Episode 139 – Giant Manta Ray: A Focused Fish

“…and today we’re talking about a buccal pumping pup sucking histotroph in huge chunks. That sentence will only get grosser when you know what those words mean. But more on that later…”

Sometimes the biggest giants are the gentlest giants. But this gentle giant is also a genius giant. While the oceanic manta ray might not be smarter than a fifth-grader, it does use its brain in ways that would make other fish extremely sad and jealous if they had any feelings. In fact, it’s those feelings that make the manta ray a prime candidate for smartest swimming blanket. But when you’re the biggest fish in the pond, you can afford a little self-awareness here in Life, Death, and Taxonomy.

Manta Ray Taxonomy

  • Chondrichthyes is made up of cartilaginous fish like sharks, skates, and rays.
  • Myliobatiformes includes four orders of batoids, which is a superorder of rays.
  • Mobulidae is made up of the largest species of rays.
  • Mobula is also called flying rays because members of the genus breach.

Description of the Manta Ray

Wikipedia says this guy is dorsoventrally flattened, which I suppose means its flattened along the x axis. Dorso is the top and ventral is the bottom.

Unlike other rays and skates with round, pancake bodies, our giant has long wing-like fins, hence the batoid distinction. They’re also called eagle rays for these winged features.

They feature some stark countershading with almost a black color on top with white ventral sides. But Big Ray has white fin tips and two white streaks that come from the front of their head and go towards their back. 

They also have cephalic fins, which are those signature appendages that come from the sides of their head and curve downward and in. They can roll these fins up to form little torpedoes on the front of their faces. These “horns” are what give them the nickname devil ray. When they’re unrolled they funnel plankton into their mouths while feeding.

They also have those infamous tails, but like most manta rays, they have no stinger on the end.

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words measure up into ldtaxonomy at gmail dot com. We don’t have a new measure up Intro this week so we get to hear from an animal and Carlos has to guess what it is. 

  1. Finch
  2. Squirrel
  3. Monkey
  4. Frog


  • They’re around 4.5 m (15 ft) on average but they can go up to 7 m (23 ft).
  • How many manta rays go into the height of a stack of every Finding Nemo DVD sold up to 2006?
  • Hint: Even though monumentally popular movies like Frozen have come out since Marlin adventured to 42 Wallaby Way, Sydney, Finding Nemo remains the highest selling DVD of all time. It may always hold that status, since movies are now released on DVD, Blu Ray, and digitally on day one. I only have the number of copies sold up to 2006.
  • Answer: 5,249 rays. The stack would be 24,000 meters (78,740 feet) high. Finding Nemo sold over 40 million copies and DVDs are 0.6mm thick.


  • The heaviest rays can be up to 3,000 kg (6,600 lb).
  • How many clownfish go into the weight of a giant ray?
  • Hint: A clownfish is considerably smaller than a human clown.
  • 11,974 clownfish. A clownfish is about 250 grams.

Manta Ray Fast Facts

The giant manta ray loves the open ocean and the feel of the currents on its cephalic fins. They prefer tropical waters far from land but they may come farther inland sometimes. In deep open water they pick a direction and just swim in a straight line until they find food. As with many open ocean creatures, we don’t have complete knowledge of their behavior and habits. 

It’s thought that zooplankton make up a significant big part of the manta ray diet. When they find food they swim around it to corral it into a cluster and then go through it and filter feed. However, it was later discovered that as much as 73 percent of their diet is from deep water fish.

Like some sharks, manta rays give birth to live young. Fertilized eggs develop and hatch in the female’s oviduct. The hatched pups in the oviduct receive nutrients from milky, uterine secretions called histotroph. Unlike mammals that also give birth to live young, rays don’t have a placenta, so babies aren’t hooked to the mother’s life support systems. So they need to get oxygen through buccal pumping. 

Pups are born at around 20 pounds with a disc size of more than four feet! They come out looking pretty much the same as an adult but smaller.

The giant manta ray is so big that it has very few natural predators except for some sharks and cetaceans, including our friend the orca.

Manta Ray Major Fact: An Intelligent Fish

So when you think of intelligent animals, you don’t usually think about fish. Probably dogs, bears, birds, elephants, primates, octopuses, and dolphins, but not fish. In fact, a lot of people who have a problem with eating animals don’t really have a problem with fish.

They’re dumb and ugly, right? 

Well, I don’t want to yoke anyone’s yak, so I can’t speak for the ugly part. But the manta ray is one fish that doesn’t fall into the dumb category.

They actually have the largest brains of any fish, even proportional to their size.

Outside of being social animals (meaning they recognize and interact with members of their own species in a meaningful way), the manta ray even regularly uses things like cleaning stations to have small fish remove parasites.

But the real test of intelligence in an animal is consciousness, or self-awareness.

What Does Self-Aware Mean?

Most animals aren’t self-aware, meaning they don’t imagine themselves as separate entities in the world around them. There’s just them vs everything else. Which is why most animals’ actions are guided by either instinct or just plain selfishness.

Having this consciousness is tough to prove for a fish, since their habits and gestures are so different from those of a mammal. But one good test they use is the mirror self-recognition test (or MSR) – meaning how does this animal act in front of a mirror.

Most animals completely ignore it.

Social animals will assume that it’s a different member of their species and interact in a social way (usually aggressively). This includes dogs and cats. But self-aware animals will recognize the image in the mirror as a reflection of themselves.

Apes will use a mirror to check their fur in places they can’t see and elephants will inspect themselves with their trunk or touch places that they could only see through the mirror.

When MSR was tested with mantas, they placed a mirror in the enclosure of two rays.

As scientists observed, the rays stopped interacting with each other and instead started spending most of their time in front of the mirror. They would blow bubbles into it and check their undersides.

They didn’t show any signs of social behavior (meeting another ray). Because mantas actually expand and contract their spots when they meet another manta. 

The conclusion is that mantas have complex brains that allow for a consciousness only seen in a rare selection of animals – none of which are fish.

Ending: So spread your cephalic fins, practice good oceanic hygiene, and take a good long look at yourself in the mirror or self-awareness like the manta ray here in Life, Death, and Taxonomy.