the order Myliobatiformes with today's subjects, the two are in entirely different families — so it has no place on the Mobulidae list. To tell them apart underwater at a glance, just keep these points in mind:
- Look at the head: manta rays and devil rays have their mouths at the very front of the body, flanked by a pair of horn-like cephalic fins; eagle rays have a protruding, duck-bill-shaped snout with no such "horns." Whether or not there's a pair of "horns" on the head is the fastest way to tell.
- Look at feeding behaviour: eagle rays are benthic predators, using that duck-bill to root through sand and their plate-like teeth to crush molluscs and crabs; manta rays and devil rays are gentle giants that filter-feed on plankton with wide-open mouths.
- Look at the pattern: the spotted eagle ray's back is covered in white spots (hence the names "spotted" and "ocellated"); manta rays have two large white shoulder patches, while devil rays are mostly plain with a dark head band.
- Look at the tail: the eagle ray trails a whip-like tail that can be up to three times the length of the disc and carries a venomous spine; the tails of Mobulidae members are comparatively much shorter.
The spotted eagle ray is found throughout Taiwan and across the Indo-Pacific, and is a common star attraction in aquariums. It is also listed as Endangered on the IUCN Red List. So next time you encounter one underwater, check whether it has that pair of "horns" on its head — and you'll never mix them up again.
Knowing Them Is the First Step Toward Conservation
Looking at all 10 species laid out together, the Editor feels genuinely heavy-hearted. Of the 10 species, 3 are Critically Endangered and 4 are Endangered — not a single one is doing well. Their shared greatest threat is the gill plates harvested for so-called "health supplements," compounded by their schooling behaviour that allows nets to sweep up an entire group in one go. And several of these species swim in the Pacific waters right on Taiwan's doorstep.
This is precisely why "knowing them" matters so much. When you can identify underwater whether something is an Oceanic or a Reef Manta Ray, or recognise which devil ray species that eye-to-eye black band belongs to, every encounter becomes that much more meaningful. The Editor has always believed that conservation isn't a distant slogan — it starts with "I can see it clearly, and I care." Before your next dive, save this field guide. You never know when it might come in handy.
Sources
The content of this article is compiled from the world species field guide published by international marine conservation organisation Manta Trust. All species identification illustrations and "species spotlight" videos are the work of Manta Trust, to whom we extend our sincere thanks:
- Manta Trust species overview: Manta and Devil Ray Species
- Individual species detail pages: Manta Trust
- Manta Trust species spotlight video series: Manta Trust YouTube
- Further reading: 《海洋博物誌3｜離岸珊瑚礁》墾丁、台東、蘭嶼、綠島、龜山島、澎湖南方四島，936 種熱帶珊瑚礁生物辨識百科
The hero image for this article is the cover of Manta Trust's Field Guide to Manta & Devil Rays of the World. All species identification illustrations are © Marc Dando / Manta Trust.
