All About Mantas

Read below to find out more about what a Manta Ray is, where it lives and why we need to protect them!
What exactly is a Manta Ray? 
Manta rays belong to the taxonomic family Mobulidae. Mobulidae are closely related to sharks! This family contains eleven species of plankton-eating rays. Within this family there are two genera, Mobula and Manta. When we say “manta ray”, we are usually referring to species in the Manta genera. Mantas in the Mobula genus are referred to as “devil rays”, and are similar in appearance to Manta Rays. In the genus Manta there are two species, Manta birostris (the giant oceanic manta) and Manta alfredi (the resident reef manta). These two species have much in common, but a few important differences in life history exist between the two. Guam has a resident population of reef mantas, but little is known about Guam’s oceanic mantas.

What do we eat?

Despite their status as an ocean giant, manta rays feed on some of the smallest organisms in the sea! They are planktivores, feeding especially on zooplankton; tiny animals such copepods, mysid shrimps and arrow worms. Mantas are known to make seasonal migrations in order to take advantage of particularly abundant areas of food.

How big do we grow?

Oceanic mantas (M.birostris) are the bigger of the two manta species; reaching a wing span (that’s wing tip to wing tip) of up to 7 metres (23ft)! A large oceanic manta might weigh in at up to 2 tonnes (4,440 lbs), making them a real ocean giant! Although smaller than the oceanic mantas, the reef mantas (M.alfredi) are still pretty big fishes, growing to an average wing span of 3-3.5 metres (9-11.5ft) and a possible maximum of 4.5 metres (15ft), reaching weights of up to 1.4 tonnes (3,100 lbs). In both species the wing span is roughly 2.2 times the length of the body.

Where do we live?

Both species live pelagic lives in the open ocean, visiting reefs to feed and be cleaned. However, oceanic mantas have the wider geographic range of the two species occurring in tropical, sub-tropical and temperate waters. This species is more migratory in its nature, commonly sighted along productive coastlines with regular upwellings, oceanic island groups and offshore pinnacles and seamounts. The resident reef mantas are more commonly sighted inshore around coral reefs, tropical island groups, atolls and bays, as well as along productive coastlines. As the name suggests, this species is more resident to tropical waters with smaller home ranges. Around Micronesia, both species of mantas can be found, although population studies on each species are relatively rare.


Manta Anatomy

Manta Rays have skeletons made of cartilage instead of bones (like Sharks & Stingrays!). LIke sharks, you can tell a male and female manta ray apart by looking for the presence of claspers (the male sex organ). Mantas have gills on their underside which pull oxygen from the incoming water. Despite the popular misconception, manta rays do NOT have functioning spines like stingrays.

Manta Ray Identification

Did you know that Manta Rays have unique markings that seperate them from other mantas? These spots, patterns and shadings are found on their belly, and allow scientists to distinguish between individuals. This kind of information is key when doing population studies, and can also help researchers monitor manta ray health. Click the button below to learn about Guam’s mantas and how you can tell them apart!

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