Munk's Devil Ray
Mobula munkiana
A small ray that flies through the sea in schools of thousands — and sometimes right out of it.
Rays are flat cousins of sharks, with skeletons of cartilage and their gills underneath instead of on their sides. Munk's devil ray is the smallest of the devil rays, and it lives only in the eastern Pacific, from Mexico's Gulf of California to Peru. It's famous for gathering in schools of thousands and leaping out of the water, and nobody is quite sure why it does it.
On the conservation status
Vulnerable on the IUCN Red List since 2019. A mother has just one pup at a time, so every ray caught in a fishing net takes a long time to replace. Mexico protects devil rays by law, but some are still caught.
- Width
- Up to about 1.1 m (3.6 ft)
- Weight
- Up to about 25 kg (55 lb)
- Diet
- Tiny floating animals, mostly mysid shrimp
- Babies
- One pup at a time
- Lives
- Only in the eastern Pacific
- Class
- Fish — a ray, not a mammal
The good stuff.
Flying, in and out of the water
Devil rays swim by flapping their fins like wings. In a school, one after another leaps clear of the water and lands with a slap you can hear from a boat.
Why do they jump?
Nobody knows for sure. It may be a way of showing off to mates or of signalling to the rest of the school, and some scientists think it helps shake off parasites. They leap most in the months when they gather to mate.
Horns that aren't horns
The two flaps at the front of its head are cephalic fins. To feed, it unrolls them into scoops that steer food into its mouth. To cruise, it rolls them up into little horns, and that's how devil rays got their name.
The manta's little cousin
Devil rays are close relatives of manta rays, which can be more than 5 metres from wingtip to wingtip. Munk's is the smallest of the family, at about a metre.
One baby at a time
A mother has a single pup, probably after a pregnancy of about a year. Scientists have found a nursery where young ones grow up, in a shallow bay on Isla Espíritu Santo near La Paz — the first ever found for any pygmy devil ray.
Named after a wave scientist
It's named after Walter Munk, an ocean scientist famous for studying waves and tides. The ray was described in 1987 by one of his students, Giuseppe Notarbartolo di Sciara.
Wait, really?
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Its back is mauve-grey, with a dark collar across the back of its head.
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It feeds by filtering tiny shrimp called mysids out of the water with plates in its gills.
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Pups are born in spring and early summer, between April and June.
What it sounds like
Silent, as far as anyone knows. The only noise a school makes is the slap of rays landing after a jump — sometimes hundreds of them.
Where you might see one
The Gulf of California, especially around La Paz, Isla Espíritu Santo and Los Cabos, where the big schools gather. Also the Pacific coast from Central America to Peru.
The trouble
- Getting caught by accident in gill nets and other fishing gear
- Illegal fishing for their gill plates, sold as a medicine that doesn't work
- One pup at a time, so losses add up fast
- Boat strikes and crowding from careless tourism
One real thing
If you ever snorkel near a school, keep your distance and let the rays come to you. Never chase, touch or block them. And tell people about the gill-plate trade: the medicine made from them has never been shown to do anything.
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