Cephalic fin or cephalic fun: insights into manta ray behavior


If your pet could talk, what would it say to you?

My dog Nigel lived with me at Eckerd College, so I think he would definitely ask to visit his fellow ruff ryders Marley on Kappa Field, Lulu in Maryland, and Cooper in New York, and likely mention that humans are the weirdest animals to ever live on this planet.
— Michelle

Elephant trunks. Primate feet. Beaver tails. What do they have in common?

All of these structures are multifunctional across several key aspects of a species’ life: used in foraging, communication, sensing, reproduction, steering… the list goes on. They all represent one brilliant body part that provides a wide range of uses in these derived, or ‘advanced’ animals. 

And there may be another example of this in the marine world.

What do you think of when you hear the words ‘devil fish’? A fish named because its’ horn-like facial structures resemble the silhouette of a devil? Back in the 1700s when these rays were first described, that was unfortunately the first thing that came to mind, and they became known as the Devil Ray family (family Mobulidae). If I didn't know much about these wonderful rays, and all I knew was that they remind one of a devil, I certainly wouldn't want to get in the water with one, let alone protect them. But the Devil Ray is less sinister than you think.

A giant manta ray glides slowly past looking into the camera, with the cephalic fins rolled up. Photo credit: Michelle Carpenter

A giant manta ray glides slowly past looking into the camera, with the cephalic fins rolled up. Photo credit: Michelle Carpenter

These sophisticated ‘devil horns’ are called cephalic fins: fins on manta and mobula ray faces, which push zooplankton (tiny marine animals) into their mouth during filter feeding. Manta rays evolved a large cephalic fin size and, mysteriously, use them across many different behaviors when not actively feeding, which the mobula rays have not been seen to do, suggesting they have more diverse uses than just feeding. But we’ll dive more into that shortly.

Every individual manta ray can be identified by the unique belly spot pattern, like a human fingerprint. Photo credit: Michelle Carpenter

Every individual manta ray can be identified by the unique belly spot pattern, like a human fingerprint. Photo credit: Michelle Carpenter

Scientists have come a long way since that disagreeable naming of the Mobulids; the past 20 years of pioneering manta research has revealed that these incredible animals can be broken up into 3 species - the reef manta, the giant manta, and one species currently being described) - and can be identified individually by their belly spot patterns. These rays have the largest brain to body size ratio of all fish, and are social, charismatic, highly complex beings.

Amazingly, based on personal and global scientific observations, the cephalic fins may play a key role in these social interactions and intricate behaviors. But these are merely initial observations, inferences, and educated guesses, and the scientific process is a lengthy procedure. We cannot be certain what the extent of cephalic fin use is until we approach the idea comprehensively. Science!

A mating train of reef manta rays. The lead female swims with rolled up cephalic fins while the males that follow remain unrolled. Photo credit: Michelle Carpenter

This is what I'm getting myself into for my Masters degree (MSc) at the University of Cape Town (UCT) and Marine Action Research (MAR) in Zavora, Mozambique. My research documents both key aspects of Zavora’s reef manta population and their behavior. Zavora is not an easy place for research due to its remote, inaccessible location, but the experiences in this special place quickly make up for it. Mozambique is where I originally became permanently fascinated by mantas, and more importantly, is an area in which the manta population is under serious threat, facing local extinction. 

As one of the first behavioral studies on wild reef manta rays, we are in the primary stages of this research, by collecting and analyzing loads of videography to get to the bottom of the mystery of manta cephalic fins.

Manta rays visit cleaning stations together as a social activity. Photo credit: Michelle Carpenter

Manta rays visit cleaning stations together as a social activity. Photo credit: Michelle Carpenter

Collecting images of the belly spot patterning for population data and video for behavioral research. Photo credit: Guillaume Dupuy

Collecting images of the belly spot patterning for population data and video for behavioral research. Photo credit: Guillaume Dupuy

What additional functions might they have? Thus far, we have identified 3 possibilities:

Steering

Sensing.

Communication. Either between individuals, or perhaps to signal other species.

Already we are noticing not only increased movements in the presence of other mantas and human divers, but also varying types of movements, suggesting that these structures play an even more complex role than previously thought.

To play the devil’s advocate (no pun intented), it is possible these cephalic fin movements outside of feeding could be involuntary and us scientists have been hallucinating this whole time; this is what we call a null hypothesis. But we must see what the data reveals. We’re using videography and processing this data in software to observe different scenarios in which a manta might move the cephalic fins.

A reef manta flips open one cephalic fin while swimming past, potentially a sensory or communication function. Photo credit: Andrea Marshall

A reef manta flips open one cephalic fin while swimming past, potentially a sensory or communication function. Photo credit: Andrea Marshall

So why should we care about manta rays, let alone their cephalic fins?

Manta rays are an iconic and flagship species, generating millions of dollars every year to developing countries via ecotourism, therefore supporting marine conservation. Both species are listed on the International Union for the Conservation of Nature (IUCN) due to global population declines due to numerous threats: increasing direct pressure from both Chinese and artisanal fisheries, indirect fishing from gill netting and longlines, and rapid, unmanaged tourism. Individuals that survive fisheries encounters often bear cephalic fin injuries, and even in protected locations such as Hawaii, 10% of the population have amputated cephalic fins.

Pictured above: ‘Buddy,’ a manta from Indonesia with a cephalic fin stuck outwards (left), and a manta with both fins are amputated (Right, Mozambique). Both: Michelle Carpenter

Despite their charisma and economic importance to the country, mantas remain unprotected in Mozambique. All these factors contribute to a shocking 98% decline in sightings of reef mantas reported in Tofo, ~90 km North of Zavora. However, the 10-year database in Zavora does not reveal the same decline, suggesting that Zavora Bay is a crucial sight for these vulnerable reef mantas. Recognizing critical sites gives an opportunity for conservation management via marine protected areas (MPAs) or national park implementation. Our population research will support this notion, while research on the behavior advances our knowledge of the species. Through behavioral studies we hope to stimulate incentive for species protection in Mozambique by showing the complexity of manta cephalic fin use and documenting the prevalence of fisheries injuries.

We don’t give animals enough recognition for their intelligence or awareness. Manta cephalic fins are yet another example of how humans assume animals to lack intelligence, as they were known as ‘devil horns’, and how science can change or advance our perspective, as these fins are potentially used in communication. We share this world with fascinating, incredibly skilled, brilliantly strange, complex beings. We have the chance to live in harmony and recognize their importance, but we must act fast.

A big thank you to my family, supervisors, advisors, friends and supporters of this work and for those that made it possible: Marine Action Research, Zavora Lodge, Formech Inspire, Kraken Lights, the University of Cape Town, and Chasing Tails TV.

All the best,

-Michelle


Like this article? Still have lingering questions? Fill out the form below to ask Michelle your question and receive an answer.

Write your name here *
Write your name here