Spend enough time in the tropical Pacific and you’ll spot plenty of manta rays. But which species: the oceanic manta ray (Manta birostris) or reef manta ray (Manta alfredi)?

Easily distinguished from the eagle ray — which has spots on its dorsal side and a rounded snout — these species can be tough to tell apart.

Size

First, look at the manta’s disc width. Oceanic manta rays tend to be about 2 feet larger on average than reef manta rays, so if it’s a monster, you might be sharing the water with an oceanic manta ray.

Dorsal Coloration

Take a look at the dorsal side — or top — of the manta. Both species have dorsal surfaces with whitish patches near their shoulder area. If the white patch is a little less defined with a gradient effect and forms a V or Y in black at the top of the manta’s head, it is likely a reef manta ray. But if the well-defined white patches form a T in black, it is likely an oceanic manta ray.

Spots

The oceanic manta has fewer spots on its ventral surface — or belly — except for a small group that’s usually found near its tail. Reef mantas can be found with spots covering their ventral surfaces.

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